Showing papers in "Agronomy Journal in 1985"

Row Spacing, Plant Population, and Water Management Effects on Corn in the Atlantic Coastal Plain

Abstract: Lack of water because of erratic rainfall frequently limits corn (L.) production on Typic Paleudults in the Atlantic Coastal Plain. Traditionally, wide (96 cm) row spacing and low plant population have been used to prevent water stress, but recently landowners have begun to invest in irrigation systems. Changes in row spacing, plant population, or fertilization practices may be required to achieve maximum water-and nutrient-use efficiency with those systems. We evaluated plant population treatments averaging 7.0 and 10.1 plants m in single and twin rows on a Norfolk (fineloamy, siliceous, thermic Typic Paleudult) loamy sand during 1980, 1981, and 1982. Three water management [nonirrigated, irrigated using tensiometers (TENS) to measure soil-water potential for scheduling, and irrigated using a computer-based water balance (CBWB) for scheduling], and two fertilization programs were also evaluated in a four-factor split-plot design. Water management and plant population interacted significantly. Planting in twin rows increased grain yield an average of 0.64 Mg ha (l0 bu/A), but planting more than 7.1 plants m significantly increased grain yield only in 1980. Irrigation increased grain yield 150, 161, and 8% in 1980, 1981, and 1982, respectively, as a result of increased kernel weight and number of kernels per ear. Increasing total N, P, and K application beyond 200, 30, and 167 kg ha-’, respectively, did not significantly influence grain yield or yield components. Yield advantages of narrow rows can be obtained on Coastal Plain soils which require subsoiling by using a twin-row planting configuration. Irrigation can be scheduled using either tensiometers (soil-water potential) or a computerized water balance without significantly changing corn grain yield, nutrient accumulation, or yield components.

Nitrogen Requirements of Potatoes

Abstract: Nitrogen fertilizer applications, for maximum fertilizer efficiencies and crop yields, should be based on the N required by the crop during its various growth stages. The objectives of this paper were to identify the N requirements of the potato plant (Solanum tuberosum L.) during growth and to evaluate selected soil and plant tissue tests as indicators of the plant's N status. Growth analysis data and soil and petiole NO3-N concentrations were obtained at predetermined time intervals from N fertilization treatments in replicated field studies on a coarse-silty mixed, mesic Durixerollic Calciorthrid soil. Maximum early tuber growth occurred when leaf area index was between 2.5 and 3.2 and the tops contained between 79 and 100 kg N ha-1 at the start of linear tuber growth. A preplant N fertilizer application between 67 and 134 kg ha-1 gave these characteristics under the experimental conditions. The maximum dry matter production rate per day (approx. 250 kg ha-1) occurred when there was between 80 and 140 kg N ha-1 in the plant tops and roots. An average tuber growth rate of 0.75 Mg ha-1 day-1 required a N uptake rate of 3.7 kg ha-1 day-1 to prevent the loss of N and dry matter from the tops and roots. Sufficient N was available for this rate when the soil NO3-N concentration was > 7.5 mg kg-1 (0.46-m soil depth), corresponding to 15 000 mg kg-1 NO3-N in the fourth petiole. Soil and petiole NO3-N concentrations may be used to adjust the N fertilization rates during the growing season. This practice has the potential of increasing the overall N fertilizer use efficiency and final tuber yields within the climatic, disease, and variety limitations.

Heritability of NaCl Tolerance in Germinating Alfalfa Seeds

Abstract: A major limitation to crop production throughout much of the world is soil salinity, which is increased by irrigation and fertilization. One way to better utilize saline soils is to grow salt tolerant crops. The objective of this research was the development of salt tolerance in germinating alfalfa (Medicago sativa L.) seeds. Five cycles of mass selection for NaCl tolerance during seed germination were conducted in the cv. Mesa-Sirsa. Standard germination techniques were employed using blotter paper saturated with NaCl solutions of five different concentrations at a temperature of 26° C. The osmotic potential of the NaCl solution needed to produce 1% seed germination decreased from −1.40 to −2.45 MPa during the five cycles of selection. Germination at −1.30 MPa osmotic potential increased from 3% for the source population to 86% for the fifth cycle of selection. The broad sense heritability estimate for NaCl tolerance during seed germination, averaged over all cycles of selection and five levels of osmotic potential, was 50%. Significant progress was made in the development of salt tolerance in germinating alfalfa.

