Showing papers on "Sowing published in 1999"

On-farm seed priming in semi-arid agriculture: development and evaluation in maize, rice and chickpea in india using participatory methods

Abstract: Poor crop establishment was identified as a major constraint on rainfed crop production by farmers in the tribal villages of Rajasthan, Gujarat and Madhya Pradesh served by the Krishak Bharati Cooperative (KRIBHCO) Indo-British Rainfed Farming Project (KRIBP). On-farm seed priming with water was chosen as a low cost, low risk intervention appropriate to the farmers' needs. In vitro screening of the effects of priming on the germination of seeds of local and improved varieties of maize, upland rice and chickpea provided ‘safe limits’ – the maximum length of time for which farmers should prime seeds and which, if exceeded, could lead to seed or seedling damage. Recommended safe limits were 24 h for maize and rice and 10 h for chickpea, with only minor varietal differences. These recommendations were then tested in on-station trials in Dahod, Gujarat. Farmer-managed trials were conducted for chickpea in three villages in the rabi (post-monsoon) season in 1995–96; for maize and upland rice in eight villages in the kharif (monsoon) season in 1996; and for maize and chickpea in 15 villages in the 1996--97 rabi season. Farmers modified these recommendations to ‘overnight’ for all three crops. Evaluation of the technology by farmers involved focus group discussions, matrix ranking exercises and two workshops. Direct benefits in all three crops included faster emergence, better stands and a lower incidence of re-sowing, more vigorous plants, better drought tolerance, earlier flowering, earlier harvest and higher grain yield. Indirect benefits reported were earlier sowing of rabi crops because of the shorter duration of the preceding kharif crop, earlier harvesting of rabi crops that allowed earlier migration from the area, with better chance of obtaining off-season work, and increased willingness to use fertilizers because of reduced risk of crop failure. In matrix ranking exercises in four villages in the kharif 1996, 95% of farmers indicated that, even after only one exposure to the technology, they would prime seed in the following season. Similar exercises in four villages in rabi 1996–97 revealed that 100% of collaborating farmers intended to continue seed priming. From 21 villages, 246 farmers attended two workshops to share their experiences of seed priming and resolved to continue with the technology.

Seed mass and the competition/colonization trade-off: a sowing experiment

Abstract: Summary 1 A seed-addition experiment using seven co-occurring annual plant species with a range of seed masses was carried out in a limestone grassland in South Wales. 2 If seedlings compete for establishment sites, then large seed size may confer enhanced competitive ability. However, the simple reciprocal relationship found between seed mass and per capita seed output showed that species producing larger seeds suffer reduced fecundity. Seed size may therefore act as a surrogate in a competition/colonization trade-off. 3 Equal numbers of seeds of all species were sown in a mixture over a range of densities. As sowing density increases, all species should reach a higher proportion of the available microsites. If large-seeded species are the best competitors they are expected to win all the sites they reach, and hence to occupy an increasing proportion of sites as sowing density increases. 4 The three species with the largest seeds made up 49% of individuals at low-density sown plots but 83% of individuals in high-density sown plots. In addition, seed mass and plant density were not correlated in unsown plots, but were strongly correlated in high-density sown plots. However, all small-seeded species maintained a presence in sown plots. 5 Although species were sown at random with respect to one another, individuals were up to five times more likely than expected to have a conspecific as a nearest neighbour. This could be caused by interspecific competition and/or by environmental heterogeneity that favours different species in different patches. 6 The results suggest that seedlings do compete for establishment sites and that large-seeded species generally win when in direct competition. In unsown areas small-seeded species win many sites by forfeit (because large-seeded species are strongly recruitment limited) but there may be a restricted subset of potential sites for which they are the best competitors and which they can win outright.

Seed size and seedling emergence: an allometric relationship and some ecological implications.

Abstract: We develop a geometric model predicting that maximum seedling emergence depth should scale as the cube root of seed weight. We tested the prediction by planting seeds from 17 species ranging in weight from 0.1 to 100 mg at a variety of depths in a sand medium. The species were spread across 16 genera and 13 families, all occurring in fire-prone fynbos shrublands of South Africa. Maximum emergence depth was found to scale allometrically with seed weight with an exponent of 0.334, close to the predicted value. We used the allometry to predict recruitment response to experimentally simulated variation in fire intensity. Five species with small ( 10 mg) seeds were planted at ≤20-mm and 40-mm depths and exposed to low and high heat treatments and a control. The allometric equation predicted that species with large seeds would be able to emerge from a depth of 40 mm but those with small seeds would not. Only 1% of 481 seedlings from small-seeded species emerged from the 40-mm planting compared with 40% of 626 seedlings from the large-seeded group. The simulated fire treatments killed seeds in shallow, but not deeper, soil layers. At simulated high fire intensities, seedling emergence was poor in small-seeded species but good in large-seeded species, with most seedlings emerging from the 40-mm planting depth. Seed size could be a useful general predictor of recruitment success under different fire intensities in this system. We suggest that allometric relationships in plants deserve wider attention as predictive tools.

