Nitrogen efficiency of grain sorghum grown on flat and raised seedbeds on poorly drained soil

Grain sorghum (Sorghum bicolor L. Moench) production commonly occurs on poorly drained clayey soils of the Mississippi River delta region inArkansas. Raised, wide seedbeds may improve grain yield and fertilizer N efficiency for narrow‐row sorghum production on these soils. The influence of individual row positions on raised, wide seedbeds was compared to conventional flat seedbed for grain yield, yield components, dry weight, and N uptake. A 193‐cm wide and 15 cm high crowned seedbed (CB) was compared to the flat seedbed (FB) in 1987 and 1988 on a Sharkey silty clay (very fine, mont‐morillonitic, nonacid, thermic, Vertic Haplaquepts) at Keiser, AR. Three rows were planted on each seedbed treatment; one in the middle of the bed and one row 48 cm to each side of the row in the middle. Nitrogen rates of 0, 56, 112, and 168 kg/ha were applied at planting. In addition, two split applications at the 168 kg/ha N rate (56 kg N/ha at planting and 112 kg N/ha at either four‐leaf or eight‐leaf growth stage) were evaluated. Each row position was evaluated for grain yield, yield components, plant dry weight, and N uptake. Whole plant samples were collected at the anthesis and physiological maturity growth stages. The field average grain yield was higher on the CB each year regardless of N rate applied at planting. This yield increase on the CB was related to the row on the top of the CB yielding more than the equivalent row on the FB. The responses of plant dry weight at each growth stage, N uptake at each growth stage, and N content of the seed was similar to grain yield responses. The split N application at planting and the eight‐leaf growth stage was as effective or better than any other treatment for increasing grain yield, N uptake, and seed N content.     

Nitrogen rates in strawberry (Fragaria ananasa) nursery on growth and yield in the field

Strawberry (Fragaria ananassa cv. Aliso) plants were grown under three N‐rates in the nursery: 80, 320 and 640 kg N/ha, and then transplanted to the fruiting field. Plants from each nursery treatment were given 150, 300 and 450 kg N/ha. The fertilizer was given as ammonium sulfate in the nursery and as ammonium nitrate in the field, a part broadcasted before planting and the other part applied as top dressings. Biomass production, plantlets size distribution and N content were restricted by the lowest level of N given in the nursery. Plants grown at 320 kg N/ha in the nursery gave significantly earlier and higher total yields than those grown at the other rates. Fruit yields were not significantly influenced by the N‐application in the field. N fertilization in the early stages of strawberry plant development in the nursery is more important than later field application.

The influence of N fertilization on the growth and yield of strawberry plants has been studied by several workers. In some reports yields were increased when the rate of N applied was increased (1, 2, 3). In other studies no influence was found (4, 5, 6), or even a decrease in yield was reported as the rate of applied N was increased (7). While in some studies detrimental effects of N‐fertilizer on fruit yield were observed at 200–300 kg N/ha (8, 9), in other studies (6, 7) N applications up to 400 kg/ha did not affect yield. In Spain (3), adding up to 680 kg/ha caused an increase in fruit yield.

Even at relatively low applied‐N levels, up to 150 kg N/ha, strawberry response reports are not consistent. Some workers found that increasing N in this range caused an increase in fruit yield (8, 9, 3, 7, 10), while no effect was observed (4, 5, 6, 11) in several other studies. Most of the reported experiments with N‐fertilizer were carried out after plants were transplanted from the nursery to the field. To the best of our knowledge no attempt was made to evaluate the effect of fertilizer applied in the nursery.

The objective of this work was to evaluate the influence of different levels of N‐fertilizer, in both the nursery and the field, on strawberry plant development and composition, earliness, yield level and yield distribution.     

Role of continuous nitrogen fertilization on nutrient composition of leaves sampled at various stages of growth and on yield of yam (Dioscorea rotundata)

Abstract

White yam (Dioscorea rotundata cv. Olonko) was grown consecutively for three growing seasons, i.e. from February to October of 1975, 1976 and 1977, and treated with six levels of nitrogen, viz: 0, 40, 60, 120, 160 and 200 kg N/ha in the field. Leaf samples were taken at four stages of growth as follows: vegetative, tuber formation, tuber development and tuber maturation, and analyzed for NO₃‐N, P, K, Ca and Mg.