Root Damage by Western Corn Rootworm and Nutrient Content in Maize

Abstract: Little is known about the effects of root pruning by insects on nutrient content of maize (Zea mays L.). The objective of this study was to evaluate root damage effects caused by western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) larval feeding on Fe, Na, K, Ca, Mg, and N contents in shoots and seeds of maize hybrid ‘Pioneer 3978’. The experimental design was a randomized complete block, and treatments included applications of 0, 1000, 2000,4000, and 8,000 WCR eggs per lineal meter of row in 1982 and 0,4000, and 12 000 WCR eggs per lineal meter of row in 1983. Maize seeds were planted ca. 23 cm apart in Brookings sic1 (pachic Udic Haploborolls) soil. Aboveground plant samples were collected before intense larval feeding and after adult beetle emergence. These shoot samples and grain harvested at maturity were weighed and analyzed for their nutrient content. Severe root pruning decreased shoot dry weight and reduced grain yields at harvest by 13.5% in 1982 and by 9.7% in 1983. Contents of K, Mg, and Ca decreased and Fe and Na contents increased in shoots in 1982, but were not affected by root pruning in 1983. Accumulation of Na and Fe in shoots was attributed to compensatory branch root growth at critical stages of plant development. Root pruning may have caused new root development or branching into parts of the soil where Fe and Na could be obtained. Grain yield and grain Na content were related directly to the amount of root pruning in 1982. In 1983, grain yield was reduced and element content was altered by root pruning, but not in a simple linear manner. The results suggested that further studies of root pruning by WCR larvae of additional hybrids and their inbred parents may aid identification of elemental functions for maize.

Nitrogen utilization of corn under minimal tillage and moldboard plow tillage. I. Four-year results using labeled N fertilizer on an Atlantic coastal plain soil

Abstract: Crop responses and N uptake of corn (Zea mays L.) grown with moldboard plow tillage (PT) and minimal tillage (MT) were measured in a 4-yr field experiment on a Mattapex silt loam soil (finesilty, mixed, mesic, Aquic Hapludult) near Salisbury, MD (Atlantic Coastal Plain region). Labeled ammonium sulfate or ammonium nitrate (¹⁵N depleted) was applied annually to the entire area (74 m²) of each plot at five N rates ranging from 0 to 180 or 270 kg N ha⁻¹. Corn dry matter yield, N content, and isotope composition were determined in the entire plant at the 11 to 12 leaf stage and at silage harvest, as well as in the corn grain at maturity. Below 135 kg N ha⁻¹, dry matter yields, total N uptake, and fertilizer N (FN) uptake were greater with PT than with MT, but with 180 kg N ha1⁻¹ there was either no difference between the tillage systems or MT was greater than PT. Fertilizer N additions had no consistent or practically significant effect on soil N (SN) uptake. At 13S kg N ha⁻¹, average crop FN recoveries were 62% for PT and 53% for MT, but this difference decreased with increasing N rate until both tillage systems averaged about 53% recovery at 180 kg N ha⁻¹. Average SN uptake was greater with PT culture than with MT culture, averaging 76 kg N ha⁻¹ and 59 kg N ha⁻¹, respectively. The crop N requirement of corn was about 17 kg N ha⁻¹ greater for MT corn than PT corn due to a 10% greater yield of total dry matter with MT. Corn grown with MT required about 68 kg more FN ha⁻¹ than PT, due to a lower uptake of SN and a greater crop N requirement. A lower uptake of N on MT plots during the second half of the growing season suggests (i) a greater net mineralization of N on PT plots and/or (ii) a greater loss of N via leaching and/or denitrification on MT plots. A nitrogen concentration of about 11 to 12 mg N g⁻¹ in the silage total dry matter, or about 15 mg N g⁻¹ in the grain, can be used as an approximate value for N sufficiency. However, these values should be considered broad guidelines since significant deviations were observed in individual years.