Adaptation and seed yield of cool season grain legumes in mediterranean environments of south-western australia

Abstract: A range of cool season grain legume species have shown considerable potential for soils unsuitable for the production of narrow-leafed lupin (Lupinus angustifolius L.) at limited sites in the Mediterranean-type envi- ronments of south-western Australia. In this study the adaptation of these grain legume species was compared by measuring crop phenology, growth, and yield in field experiments at a total of 36 sites over 3 seasons, with the aim of identifying species with suitable adaptation and seed yield for specific environments. The grain legumes examined appeared to fall into 3 categories: (i) field pea (Pisum sativum L.), faba bean (Vicia faba L.), common vetch (Vicia sativa L.), and narbon bean (Vicia narbonensis L.) clearly had superior seed yield to the other species over a wide number of sites and years across south-western Australia (mean 1.0n2.3 t/ha); (ii) albus lupin (Lupinus albus L.), desi chickpea (Cicer arietinum L.), and Lathyrus cicera, L. sativus, and L. ochrus produced seed yields of 1n1.3 t/ha; and (iii) red lentil (Lens culinaris L.), bitter vetch (Vicia ervilia), and kabuli chickpea (Cicer arietinum L.) generally produced the lowest yields (0.6n1.0 t/ha). There were clear species · environment interactions. At low-yielding sites ( 6.0 and clay contents >15%. Seed yields were positively correlated with dry matter production at maturity across a number of sites (r 2 = 0.40, P < 0.01). Future improve- ments in seed yield of these species are likely to come from management practices that increase dry matter pro- duction such as increased plant density and early sowing, and through the development of genotypes with greater tolerance to low winter temperatures, and more rapid phenology, canopy development, and dry matter production than existing commercial cultivars.

Drought-induced Changes in Shoot and Root Growth of Young Cotton Plants

Abstract: An understanding of the response of plants to water deficits is important in efforts to model cotton (Gossypium hirsutum L.) growth, estimate irrigation needs, and breed drought-resistant cultivars. This study examined shoot and root growth of a longand a short-season cotton cultivar after a brief drought and subsequent recovery period. Seeds were planted in fritted clay-filled pots in a growth room under fluorescent lights at about 27 (C. Plants were divided at 36 d after planting into drought-treatment and watered-control groups. Plants were sampled after a 13-d drought and again after a 10-d recovery period. There were no treatment-by-genotype interactions. At the end of the drought and recovery, height, leaf P.F. Pace, DEKALB Genetics Corporation, 3100 Sycamore Road, DeKalb, IL 60115; Harry T. Cralle, Department of Soil and Crop Sciences, Texas AM Sherif H. M. El-Halawany (deceased), Cotton Research Institute, Agricultural Research Center, Ministry of Agriculture, Giza, Egypt; J. Tom Cothren , Department of Soil and Crop Sciences, Texas AM Scott A. Senseman, Department of Soil and Crop Sciences, Texas AM Masle and Passioura, 1987). Several studies have shown that drought inhibits cotton canopy development. Krieg and Sung (1986) determined that drought decreases the number of leaves on sympodial branches of cotton. Leaf area of glasshouse-grown cotton also was inhibited when the percentage of soil-available water was less than 51 ± 15% (Rosenthal et al., 1987). Cutler and Rains (1977) concluded that predawn leaf water potentials below $0.5 MPa were accompanied by decreased leaf elongation rate. Leaf expansion of 55-d-old cotton plants slowed after 2 d of withholding water, which meant that leaf growth was more sensitive than root elongation to drought (Ball et al., 1994). Similarly, McMichael and Quisenberry (1991) found that terminal drought decreased the shoot:root ratio. Drought also reduced the growth, development, and distribution of cotton roots (Malik et al., 1979; Taylor, 1983). Root growth of 55-d-old cotton was reduced after 6 d of withholding water (Ball et al., 1994). The number of roots elongating decreased by 35% during the drought. Planting early-maturing cultivars can decrease the amount of water used by cotton, and other traits in future cotton cultivars may further decrease the amount of water used. Quisenberry et al. (1981) found considerable variability for heat tolerance, root growth, dry matter accumulation, and water use efficiency among exotic cotton strains under dryland conditions. Gerik and co-authors (1996) compared two short-season cotton cultivars and found that one, Tamcot HQ95, yielded more than other, GP74, regardless of the level of water stress. They concluded that the photosynthetic capacity of Tamcot HQ95 might be greater than that of GP74. Root elongation during drought may help plants get deeper water, thus avoiding water deficits near the soil surface. Elongation also could reduce the water lost by drainage when precipitation allows recovery after the drought (Ludlow and Muchow, 1990). If, however, water is unavailable deeper in the soil profile, longer roots may reduce shoot dry weight and harvest index by allowing the preferential partitioning of photosynthate to roots at the expense of shoots. This study examined various measures of shoot and root growth of one longand one short-season cotton cultivar after a drought of limited duration and a subsequent recovery period. MATERIALS AND METHODS A long-season cotton, ‘Stoneville 506,’, and a short-season cotton, ‘Tamcot HQ95,’ were planted in pots (9-L volume, 20 cm deep) filled with fritted clay (Absorb-N-Dry, Balcones Co., Flatonia, TX). Filter paper at the bottom of the pots retained the fritted clay while allowing for drainage. Two plants were seeded per pot and were supplied with distilled water every other day for 10 d. The pots were then watered with a nutrient solution of 0.90 g L of 2020-20 NPK fertilizer (Peters Professional All Purpose Plant Food, Spectrum Group, Division of United Industries Corp., St. Louis, MO) until 36 d after planting. This fertilizer was selected because soil tests showed that the fritted clay had very low levels of N, P, and K and that nutrients would be quickly leached from this well-drained soil. Water or nutrient solution, when applied, was added until an excess drained from the bottom of the pot. The experiment 185 JOURNAL OF COTTON SCIENCE, Volume 3, Issue 4, 1999 was conducted in a growth room under fluorescent lights providing a photosynthetic photon flux density of 700 )mol m s for 16 h d. Temperature was maintained at 127 (C. At 36 d after planting, plants were randomly divided into drought-treatment and watered-control groups. The drought-treated plants were not watered for 13 d. At the end of this drought treatment (49 d after planting), control and drought-treated plants were sampled and height, number of nodes, leaf area, and taproot length were measured. Secondary root length of fresh roots was measured by a Comair Root Length Scanner (Commonwealth Aircraft Corp. Ltd, Melbourne, Australia). Leaves, stems, and tap and secondary roots were dried for 48 h at 90 (C before dry weights were determined. The shoot:root weight ratio was calculated from the dry weights. At 49 d after planting, the remaining droughttreated plants were watered during a 10-d recovery period. At 59 d after planting, both treatments were sampled as described above. The experiment was a randomized complete block design with two blocks. Each block had four pots of each cultivar. Each pot had two plants. The experiment was repeated twice. There was no interaction between treatment and experimental run, so data from the two runs were pooled for statistical analysis. The cultivar primary effect was insignificant, so data also were pooled across cultivar. This analysis used the SAS System (SAS Institute, Cary, NC). RESULTS AND DISCUSSION At the end of the drought treatment, droughttreated plants had significantly (P < 0.05) lower height, less leaf area, fewer nodes, and lower dry weights of stems and leaves than did the controls (Table 1). Additionally, the drought-treated plants had a lower shoot:root ratio (Table 2) than did the controls at this sampling, 49 d after planting. There were no differences between the two treatments in the lengths of the secondary roots or in the dry weight of the secondary or taproots at the end of the drought period (Table 3). However, the droughttreated plants had a significantly (P < 0.01) greater tap root length than did the controls at this time (49 d after planting). The taproot dry weight in the drought-treated plants was identical to that of controls, so the drought-related elongation occurred at the expense of taproot thickening. While the drought-treated plants had a taproot dry weight per length of only 0.011 g cm, the corresponding measurement for the well-watered controls were Table 1. Heights and dry weights of stem, leaf area and dry weight, and node number in drought-treated and control plants of Stoneville 506 and Tamcot HQ95 at the end of the drought, 49 d after planting.† Means are followed by standard errors of the mean in parentheses.