Increasing nitrogen fertilization consistently increased leaf‐NO₃‐N, particularly at the vegetative stages of growth, while no consistent trend was established for leaf‐P. Leaf‐K was increased at low rate of nitrogen fertilization during tuber formation and maturation whereas leaf‐Ca increased only at tuber maturation in the presence of higher rates of nitrogen fertilization. There was a marked increase in leaf‐Mg at all stages of growth when N treatment was increased to 200 kg N/ha. A positive correlation (r = 0.84???) was obtained for leaf‐K at the vegetative growth stage with tuber yield, while leaf‐Mg was positively correlated with tuber yield at vegetative (r = 0.46?), tuber formation (r = 0.50?) and tuber development (r = 0.67??) stages. All other elements were negatively correlated with yield at all stages of growth. Tuber yield was highest at the 200 kg N/ha treatment.     

The relationship between phosphorus and copper concentrations in wheat

Abstract

Poorly managed kaolinitic soils are often too low in P and K for optimum agronomic crop production. Even though many of these soils have relatively high phosphate fixing capacities, P applied at sufficient rates to increase soil P to acceptable levels may induce micronutrient deficiencies. The purpose of this study was to evaluate the effects of applied and residual P on Mn, Zn, and Cu uptake by field grown wheat (Triticum aestivum). Treatments were a one‐time application of P (0, 64, 128, 256, and 384 kg/ha P) and K (0, 110, 220, 440, and 660 kg/ha K) rates arranged in a 5×5 complete factorial. The treatments were applied in October, 1977 and the study was continued through June, 1979. Potassium and P × K interactions did not have a significant effect on Mn, Zn, or Cu uptake. Phosphorus did not affect Mn concentration in the wheat tissue but Zn and Cu concentrations generally decreased as applied and residual soil P levels increased. The tissue Zn concentration at the various plant growth stages did not decrease below defined critical levels. The Cu concentration decreased linearly with applied P and curvilinearly with residual P. The tissue Cu levels often decreased below suggested critical levels. Total Cu in the wheat tissue indicated that the decrease in Cu concentration as P levels increased was not a simple dilution effect resulting from increased plant growth as applied and residual soil P increased.     

Effect of fertilization and irrigation upon NPK composition of corn leaves,on corn yields,and available k in soil

Abstract

Corn (Zea mays L.) was grown for three consecutive years on Congaree loam to measure the effects of rates of N, P, and K fertilization and irrigation on the nutrient concentration of leaves, the level of available K in the soil, and on the yield of corn. Plant nutrients consisting of 0, 56, 140, 224, and 280 kg N/ha; 0, 15, 37.5, 60, and 75 kg P/ha, and 0, 28, 70, 112, and 140 kg K/ha were applied in a central composite rotatable design in each of the three years. All plant residue was removed each year when the corn was harvested, and the plots remained fallow during the winter months. One half of the experiment was irrigated when there was a 50% depletion of available soil moisture in the 0‐ to 46‐cm soil depth.

Leaf composition was affected by fertilization and irrigation. A rapid decrease in available soil K in the 0‐ to 15‐cm depth was evident the first year with all rates of added K. The decline in available soil K was unaffected by irrigation and levels of applied N and P.

There were consistent yield responses each year to added N, no response to added P, and a response to added K only during the second year.     

Combined Effects on Nitrogen Fertilization and Soil of CaCO3 Contents on Corn Performance in Al-Marj Soil,Libya