Effect of Water Deficit at Different Growth Phases of Peanut. I. Yield Responses

Abstract: Response of groundnut cv. Robut 33-1 to drought stress imposed at (a) emergence to maturity, (b) emergence to peg initiation, (c) from the start of flowering to the start of seed growth, and (d) from the start of seed growth to maturity was studied during the post-rainy seasons of 1980-81 and 1981-82. The amount of water applied during these phases was varied using line-source irrigation, but the crops otherwise were irrigated uniformly at regular intervals. The greatest reduction in seed yield (28-96%) occurred when stress was imposed during (d). Decreased irrigation during (b) increased pod yield relative to the fully irrigated control treatment by 19% in 1980-81 and 13% in 1981-82. The evapotranspiration-yield relationships showed a strong interaction with timing of drought

Phosphorus Efficiency and Phosphate-Iron Interaction in Maize

Abstract: Genotypic differences in absorption or utilization of P might be exploited to improve efficiency of fertiliir use or to obtain higher productivity on P-deficient soils. Experiments were conducted to determine rates of P absorption, P accumulation, and P utilization in 15 inbred genotypes of maize (Zea mays L.) at 3 P supply levels. Nutrient solution P concentrations were maintained at approximately 5,25, and 100 mmol m⁻³ (Pl, F‘2, and P3, respectively) with an alumina-P solid phase buffer. There were significant differences among genotypes for rate of P utilization, but not for rate of P absorption by roots. Utilization of P was negatively correlated with the ratio of inorganic P accumulation rate to total P accumulation rate, indicating that P utilization is limited by partitioning of P between free orthophosphate and organically combined forms. Absorption of P by roots and utilization of P in shoots were positively correlated. Iron deficiency occurred with all genotypes grown in the P2 and P3 treatments, but not in the P1 treatment. Both Fe absorption by roots and partitioning of Fe to shoots decreased with increasing concentration of P in the nutrient solution. Utiliition of Fe (rate of dry matter production per unit of Fe accumulated) in shoots increased in Fe-deficient plants. Phosphate-induced Fe deficiency in maize evidently involves both inhibition of Fe absorption by roots and inhibition of Fe transDort from roots to shoots.

Row spacing and seeding rate effects on yield and yield components of soft red winter wheat

Abstract: Information to determine optimum row spacing and seeding rates for soft red winter wheat (Triticum aestivum L. em Thell.) in highyielding environments in the mid-Atlantic Coastal Plain region is not available. Three field experiments were conducted in the Coastal Plain of Virginia (on Typic Hapludult and Aquic Quartzipsamments soils) to evaluate row spacing and seeding rate influences on grain yield of winter wheat grown with intensive management. Seeding rates ranging from 186 to 558 seeds m⁻² were studied in row spacings of 10 and 20 cm with additional treatments of 744 and 1116 seeds m⁻² in 10-cm row spacings. Intensive management included adequate supplies of P, K, and micronutrients as preplant fertilizer, insecticide, and fungicide use, and split-spring N applications. Measurements included wheat grain yield and yield components. Ten-centimeter row spacings produced 0.6 to 0.8 Mg ha⁻¹ higher grain yields than 20-cm row spacings at similar seeding rates. Yield levels ranged from 5.0 to 8.1 Mg ha⁻¹. Heads m⁻² and kernels head⁻¹ varied with seeding rate to a greater extent than weight kernel⁻¹. Yields did not vary over a wide range of plant populations, but were reduced with low (469 heads m⁻²) or high (897 heads m⁻²) harvest populations. Seeding rates of 372 to 744 seeds⁻² in 10-cm rows were sufficient to produce high yields with the ‘Tyler’ cv. grown under intensive management.

Effects of salinity on seashore paspalum turfgrasses

Abstract: Etude de la croissance de quatre selections de Paspalum vaginatum, cultives dans des solutions nutritives de differentes salinites