Corn Hybrid Response to Planting Date in the Northern Corn Belt

Abstract: Growers frequently are concerned about the response of corn (Zea mays L.) to planting date. Early planting of corn is recommended because full-season hybrids utilize the entire growing season, achieve physiological maturity before a killing frost, and start to dry, thereby increasing profit through reduced drying costs. The objective was to evaluate the influence of planting date and hybrid maturity on corn grain yield and harvest moisture in Wisconsin. Two or three corn hybrids ranging in relative maturity from 80 to 115 d were planted between 19 April and 22 June at six locations in Wisconsin from 1991 to 1994. In southern Wisconsin locations, the optimum planting date for grain yield of full- and shorter-season hybrids ranged between 1 and 7 May, and was still at 95% of optimum between 9 and 18 May. In northern Wisconsin, the optimum planting date for grain yield of hybrids ranged between 8 and 14 May, and was still at 95% of optimum between 15 and 23 May. Grain yield did not change much when corn was planted between 24 April and 8 May. Grain yield of corn planted after 8 May in southern Wisconsin declined at the rate of 0.5 to 1.1% d -1 over the next 2 wk, accelerating to 1.3 to 1.9% d -1 and 2.0 to 2.8% d -1 over the next two 2-wk periods. Grain yield of corn planted after 8 May in northern Wisconsin declined at the rate of 0.2 to 1.7% d -1 over the next 2 wk, accelerating to 1.7 to 2.2% d -1 and 3.2 to 3.8% d -1 over the next two 2-wk periods. The decision to begin planting corn early should be based on soil temperature and field conditions. After 20 April, planting of full-season hybrids should proceed as rapidly as field conditions allow. The date to switch from full-season to shorter-season hybrids depends on numerous factors, including corn price and drying costs, but generally occurs by mid-May in southern and by late May in northern Wisconsin.

Forest Restoration in Abandoned Agricultural Land: a Case Study from East Africa

Abstract: Millions of hectares of tropical forests have been converted to agricultural land and abandoned, so it is important that we understand the process of forest recovery and comprehend how pathways are modified by different types of disturbance in different geographic regions. In a 4-year case study, we quantified the pattern of forest recovery following clearing and 3 years of cultivation of a moist-evergreen forest in Uganda. Long-term observation (746 hours) of frugivore visitation to the regenerating area demonstrated that birds were frequent visitors (5.8 birds/hour), whereas large mammalian frugivores rarely used the area. Frugivore visitation rates facilitated seedling recruitment that averaged 0.51 seedlings/m 2 from 22 tree species by the end of the study. Re- cruitment included species with large seeds, despite the fact that seed-eating rodents were almost twice as abun- dant in the regenerating area than in mature forest. By the end of the study, however, only 20 trees were $ 0.5 m tall, and no trees were $ 2 m tall. This slow recruitment reflected high seedling mortality and dominance of the area by elephant grass ( Pennisetum purpureum ) and the herb Acanthus pubescens . After 4 years, trees $ 0.5 m tall attained a biomass of only 8.92 kg/ha, whereas the biomass of P. purpureum and A. pubescens had reached 35,500 kg/ha and 18,100 kg/ha respectively. We provide an initial assessment of two programs designed to en- hance restoration of abandoned agricultural lands: planting of cuttings to act as dispersal foci and sowing of seeds. Our results showed that density of seedlings growing in the management plot where we sowed seeds (0.35 seedlings/m 2 ) and in the plot where we established cuttings (0.30 seedling/m 2 ) was lower than in the control plot (0.51 seedlings/m 2 ). This East African site was only lightly disturbed, yet tree recovery was occurring slower than in heavily degraded sites described from South America. The rate of recovery seemed to be strongly deter- mined by interactions between tree seedlings and P. purpureum and A. pubescens .