A two-year field trial was conducted at Al-Marj Research Center, northeast Libya, during the summers of 1996 and 1997 to examine the effect of nitrogen (N) fertilizers on corn (Zea mays L.) growth in a Libyan soil (fine mixed thermic, Typic Haploxerolls) amended with different calcium carbonate (CaCO₃) levels. Two N fertilizer sources (urea and diammonium phosphate, or DAP) were used at three application rates (0, 80, and 160 kg N/ha). The CaCO₃ treatments were 1%, 6%, and 12% based on the soil weight of a 15 cm furrow slice. A basal phosphorus (P) dose of 46 kg P₂O₅/ha as triple superphosphate was applied to all experimental plots before planting. The experimental plots were arranged in a randomized split-split plot design with three replications. The parameters measured included corn grain weight, plant dry-matter content, leaf contents of N, P, potassium (K), calcium (Ca), and magnesium (Mg). The plant dry matter and corn-grain yield were significantly decreased by CaCO₃, but were significantly increased by N fertilizer rates. Average grain yield dropped from 8 to 3 Mg/ha at 1% and 12% soil CaCO₃ content, respectively. Generally, the N source did not have a significant effect on dry matter or on grain yield. The negative effect of CaCO₃ on yield was associated with concomitant significant reduction in leaf N, P, K, and Mg contents, and an increase in Ca content. However, the leaf levels of these nutrients were considered sufficient for corn growth. Therefore, the reduction of leaf-N by CaCO₃ in fertilized soils might have been the major cause of corn dry-matter and grain-yield reductions.     

Phosphorus relationships in no‐till small grains

Abstract

Phosphorus (P) fertilizer recommendations for no‐till small grain production are poorly defined. These studies were conducted to determine small grain‐P response relative to the Olsen‐P soil test and compare P‐fertilizer placements with the seed and banded below and to the side of the seed under no‐till field conditions. Phosphorus rates of 0 to 26 kg P/ha were evaluated on seven spring barley (Hordeum vulgare L.), 11 spring wheat, and six winter wheat (Triticum aestivum L.) locations in central and northcentral Montana between 1986 and 1990. Grain yield, grain protein, test weight, above‐ground crop yield, plant P concentration at maturity, and P uptake were measured. One winter wheat location had a significant yield response to P; all other locations had non‐significant yield responses. Grain protein, test weight, P concentration, and P uptake were all unaffected by P rate or P placement. Both the ANOVA and paired t‐test were used to analyze the P‐placement data and were all nonsignificant. Slopes of grain yield response (grain yield for each P rate minus the grain yield without P), P concentration, and P uptake versus P rate were analyzed with the t‐test; none of the P‐response slopes were greater than zero. The P responses by individual crop were regressed against P rate, Olsen‐P soil test, available soil water at planting, and pH. Phosphorus rate was not a significant factor in any of the equations. Significant and useful predictive equations for grain yield response could not be generated; however, equations predicting P concentration and P uptake were developed. The Cate‐Nelson graphical analysis was unsuccessful in estimating an Olsen‐P soil test critical level. All attempts failed to relate grain yield or grain yield response to the Olsen‐P soil test and/or P rate. When P soil tests are higher than 12 mg/kg, no‐till grain growers should consider applying a maintenance level of P fertilizer, about 5 to 10 kg P/ha either banded below or with the seed, to maintain soil P levels.     

Vegetative and reproductive dry weight inhibition in nitrogen‐ and phosphorus‐deficient Pima cotton 1

Whether the extent of dry weight inhibition by nitrogen (N) or phosphorus (P) deficiencies on different plant parts is the same and whether imposing moderate N and P deficiencies selectively suppress undesirable vegetative growth has not been studied in Pima cotton (Gossypium barbadense L.). The purpose of this study was to determine the extent to which dry matter accumulation in leaves, stems, and reproductive structures is inhibited by N and P deficiencies in Pima cotton. The study was conducted in 1991 and 1992 in a Uvalde silty clay loam soil (fine‐silty, mixed, hyperthermic Aridic Calciustolls). The treatments included applied rates of 0, 67, 135, 202, and 269 kg N ha^‐1 in a factorial combination with 0, 15, 29, and 44 kg P ha^‐1. Nitrogen deficiency (0 kg N ha^‐1) significantly (P≤0.05) reduced leaf (LDW) and stem (SDW) dry weights in both years and reproductive dry weight (RDW) in 1992. Nitrogen deficiency suppressed dry weight accumulation in leaves to a greater extent than in stems. Relative to 269 kg N ha^‐1, the 0 kg N ha^‐1 treatment resulted in a maximum LDW reduction of 62% at 144 DAP (days after planting) in 1991 and 36% at 121 DAP in 1992, compared with a corresponding SDW reduction of only 39% in 1991 and 25% in 1992. Dry weight accumulation in reproductive parts was the least affected by N deficiency. The decline in LDW associated with senescence and defoliation began earlier in treatments that received 0 or 67 kg N ha^‐1 than treatments that received ≥135 kg N ha^‐1. Phosphorus affected LDW and SDW in 1991, but its differential effect on LDW, SDW, and RDW was much smaller than that of N. Imposing a moderate level of N deficiency, not P deficiency, may be an effective Pima cotton management strategy to selectively suppress undesirable vegetative growth and enhance maturity.     