Influence of Tillage on Nutrient Uptake and Yield of Corn1

Abstract: Though it appears that the surface accumulation of soil nutrients and the shallower distribution of roots is not detrimental to crop growth and yield under no-tillage management, supportive data with respect to nutrient uptake are scarce. A field plot study was conducted over 3 yr utilizing four tillage treatments: (i) conventional tillage (moldboard plow); (ii) no-tillage (coulter); (iii) no-tillage with shallow (10 to 15 cm) in-row chisel; and (iv) no-tillage with deep (30 to 45 cm) in-row chisel. The objective was to determine the influence of tillage on nutrient uptake and yield of corn by: (i) measuring changes in distribution of soil nutrients; (ii) determining the nutrient status of corn plants; (iii) measuring rubidium (Rb) uptake by corn plants when Rb was placed at various row positions and depths in the soil profile; and (iv) measuring grain yields. No-tillage treatments resulted in a redistribution and concentration of soil nutrients at the soil surface, compared with conventional tillage. However, the nutrient status of plants grown under no-tillage management was equal or superior to those grown by conventional tillage. Furthermore, the activity of roots and the extraction of water and nutrients, as evidenced by Rb uptake, was greater for no-tillage compared with conventional tillage. No-tillage, whether in-row chisel was included or not, resulted in larger plants and greater grain yields. No evidence was obtained that would support deeper placement of nutrients or in-row chisel operations to improve subsoil rooting under no-tillage.

Mycorrhizal Colonization of Crested Wheatgrass as Influenced by Grazing1

Abstract: On evalue l'effet de la charge en betail sur la colonisation mycorrhizienne vesiculo-arbusculaire d'une graminee introduite dans les terrains de parcours du Nevada central

Soybean Irrigation Serially Timed During Stages R1 to R6. II. Yield Component Responses1

Abstract: Soybean [Glycine max (L.) Merr.] seed yield components are established and fixed in a temporally ordered sequence during stages R1 to R6. To determine the effect of irrigation timing during R1 to R6 on these traits, we examined the seed yield component responses of 16 soybean cultivars to nine irrigation treatments in a 3-year experiment. Treatments T₁ thru T₇ consisted of only a single irrigation coinciding with the average R stages 1.1, 2.5, 3.7, 4.7, 5.6, 5.9, and 6.4, respectively. ‘Check’ treatments included TO, which was not irrigated, and T₈ which received seven total irrigations coincident with those for T₀ and T₇. Averaged over cultivars and years, the mean number of seeds/plant were: T₀: 87f, T₁: 121a, T₂: lllbc, T₃: 115ab, T₄: 105cd, T₅: 99def, T₆: 102de, T₇: 95ef, and T₈: 122a. T₀ and T₈ thus established the minimum and maximum ‘limits’ in the seeds/plant response, respectively, with declining responses as irrigation was delayed from T₁ to T₇. The 100-seed weight (9) means were: T₀: 19.lb, T₁: 17.8c, T₂: 17.8c, T₃: 18.3c, T₄: 20.3a, T₅: 20.4a, T₆: 19.8ab, T₇: 20.3a, and T₈: 18.3c. Seed size for T₈ was thus smaller than T₀. The T₄ thru T₇ responses were significantly greater than T₀, while the T₁ thru T₃ responses were significantly less than T₀. Average seed yields were greatest for the T₃ and T₄ treatments, although for determinate cultivars, T₈ also resulted in high yields. Only minimal changes in seed number and size were affected by irrigation in the determinate cultivars (in contrast to indeterminates), which may have accounted for the greater yield responsiveness of determinate cultivars to irrigation. Based on both the seed yield and yield component data, it would appear that stage R3.5 to R4.5 represents the reproductive period in soybeans most responsive to irrigation.

Linear Increase in Soybean Harvest Index during Seed‐Filling1

Abstract: Grain-to-stover ratio and harvest index (the ratio of seed mass to total aboveground mass) were studied during soybean [Glycine max (L.) Merr.] seed-filling to determine the potential for using these normalized expressions of yield to improve measurements of the seed-filling period. For example, if either grain-to-stover ratio or harvest index increased linearly during seed-filling, it could be used to calculate an effective filling period. However, calculation of an effective filling period requires a linear approximation. Thus, the specific objective was to determine whether grain-to-stover ratio or harvest index increased as a linear function of time for various genotypes and environments. First, C and N assimilation and distribution rates within plants were simulated. Simulations predicted that harvest index increased linearly throughout seed filling, while grain-tostover ratio increased curvilinearly. Next, simulations were compared with data from field-grown plants at three northern locations. Cultivars included determinate and indeterminate types, and a range from early to late maturities. To a good approximation, harvest index increased linearly during the seed-filling period for all but the early cultivars. The early cultivars approached maximum values of harvest index curvilinearly. Therefore, harvest index has potential for use in calculations which require linear approximations.