Handbook of agriculture

Abstract: Part 1 Soils: introduction solid soil components the liquid phase of the soil soil chemistry artificial soil, substrates soil disinfection cultivation without soil, hydroponics. Part 2 Fertilizers: general concepts classification of fertilizers chemical fertilizers organic fertilizers application of chemical fertilizers application of organic fertilizers correcting and improving soils deficiencies of nutrient elements. Part 3 Fruit trees: introduction reproduction and propagation of fruit trees climate in fruit cultivation the soil planting fruit trees pruning and training fruit trees cultivation techniques fertilizer application and irrigation flowering, pollination and fruit growth disorders of fruit trees gathering the fruit storage fruit species forestry. Part 4 Defence of cultivated plants: introduction viral parasites parasites of plants animal parasites preventive measures control or curative methods weed control pests and diseases of specific crops. Part 5 Agricultural techniques in extensive crops: introduction the use of cereals the plant cultivation cycles soil preparation sowing tending the crop irrigation agricultural mechanics harvesting storing the grain accidents, weeds, diseases and pests the main extensive crops. Part 6 Horticulture: introduction propagation of horticultural plants sowing soil preparation tending the crop applying fertilizer irrigation application of plant growth regulators alternation and rotation in horticultural crops harvesting horticultural produce storage of horticultural produce characteristics of the main vegetable crops in vitro cultivation in horticulture. Part 7 Greenhouse cultivation: introduction protective structures the influence of environmental factors on greenhouses heating and cooling cultivation systems in greenhouses fertilizer application irrigation fighting pests and diseases - sanitary problems in greenhouses international glossary of terms.

Comparative ecology of seedling recruitment in an oligotrophic wet meadow

Abstract: . For the regeneration niche to contribute to the maintenance of species diversity interspecific differences in sensitivity of seedling recruitment to environmental conditions is assumed. We experimentally tested differences between meadow species for the response of seed germination to chilling, and sensitivity of seedling recruitment to microscale heterogeneity. We also compared the dynamics of seedling recruitment in gaps. Seed germination was tested in standard laboratory germination tests, comparing control seeds with seeds chilled at +4 °C, and at –14°C for one month. Species responses varied from significant increases in germinability after chilling (e.g. Cirsium palustre, Betonica officinalis, Angelica sylvestris) to significant decreases (e.g. Hieracium umbellatum, Succisa pratensis, Selinum carvifolia). In some species, chilling at + 4 °C has a similar effect to chilling at –14 °C, in others the effect of chilling at + 4°C was intermediate, and in some, there was no effect of chilling at + 4°C, but an effect of chilling at –14°C. Different chilling temperatures also affect timing and speed of seed germination under greenhouse conditions. The dynamics of seed germination under field conditions was studied by sowing seeds into artificially created gaps and following their germination, both where the seedlings were removed after emergence and where they were not removed. Species differ in their germination dynamics: they all start late April, but then differentiate from an abrupt maximum and early finish of germination (in the second half of May), to prolonged germination without a marked maximum. Seedling removal increased the total number of germinated seeds, with a marked density dependence at this stage. Seeds were also sown into plots with treatments (1) gaps, sod stripped, above-ground vegetation removed; (2) mown, moss layer removed; (3) mown; (4) untouched control. Seedling emergence was monitored for 3 yr. Seedling recruitment decreased from treatments (1) to (4), but sensitivity differed between species. With increasing seed weight, the difference between gaps and other treatments decreased. The results show that there are considerable differences in seedling recruitment sensitivity between species.

Effects of environmental factors on germination and emergence of amaranthus retroflexus

Abstract: Detailed knowledge about the environmental conditions required for weed seed germination and establishment in soil is an important prerequisite for the development of integrated and biological weed control strategies. Germination and establishment of Amaranthus retroflexus were studied at different temperatures, planting depths, soil types, nitrogen supply, and water potentials. The minimum temperature for seed germination was > 5 C; maximum germination occurred between 35 and 40 C. At temperatures between 25 and 35 C, an additive effect on germination rate was observed when temperature and water availability were increased. For all soils tested, the percentage emergence of seeds placed on the soil surface and 4 cm deep was significantly lower than seeds placed between 0.5 and 3 cm. Emergence in the four sandy soils was generally greater than in the two heavier soils included in the study. There was a highly significant interaction between seed depth and soil type. Plant growth was also greatest in the lighter soils. Plant height, number of leaves, leaf area, fresh and dry weight, and nitrogen and carbon percentage in plant tissues of A. retroflexus increased significantly with increasing soil nitrogen supply.

Direct sowing of Coffea arabica somatic embryos mass-produced in a bioreactor and regeneration of plants

Abstract: The effect of germination conditions on the morphology of Coffea arabica L. somatic embryos mass-produced in a 1-l temporary immersion bioreactor (RITA®) was studied with emphasis on direct sowing in soil. Using germinated embryos, direct sowing resulted in a highly successful conversion of embryos into plants. A culture density above 1600 embryos per 1-l bioreactor positively affected embryo morphology by causing higher embryonic axis elongation (+4–5 mm). At this density, the addition of a high concentration of sucrose (234 mM) 2 weeks before sowing promoted an increase in effective plant conversion in soil (78%) and a vigorous vegetative growth of the resulting plants. Furthermore, direct sowing reduced handling time to 13% and shelving area requirements to 6.3% of the values obtained by conventional acclimatization of plants developed on gel media.

Rodent seed predation and seedling recruitment in mesic grassland.