Navy bean yield and maturity response to nitrogen and zinc 1

Dry bean (Phaseolus vulgaris L.) generally responds to nitrogen (N) fertilizer with increased yields, but N can delay maturity and cause yield and quality losses from early fall frost. Maintaining adequate zinc (Zn) nutrition in bean promotes earlier maturity. This study was conducted to determine if Zn application can overcome maturity delays possible with the N recommended for high bean yields. Three zinc sulfate (ZnSO₄) treatments (0 Zn, 5.6 kg Zn/ha banded adjacent to the row, and 11.2 kg Zn/ha broadcast and incorporated) were applied in combination with five N rates (0, 45, 90, 134, and 179 kg/ha). Whole plants were sampled at the R1 growth stage (onset of flowering) and analyzed for N and Zn content. Maturity was estimated by determining the percentage of mature pods at the R8‐R9 growth stage. Yields were estimated by harvesting 12.2 m of row at maturity. Zinc fertilization generally increased mature‐pod percentages with banded Zn producing the most consistent response. Zinc did not consistently affect bean yield. Yield and mature‐pod percentage generally increased and decreased, respectively, with increasing N rate. Whole‐plant N concentrations increased linearly with increasing N rate but did not differ among Zn treatments. Mean plant Zn concentrations were increased by Zn fertilizer and related well with mature‐pod percentage means. In situations of high available N, short growing seasons, or with late planting, Zn applications can reduce the risk of crop losses from early fall frost.     

不同供磷水平对玉米干物质和磷动态积累及分配的影响

采用田间试验研究了不同供磷水平对玉米干物质和磷动态积累、分配规律及磷肥效率的影响。结果表明,施磷增加玉米茎、叶、穗轴、子粒和整株干重及磷含量,降低磷肥表观利用率、农学效率和生理利用率。随生长推进,不同供磷水平的子粒和整株干重及磷含量不断增加直到成熟,其余器官干重和磷积累峰值出现时间早晚不同;生长后期,子粒成为唯一的库器官,茎、叶、根,甚至穗轴均成为源,有一部分光合产物和磷输出,被重新分配到子粒。出苗后79～100 d,各供磷水平下的子粒干重净增量是相应出苗后58～79 d的0.75～1.02倍;前者子粒磷净增量是相应后者的1.56～2.39倍,说明光合产物和磷向子粒中运输不是同步的过程。同一取样时期,随施磷量增加,各器官的干重和磷含量增加,以施P2O5 90 kg/hm2最好,产量达11231.6 kg/hm2,原因是该处理的玉米穗长、行粒数和单株粒重显著增加,禿尖长度显著减少。     

Soil chemical properties after long‐term n fertilization of bromegrass: Nitrogen rate

Abstract

Nitrogen (N) fertilizers increase yield and quality of grass forage, and may also alter soil chemical properties. A field experiment was conducted in south‐central Alberta to determine the effect of long‐term application of ammonium nitrate to bromegrass on concentration and downward mobility of soluble NO₃‐N, extractable NH₄‐N, P, Ca, Mg, and K, and total C and N in a Thin Black Chernozemic loam soil. The fertilizer was applied annually in early spring for 16 years at 0 to 336 kg N/ha. There was little accumulation of NO₃‐N in the soil at N rates of 112 kg/ha or less. However, at rates higher than 112 kg N/ha there was accumulation of NO₃‐N in the 15–30 and 30–60 cm layers, but very little in the 90–120 cm depth. The NH₄‐N accumulated in the 0–5 cm layer when the fertilizer was applied at rates between 168 to 280 kg N/ha and in the 5–10 cm layer at N rates exceeding 280 kg/ha. There was a decline in extractable P in soil with N application up to 84 kg N/ha rate, while it increased with high N rates. The increasing amounts of applied N resulted in a decline in extractable soil Ca, Mg and K, and this decrease was more pronounced in the 0–5,5–10,10–15, and 15–30 cm layers for K, 0–5 and 5–10 cm layers for Ca, and 0–5, 5–10, and 10–15 cm layers for Mg. There was a build‐up of total C and N in the surface soil with increasing rate of applied N.     

