Sowing

About: Sowing is a research topic. Over the lifetime, 33888 publications have been published within this topic receiving 273438 citations. The topic is also known as: seeding.

Effects of bryophytes and grass litter on seedling emergence vary by vertical seed position and seed size

Abstract: Establishment of plants through seeds is often constrained by the quality of microsites, which is in part controlled by the nature and amount of ground cover. The latter consists of living shoots of vascular plants or bryophytes and/or the dead remains of the dominant species. In the present article, we report the results of a controlled pot experiment with five species characteristic of floodplain grasslands. We manipulated the amounts of grass litter and/or mosses to study (1) differences between ground cover types with respect to their effects on microenvironment and seedling emergence and (2) how these effects interact with seed size and seed sowing position. Increasing amounts of both cover types led to increasing soil humidity, whereas temperature amplitude and illumination were decreased. However, since grass litter decomposed much faster than bryophytes, light conditions for germination under grass litter improved considerably with time. Although seedling emergence varied significantly between species, ground cover types and cover amounts, seed position alone explained about 50% of the variation in the data set. Additionally, we found an important interaction between seed size, seed position and cover type: large-seeded species showed a fitness advantage when seeds were situated beneath a cover, irrespective of cover type, which disappeared when seeds were shed on top of a cover layer. We suggest that this interaction may be ecologically and evolutionarily relevant because it may lead to changes in species composition and diversity of plant communities as a consequence of changes in the amount and type of ground cover.

Effects of conventional tillage and no tillage permutations on extracellular soil enzyme activities and microbial biomass under rice cultivation

Abstract: Extracellular soil enzymes hold a cardinal position in nutrient dynamics by regulating bioavailability of elements, and hence are linked with soil health. The present study aimed to analyze the responses of extracellular enzymes involved in mineralization of carbon (β-d-glucosidase (BG), cellobiohydrolase (CBH), polyphenol oxidase (PPO)), nitrogen (urease (UR), glycine-amino peptidase (GAP)) and phosphorous (alkaline phosphatase (ALP)) under four permutations of conventional tillage and no tillage under rice–wheat system in eastern Indo-gangetic plains during rice cultivation period. The permutations were: tillage before sowing/transplantation of each crop (RCT–WCT), tillage before transplantation of rice and no tillage before sowing of wheat (RCT–WNT), tillage before sowing wheat and no tillage before sowing of rice (RNT–WCT) and no tillage before sowing of each crop (RNT–WNT). Microbial biomass carbon and nitrogen and activities of BG, CBH, ALP and UR increased with reduction in tillage frequency, becoming the highest under RNT–WNT and the lowest under RCT–WCT. Principal component analyses (PCA) condensed the variables in to two components, apparently described by soil temperature and moisture content under all the tillage permutations. Most of the enzymes and soil properties identified to be associated under PCA followed linear relationships. Under RCT–WCT, CBH, UR and ALP were related with BG. Different orders of residue incorporation and tillage under RCT–WNT, RNT–WCT and RNT–WNT masked these relations. Results indicated that reduction in tillage frequency made the soil healthier. Relationship of BG with other enzymes appeared as a probable indicator to reflect deviations from the conventional cultivation practice in the study region.

Evaluating physicochemical constraints of Calcarosols on wheat yield in the Victorian southern Mallee

Abstract: Soil salinity, sodicity, and high extractable boron (B) are thought to reduce wheat yields on alkaline soils of south-eastern Australia; however, little quantitative information on yield penalties to edaphic constraints is available. The relationships between wheat yield of a B-tolerant cultivar and soil physicochemical conditions in the Victorian Mallee were explored using ridge regression analysis, using natural variation in the field. Wheat yields in the survey ranged from 1.3 to 6.1 Mg/ha, with low yields attributed to inadequate soil water supply during pre-anthesis growth. Crop sequences, fallow–wheat, and pulse–wheat left greatest soil water prior to sowing of the wheat crop, and lucerne–wheat the least. A descriptive model explained 54% of variation in wheat yield, with rainfall around anthesis, available soil water in the 0.10–0.40 m layer, nitrate in the 0–0.10 m layer at sowing and salinity, and sodicity in the 0.60–1.00 m layers being important factors. Subsoil salinity (ECe) and sodicity (ESP) appear to be effective surrogates for estimating the likelihood of water extraction in the deep subsoil. The analyses suggest that subsoils need to have an ECe <8 dS/m and ESP < 19% for crops to make use of water deep in the profile. Although soluble B ranged from 2 to 52 mg/kg in the 0.60–1.00 m layer of the alkaline soils considered, B appeared to have little correlation with root growth, water extraction, or yield of wheat, which has been attributed to B-tolerance of the cultivar tested and/or the overbearing effect of high Na+ in these soils.

Growth of shoots and roots, and interception of radiation by wheat and lupin crops on a shallow, duplex soil in response to time of sowing

Abstract: Crops of lupin (Lupinus angustifolius L cv Gungurru) and wheat (Triticum aestivum cv Kulin or Spear) sown close to the break of the season and 3-6 weeks later were grown on a duplex soil at East Beverley, WA, over 3 seasons The overall aim of the work was to examine the influence of time of sowing on growth and water use of the crops, and this paper reports their growth and yield Early sowing resulted in greater shoot weight of all crops (up to 28 t/ha for lupin and 17 t/ha for wheat at maturity) and grain yield of lupin, but grain yield of wheat was increased in only 1 of the 3 seasons The principal effect of the delayed sowing was to reduce the duration of linear growth; the rate of the initial exponential phase was slightly reduced by later sowing as was the rate of growth during the linear phase in lupin (by about 15 g/m2day) but not in wheat Late sowing generally reduced both the number of pod/ears per unit area and the number of grains per pod/ear Doubling the density of sowing in one of the seasons had no effects on the shoot weight and grain yield of lupin with early or late sowing but decreased those of wheat Downward root growth of early-sown crops averaged 52 mm/day for lupin and 87 mm/day for wheat in the 3 seasons and ceased at about 08 m; time of sowing had no effect on these measures Root weight at flowering was greater in lupin than in wheat crops, and root weight of lupin was about 05 of total plant weight during vegetative growth compared with 025-03 in wheat Typically, only 5-6% of the root length of both crop species was present in the clay layer at flowering irrespective of sowing time The proportion of radiation intercepted reached a higher maximum value for early-sown crops (about 075 in 1991 and 090 in 1992) than late-sown crops (about 060 in 1991 and 08 in 1992) The conversion coefficients of radiation to dry matter were very similar (about 18 g/MJ) for both species, but the greater partitioning of dry matter to roots in lupin than wheat meant that conversion coefficients for shoot dry matter were greater in wheat (143-168 g/MJ) than in lupin (093-116 g/MJ) The results demonstrate that early sowing produced larger crops of both lupin and wheat; this resulted in larger lupin yields, but yield of wheat was affected by disease and drought during grain filling