Abstract: Seedling recruitment of two grasses (Arrhenatherum elatius and Festuca rubra) and two herbs (Centaurea nigra and Rumex acetosa) was measured in areas with and without rodents to which seeds of each species were sown at three seed densities (1000, 10,000 and 50,000 seeds m−2) in two seasons (spring and autumn 1995). Seed removal was measured for 10-day periods and the fate of seedlings was followed for 15 months after sowing. The proportion of seed removed ranged from 6 to 85% and increased with increasing seed density for each species. Rodents had no effect on seedling emergence or survival in the spring sowing. In the autumn sowing, rodents reduced seedling emergence of all four species sown at 1000 and 10,000 seeds m−2 but had no impact at 50,000 seeds m−2, presumably because of microsite limitation. We suggest the difference between spring and autumn arose because emergence was seed limited in autumn but microsite limited in spring; microsite availability was higher in autumn because a summer drought killed plants, reduced plant biomass and opened up the sward. Fifteen months after the autumn sowing, fewer A. elatius and C. nigra seedlings survived on plots exposed to rodents. This result reflected not only the reduced seedling emergence but also increased seedling mortality (seedling herbivory) in sites exposed to rodents. In contrast, F. rubra and R.acteosa showed density-dependent seedling survival which compensated for initial differences in seedling emergence, so that no effect of rodents remained after 15 months. The results suggest that rodent seed predation and seedling herbivory exert strong effects on seedling recruitment of A.elatius and C. nigra when recruitment conditions are favourable (conditions that lead to high microsite availability) and may contribute to both species being maintained at low densities in the grassland. The results also demonstrate that highly significant impacts of rodent seed predation at the seedling emergence stage can disappear by the time of plant maturation.

Comparing the effectiveness of radish cover crop, oilseed rape volunteers and oilseed rape residues incorporation for reducing nitrate leaching

Abstract: The soil water and N dynamics have been studied during two long fallow periods (between wheat or oilseed rape and a spring crop) in a field experiment in Châlons-en-Champagne (eastern France, 48°50′ N, 2°15′ E). The experiment involved frequent measurements of soil water, soil mineral N, dry matter and N uptake by cover crops. Water and N budgets were established using Ritchie's model for calculating evapotranspiration in cropped soils and a model (LIXIM) for calculating water drainage, N leaching and N mineralisation in bare soils. During the first autumn and winter, a radish cover crop (grown from September 1994 to January 1995) was compared to a bare soil. During the second period (July 1995 to April 1996), a comparison was carried out between (i) oilseed rape volunteers, (ii) bare soil with two types of oilseed rape residues incorporated into the soil (R0 and R270 residues) and (iii) bare soil without residues incorporation. R0 and R270 residues came from two preceding oilseed rape crops which received two rates of N fertilizer (0 and 270 kg N ha-1). Soil mineral N content was markedly reduced by the presence of radish cover crop or oilseed rape volunteers during autumn. The calculated actual evapotranspiration (AET) did not differ much between treatments, meaning that the transpiration by the cover crop or volunteers was relatively low (100–150 L kg-1 of dry matter). Consequently, nitrate leaching was reduced during the rest of the winter and spring as well as nitrate concentration in the percolating water: 45 vs. 91 mg NO3 - L-1 for radish cover crop and bare soil, respectively. The incorporation of oilseed rape residues to soil also exerted a beneficial but smaller action on reducing the nitrate content in the soil. This effect was due to extra N immobilisation which reached a maximum of about 20 kg N ha-1 in mid-autumn for both types of residues. Nine months after the incorporation of the oilseed rape residues, and comparing to the control soil without residues incorporation, N rich residues induced a significant positive N net effect (+ 9 kg N ha-1) corresponding to 10% of N added whereas for N poor residues no net effect was still obtained at the end of experiment (−3 kg N ha-1, not significantly different from 0). To reduce nitrate leaching during long fallow periods, it is necessary to promote techniques leading to decrease mineral-N contents in the soil during autumn before the drainage period, such as (i) residue incorporation after harvest (without fertiliser-N) and (ii) allowing volunteers to grow or sowing a cover crop just after the harvest of the last main crop.

Performance of Sweet and Forage Sorghum Grown Continuously, Double-Cropped with Winter Rye, or in Rotation with Soybean and Maize

Abstract: Double-cropping sorghum [Sorghum bicolor (L.) Moench] with winter rye (Secale cereale L.) could increase annual dry matter production in the North-Central region of the USA and reduce soil erosion and other environmental concerns. We conducted this study to compare yield, chemical composition, erosion potential, and economics of sorghum grown continuously (sole crop), in a 3-yr rotation with maize (Zea mays L.) and soybean [Glycine max (L.) Merr.], or double-cropped with winter rye (rye-sorghum). The experiment was on a Typic Calciaquoll soil in central Iowa with a slope of less than 1and on mixed Vertic Argiaquoll, Typic Hapludoll, and Aquertic Argiudoll soils in southern Iowa with 2 to 7% slope. Applied N moderately affected sole-cropped sorghum, with yields of 13.5, 16.1, 16.9, and 15.9 t ha -1 when fertilized with 0, 70, 140, and 280 kg ha ' N, respectively, Rye-sorghum was highly responsive to N, with combined yields at 72, 84, 95, and 110of sole-cropped sorghum fertilized with the same annual rate of N. Drought dramatically reduced rye-sorghum yields. Sole-cropped sweet sorghum had yields similar to sweet sorghum grown in the 3-yr rotation. Environmental conditions associated with years and locations affected fiber components, N, and total nonstructural carbohydrate concentrations of sorghum. Use of the Universal Soil Loss Equation revealed that planting rye before sorghum would reduce estimated soil loss at both h locations, but the loss was still unacceptably high on the sloping soil in southern Iowa (22 l ha -1 ). An economic partial budget showed that ryesorghum cost $147 ha -1 more to produce than sole-cropped sorghum. We conclude that, if winter rye is to be grown as a double crop with sorghum in the North-Central region, it will likely be because of its positive influence on the environment and not because of potential for improved yield.