Variation in content of available P and K (bray I) in soil samples from a cropped N,P, and K fertility experiment over 8 years

Abstract

Plots from a N, P, and K field fertility experiment were soil sampled each spring and fall from 1971 to 1979 to study the effect of cropping and different rates of added P and K on the content of available soil P and K (Bray I). Phosphorus and K fertilization was in the spring after soil sampling and before planting in 1971, 1972,and 1973 and in the fall after sampling in 1974, 1975, 1976, 1977, and 1978. Over the 8‐year period, available soil P increased 1 kg/ ha for every 2.3 kg/ha of added P; while available soil K increased 1 kg/ha for every 5.7 kg/ha of added K. However, within a growing season and between growing seasons, contents of available soil P and K showed cyclic patterns, increasing and decreasing to a greater extent than the long‐term response. Changes in available P and K from spring to fall and from fall to spring are presented. Variability in the content of available soil P and K for 32 plots receiving a similar treatment of either P or K was greater for P as compared to K.     

Seasonal growth and composition and accumulation of N‐P‐K in dryland and irrigated pumpkins

Growth and N‐P‐K uptake in pumpkin (Curcubita moschata Poir.) cv ‘Libby‐Select’ were studied in dryland and irrigated culture. In both moisture regimes, maximum rates of dry matter accumulation occurred between the early and mid‐fruiting developmental stages. Higher total dry matter production with irrigated than dryland culture was primarily associated with increased shoot growth. Concentrations of N, P, and K in foliage generally decreased as pumpkin age increased. Irrigated pumpkins in conjunction with higher total vegetative dry matter accumulated more N, P, and K than dryland pumpkins. Up through early fruit development, N, P, and K accumulation was primarily in leaves and vines and by the late growth stages was almost entirely in the fruit. Total N, P, and K uptake at late fruiting was estimated at 219, 32, and 228 kg/ha in irrigated pumpkins and 180, 21, and 177 kg/ha in dryland pumpkins. Approximately 58% of the N, 52% of the K, and 68% of the P accumulated by late‐fruiting was absorbed by the plant after the early‐fruiting stage in both moisture regimes. Potassium redistribution from vegetative tissues during late fruit development decreased foliar K contents 32% in dryland pumpkins and 21% in irrigated pumpkins.     

Yield and quality of fennel (Foeniculum vulgare Mill.) in relation to basal and foliar application of nitrogen and phosphorus

A split‐plot field trial was conducted to study the effect of foliar application of 0 kg/ha (control), 20 kg N/ha, 2 kg P/ha or 20 kg N + 2 kg P/ha at two basal levels, viz., 90 kg N + 40 kg P/ha (optimal dose) and 60 kg N + 27 kg P/ha (sub‐optimal dose). Each group received 50 kg K/ha, which was applied uniformly on the yield and quality of fennel. Spray was applied at the flowering stage, 120 days after sowing.

The optimal basal dose gave better results than did the sub‐optimal one. Spray of 20 kg N + 2 kg P/ha proved optimum. This spray proved more effective at sub‐optimal than at optimal basal dose. The percentage of anethole (but not of fenchone) in the essential oil was significantly higher in plants grown with the sub‐optimal basal dose. Foliar application of N, P and N + P, on the other hand, decreased the anethole content of oil and increased that of fenchone significantly. Hence, foliar feeding may be recommended if the oil is required for perfumery and confectionary industries.     