Initiation of root growth stimulation by Azospirillum lipoferum CRT1 during maize seed germination

Abstract: Maize seeds were inoculated with a commercial inoculant containing 1.3 × 107 Azospirillum lipoferum CRT1 cells. After 24 or 48 h, bacteria were washed from the seed surface. Washed and unwashed seeds were then planted in pots containing perlite and grown for 28 days under greenhouse conditions. Whatever the density of Azospirillum at planting, the number of these bacteria at the end of the experiment was similar (1.9-8.0 × 107 bacteria·plant-1). However, comparison of root surface areas of the plants were different depending on the period of contact between seeds and the density of the inoculum. Twenty-four hours of contact was not sufficient to increase root growth surface areas. Contact for 48 h permitted us to obtain root surface areas comparable with those measured after a continuous contact. These results showed that in order to promote maize root surface areas, an optimal density of Azospirillum is not required during the whole cultural cycle. This optimal density is indispensable only up to the eme...

Winter Rye Cover Crop Following Soybean Under Conservation Tillage: Residual Soil Nitrate

Abstract: Use of a winter rye (Secale cereale L.) cover crop following soybean [Glycine max (L.) Merr.] has been shown to reduce the soil erosion potential in a corn (Zea mays L.)-soybean rotation system, but little is known about the effect of rye on residual soil NO 3 -N (RSN). An irrigated field study was conducted for 4 yr on a Sharpsburg silly clay loam (fine, smectitic, mesic Typic Argiudoll) to compare crop rotation and winter rye cover crop following soybean effects on RSN under several tillage practices and N fertilization rates. Treatments each year were (i) tillage: no-till or disk; (ii) rotation: corn following soybean/rye (Cbr) or soybean/rye following corn (BRc), corn following soybean (Cb) or soybean following corn (Bc), and corn following corn (Cc); and (iii) N rate: 0, 100, and 300 kg N ha 1 (applied to corn). Rye in the Chr/BRc rotation was planted in the fall following soybean harvest and chemically killed in the spring of the following year prior to corn planting. Each spring, before tillage and N application, RSN was determined to a depth of 1.5 m, at 30-cm intervals. The net spring-to-spring change in RSN between subsequent spring seasons was computed for each plot, and annual aboveground N uptake for rye, corn, and soybean were determined. Rye, rotation, N rate, and tillage significantly influenced RSN in the top 1.5 m of soil. The presence of rye (BRc) reduced total spring RSN between 18 and 33% prior to corn planting in 2 of the 3 yr, compared with the no-rye system (Bc), as rye immobilized from 42 to 48 kg N ha ' in aboveground dry matter. Recycling of N in high-yielding rye cover crop residues led to an increase in RSN accumulation after corn in the succeeding spring. Up to 277 kg RSN ha 1 accumulated at high rates of N following corn in the Cbr rotation, compared with 67 kg RSN ha 1 in the norye system (Cb) in 1992. Regardless of the presence of rye, significant accumulation of RSN occurred following corn in the rotation sequence, while RSN declined following soybean, Less RSN was found in the top 1.5 m of soil under continuous than rotation corn, and disking tended to increase NO 3 accumulation in rotation systems at high rates of N application. Although RSN declines following a rye cover crop, the ready release of this immobilized N suggests that some N credit should be given, reducing N recommendation for corn following winter rye cover, to minimize potential NO 3 leaching under corn-soybean/rye rotations.

Changes in germinability, dormancy and viability of Amaranthus retroflexus as affected by depth and duration of burial

Abstract: Changes in dormancy and viability of Amaranthus retroflexus seeds were examined after placement in pots that were buried in the field. Seeds were placed in woven nylon envelopes on the soil surface or buried at depths of 2.5, 5 or 10 cm. After 1, 3, 6, 9 and 12 months seeds were exhumed and their germinability was tested to assess changes in dormancy and viability. Depletion of seed stocks placed on the soil surface was partly because of in situ germination that did not exceed 21% and did not vary significantly over the 12-month study period. Less germination of buried seeds occurred in situ, and seeds that did not germinate appeared to acquire dormancy. Exhumed seeds germinated readily; germinability was linearly related to the depth of burial, with those retrieved from the surface germinating least. Cyclical changes in germinability occurred during the 12-month burial period, but this influence was identical for seeds buried at all depths. Germinability was greatest after periods with the lowest mean monthly temperatures and least during the hottest periods. The stimulation of remaining ungerminated seeds exhumed at each period, by the addition of ethephon to the germination medium, provided further evidence of a seasonal acquisition of dormancy, and it was concluded that other unknown factors besides cyclical changes in seasonal temperature were responsible. Irrespective of placement, all seeds lost viability at an exponential rate over time. However, the decline was most rapid for those placed on the surface, whereas the loss in viability became less with increased depth of burial. Possible explanations for this adaptation of enhanced survival when buried are discussed.

Comparing responses of grain legumes, wheat and canola to applications of superphosphate

Abstract: Phosphorus (P) is a major deficiency of soils of south-western Australia (WA) The fertilizer P requirements are not known for grain legumes being evaluated for neutral to alkaline, fine textured soils in WA To rectify this, glasshouse and field experiments were undertaken to compare the responses of several grain legume species, wheat and canola to applications of single superphosphate and the results are reported in this paper The glasshouse experiments measured responses of dried tops, harvested at 26 to 42 days after sowing, to P that was freshly-applied (current P) and previously-applied (previous P) Responses in the glasshouse were measured using yield, P concentration and P content (P concentration multiplied by yield) of oven dried tops of the following: wheat (Triticum aestivum), canola (Brassica napus), faba bean (Vicia faba), chickpea (Cicer arietinum), lentil (Lens culinaris), field pea (Pisum sativum), albus lupin (Lupinus albus) and narrow leaf lupin (Lupinus angustifolius) Field experiments in 1994 and 1995 compared seed (grain) yield responses of faba bean, chickpea, lentil, albus lupin and wheat to applications of current P The P was banded (drilled) with the seed while sowing at 5 cm depth Canola and wheat produced very large yield responses to increasing applications of current P Responses were much smaller for albus lupin, faba bean and chickpea Responses for lentil, narrow leaf lupin and field pea, fell in between responses of the small and large seeded species Similar trends for responses were obtained as measured using yield, P concentration, or P content For soils treated with previous P, similar trends were observed as for current P, but differences in yield responses between species were much less marked and the response curves tended to become more sigmoid In the field experiments, grain yield responses to current P of albus lupin and chickpea were less than that for wheat Relative to wheat, faba bean was the most responsive grain legume to applications of current P, with lentil producing similar responses to wheat in one experiment at a newly cleared, P deficient site

Hessian Fly (Diptera: Cecidomyiidae) Injury and Loss of Winter Wheat Grain Yield and Quality

Abstract: The damage–yield-loss relationships of Hessian fly, Mayetiola destructor Say, in soft red winter wheat, Triticum aestivum L., were examined using results of studies on Hessian fly management and yield loss that were conducted over a 9-yr period with various cultivars and planting times and at various locations in Georgia. Differences in grain yield and test weight of susceptible and resistant cultivars with or without a systemic insecticide (disulfoton or phorate) at planting were compared with the percentage of infested tillers in autumn (vegetative stage) and the percentage of infested stems or the number of immatures per stem in spring during grain filling. Grain yield loss increased linearly with increasing percentage of autumn-infested tillers and spring-infested stems. Infestations had little effect on grain test weight until infestations exceeded 20% of autumn-infested tillers or 38% of spring-infested stems. Grain yield and test weight losses were exponentially related to number of immatures per stem during grain filling, with proportionate loss increasing as immature numbers increased up to 6 immatures per stem. Analysis of grain yield components of headed stems found that injury reduced seeds per spike, spikelets per spike, seeds per spikelet, and seed weight. Gain thresholds indicated that, depending on commodity price, an application of a systemic insecticide at planting provided positive marginal returns for 68–74% of plot-years ( n = 50) on susceptible cultivars but only provided positive returns for 23–27% of plot-years ( n = 26) on resistant cultivars. Depending on control cost, economic damage occurred when autumn infestations exceeded 5–8% of infested tillers or when spring infestations exceeded 13–20% of infested stems, or 0.4–1.0 immatures per stem. These results provide a quantitative basis for Hessian fly damage loss assessment in wheat.

Smoke affects the Germination of Native Grasses of New South Wales

Abstract: The germination responses to plant-derived smoke of seeds of 20 native grass species from New South Wales, Australia, were tested under laboratory conditions. The species belonged to 14 genera including Bothriochloa, Chloris, Cymbopogon, Danthonia, Dichanthium, Digitaria, Eragrostis, Eriochloa, Microlaena, Panicum, Paspalidium, Poa, Stipa and Themeda. The interaction between smoke and husk-imposed dormancy was examined by removing the floral structures surrounding the seeds, when sufficient seeds were available. Smoke was shown to be an important environmental stimulus for breaking the dormancy of native grasses; however, the response differed considerably between different genera and between species of the same genus. For almost half of the species, smoke significantly increased the germination percentage. Panicum decompositum showed the greatest response, with germination increasing from 7.7 to 63.1% when smoke was applied. Panicum effusum had no germination in the absence of smoke, but 16.7% germination when smoke was applied. Stipa scabra subsp. scabra had germination significantly reduced by smoke from 30.2 to 19.9%. Five species had their germination rate, but not the final germination percentage, affected by smoke, and a third of the species were unaffected by smoke. For five of the species, Chloris ventricosa, Dichanthium sericeum, Panicum decompositum, Poa labillardieri and Stipa scabra subsp. falcata, this is the first report of a smoke-stimulated germination response. For those species with germination promoted by smoke, retention of the covering structures did not prevent smoke stimulation of germination. Sowing smoke-treated husked seeds is likely to be preferable as it would still promote greater germination, whereas dehusking seeds can result in the seeds being more susceptible to desiccation and fungal attack in the field. It is suggested that other grassland communities that respond to pyric conditions may also contain species that respond to smoke.

A Comparison of Winter Cereal Species and Planting Dates as Residue Cover for Cotton Grown with Conservation Tillage

Abstract: Winter cereals are often used as cover crops before planting cotton (Gossypium hirsutum L.). Black oat (Avena strigosa Schreb.) is the predominate cereal cover crop for cash crops in southern Brazil and Paraguay, but limited information is available on the suitability of black oat as a cover crop in the southeastern USA. The objectives of this study were to compare black oat with adapted winter cereals for this region and to determine the effect of cereal residue species and amount on cotton growth, N status, and lint yield. In a greenhouse study in which black oat and rye (Secale cereale L.) residues were mixed with soil, tap root elongation of both cotton and radish (Raphanus sativa L.) was inhibited more by black oat residue than by rye residue. In a field experiment on a Goldsboro loamy sand (fine-loamy, siliceous, thermic Aquic Kandiudult), cotton was grown in 1995 and 1996 following black oat, oat (Avena sativa L.), rye, and wheat (Triticum aestivum L.) that were planted at three different times (October, November, and December). AH four winter cereals had similar hiomass production at each planting date in 1995. In 1996, rye was the only species not visibly damaged by a low temperature of -12.2°C that occurred during the winter. Black oat biomass was comparable to wheat in all planting dates but averaged 60% less than rye over all three planting dates and was 37% less than oat in the October planting date in that year. Black oat tended to have a higher N concentration than the other cereal species. Cotton plant density was lowest following black oat and rye. Cotton growth, leaf blade N, and petiole NO 3 -N were more dependent on residue amount than on residue species. Cotton lint yield following black oat was 120 kg ha -1 higher than lint yield of cotton following rye. Cotton following black oat, wheat, and oat had similar lint yield. Black oat may be a promising cover crop for the southeastern USA, but evaluations of other cultivars and/or improvement programs to improve cold hardiness are needed to improve the utility of this species.

Kinetics of dormancy release and the high temperature germination response in Aesculus hippocastanum seeds

Abstract: The kinetics of primary dormancy loss were investigated in seeds of horse chestnut (Aesculus hippo-castanum L.) harvested in four different years. Freshly collected seeds from 1991 held for up to 1 year at temperatures between 2 degrees C and 42 degrees C exhibited two peaks in germination (radicle growth), representing a low temperature (2-8 degrees C) and a high temperature response (31-36 degrees C), Germination at 36 degrees C generally occurred within 1 month of sowing, but was never fully expressed in the seedlots investigated. At low temperatures (2-8 degrees C), germination started after around 4 months. Generally, very low levels of germination were observed at intermediate temperatures (11-26 degrees C). Stratification at 6 degrees C prior to germination at warmer temperatures increased the proportion of seeds that germinated, and the rate of germination for all seedlots. Within a harvest, germination percentage (on a probit scale) increased linearly with stratification time and this relationship was independent of germination temperature (16-36 degrees C), However, inter-seasonal differences in the increases in germination capacity following chilling were observed, varying from 0.044 to 0.07 probits d(-1) of chilling at 6 degrees C, Increased sensitivity to chilling was associated with warmer temperatures during the period of seed filling. The estimated base temperature for germination, T-b for newly harvested seeds varied slightly between collection years, but was close to 25 degrees C. For all seedlots, T-b decreased by 1 degrees C every 6 d of chilling at 6 degrees C. This systematic reduction in T-b with chilling ultimately facilitated germination at 6 degrees C after dormancy release.

Enhancement of botanical diversity of permanent grassland and impact on hay production in Environmentally Sensitive Areas in the UK

Abstract: Five methods for increasing the botanical diversity of permanent grassland, either by sowing site-specific species-rich grass/forb seed mixtures (strip-seeding; or over-sowing after sward disturbance by light harrowing, partial rotary cultivation or turf removal), or by introducing transplanted plug plants, were compared with a control treatment in replicated field experiments on six farm sites in Environmentally Sensitive Areas (ESAs) in England and Wales. Effects on herbage production under hay cutting in July and on botanical composition were recorded in the two subsequent years. Turf removal before sowing was the only treatment that significantly reduced herbage production; this treatment also had the greatest effect on increasing botanical diversity (to a mean of twenty-eight plant species per site compared with fifteen species for the control 2 years after sowing). The least successful establishment of sown species resulted from light harrowing before sowing; the rotary-cultivated and strip-seeded treatments increased species diversity, although by less than turf removal. Successful establishment of introduced species was greatest on sites having a low soil nutrient status. Species that established successfully from seed on most sites and treatments included the grasses Alopecurus pratensis, Cynosurus cristatus, Festuca rubra and Phleum pratense, and the forbs Achillea millefolium, Leucanthemum vulgare, Plantago lanceolata and Prunella vulgaris; in addition, Centaurea nigra, Hypochoeris radicata and Lotus corniculatus were also established by one or more methods on most sites. Lychnis flos-cuculi established successfully on mesotrophic sites, and Medicago lupulina on calcareous sites. Several species failed to establish at all or most sites where they were sown, e.g. Helianthemum nummularium, Pimpinella saxifraga and Rhinanthus minor. Most transplanted plug-plant species established successfully in the short term, but many failed to persist or their frequency in the sward remained low; exceptions included A. millefolium and P. lanceolata. The results are discussed in relation to the requirements for management to further the objectives of ESAs and agri-environmental schemes.

Response of Chickpea to Seed Priming in the High Barind Tract of Bangladesh

Abstract: In on-farm field trials at 30 locations in the Ataher, Amnura and Nachole soil series area of the High Barind Tract, Cicer arietinum cv. Barichola-2 seeds were primed (soaked in water overnight and then surface dried) or not primed before sowing at 50 kg seed/ha. Seed priming increased seedling emergence, plant height, number of pods/m², 1000-seed weight, grain yield and residue yield by 21, 22, 39, 6, 47 and 31%, respectively, and decreased the number of diseased plants/m², pod borer (Helicoverpa armigera) damaged pods/m² and number of unfilled pods/m² by 45, 13 and 21%, respectively.

Studies on Sowing Depth for Chickpea (Cicer arietinum L.), Faba Bean (Vicia faba L.) and Lentil (Lens culinaris Medik) in a Mediterranean-type Environment of South-western Australia

Abstract: Pulses such as chickpea, faba bean and lentil have hypogeal emergence and their cotyledons remain where the seed is sown, while only the shoot emerges from the soil surface. The effect of three sowing depths (2.5, 5 and 10 cm) on the growth and yield of these pulses was studied at three locations across three seasons in the cropping regions of south-western Australia, with a Mediterranean-type environment. There was no effect of sowing depth on crop phenology, modulation or dry matter production for any species. Mean seed yields across sites ranged from 810 to 2073 kg ha -1 for chickpea, 817-3381 kg ha -1 for faba bean, and 1173 2024 kg ha -1 for lentil. In general, deep sowing did not reduce seed yields. and in some instances, seed yield was greater at the deeper sowings for chickpea and faba bean. We conclude that the optimum sowing depth for chickpea and faba bean is 5 8 cm, and for lentil 4-6 cm. Sowing at depth may also improve crop establishment where moisture from summer and autumn rainfall is stored in the subsoil below 5 cm, by reducing damage from herbicides applied immediately before or after sowing, and by improving the survival of Rhizobium inoculated on the seed due to more favourable soil conditions at depth.