Response of cauliflower to phosphate fertilizer placement and soil test phosphorus calibration on a Karrakatta sand

Abstract

The effect of placement (broadcast versus banded) and level of phosphorus (P) applied as superphosphate at 0 to 450 kg P/ha was measured using the yields of cauliflower (Brassica oleracea var botrytis) on newly cleared Karrakatta sands of low natural P fertility. While there was a significant (P<0.01) yield response to level of P, there was no significant response to fertilizer placement. Phosphorus recovery efficiency by curds (P uptake curds/P applied both in kg/ha) decreased from 0.35 at 20 to 0.09 at 320 kg applied P/ha. Phosphorus recovery efficiency by whole plants decreased from 0.58 at 20 kg P/ha to 0.18 at the highest level. Bicarbonate‐soluble P extracted from the top 15 cm of soil was determined on residual P sites from experiments over two years where P was applied from 0 to 450 kg P/ha. These soil test values were related to yield. The critical soil test values required for 95 and 99% of maximum yield were 40 and 55 (μg/g, respectively. The level of freshly‐applied P required for either 95 or 99% of maximum yield varied from 108 to 175 kg P/ha, respectively at <5 μg/g soil test P to 0 at the critical values. Phosphorus in the youngest expanded leaf at buttoning required for 95 and 99% of maximum yield was 0.46±0.02 and 0.47±0.02%, respectively.     

Elemental leaf content and deficiency symptoms in rabbiteye blueberries: 1. Nitrogen

Rabbiteye blueberries grown in sand culture were subjected to varying levels of N fertilization (0 ‐ 81 mg N/liter) applied in aqueous solution at the rate of 250 ml/plant daily. Essential elements other than N were kept constant. Shoot growth and leaf concentration of N, P, K, Mg, Ca, Mn, Fe, Cu, B, Zn, Co, and Al were determined. Shoot growth and percent leaf N increased with increased N levels. Shoot growth increased little at N fertilization levels of 0 ‐ 9 mg/ liter but increased rapidly at higher rates. N content in leaves followed a quadratic curve, with % N in leaves increasing more rapidly from 0 to 27 mg N/liter than from 27 to 81 mg N/liter fertilization levels. Leaf concentration of K, Ca, Mg, Mn, B, and Ca decreased linearly as N levels increased. Total content of all elements increased as N fertilization increased. Visual N deficiency became increasingly evident as % N content decreased below 1.4% N.

Nitrogen, the most utilized element in plants, is usually the first to become deficient in sandy soils low in nutrient content (1). Rabbiteye blueberries (Vaccinium ashei Reade) are often grown on acidic, sandy, upland coastal plains soils that are low in cation exchange capacity, organic matter content, and available nutrients. In these acidic soils, NH₄N is more available than in neutral soils (2). The NH₄N source appears to be more suitable for blueberry growth, resulting in greater nutrient uptake, plant growth, and % N of leaf tissue than did the NO₃N sources (5,6).

Nitrogen deficiency symptoms in rabbiteye blueberries are characterized by small, yellow and/or red leaves and stunted plants (3). Since young rabbiteye plants are very sensitive to fertilizer, similar chlorosis symptoms (yellowing or reddening of leaves) can be associated with over‐fertilization, possibly due to root damage (7). Cain (2) found that leaves from healthy container‐grown highbush (V. corymbosum L.) blueberry plants contained about 2% N and higher levels of K and Ca than field‐grown plants. Greenhouse and Field studies indicate that leaf N content in rabbiteye blueberries is usually lower, ranging from about 1.5 to 1.8 (3,7,8). Increased N fertilization decreased the nutrient uptake of other essential elements (Ca and Mg) in rabbiteye blueberries (6). In highbush, Popenoe (4) indicated that a depression of P and K might occur under conditions of high N levels.

This study was initiated to ascertain the effect of NH₄N fertilization levels on uptake patterns of essential elements and to determine the relationships of N fertilization, leaf N content, plant growth, and visible deficiency symptoms.     

Effect of intensively cropping greenhouses in semiarid regions on soil salinity and nitrogen fertilizer requirements of cucumber

The soil of a greenhouse located in the semiarid Lebanese coast of the Mediterranean sea, and which has been in intensive crop production for the past ten years, was chemically analyzed. Results were: NO₃‐N = 225 ppm, NH₄‐N = 56 ppm, pH = 7.0 and salinity (ECe) = 2.5 dS/m. Irrigation water salinity (ECw) = 0.4 dS/m. Cucumber (Cucumis sativus L. cv. Lolita), a parthenocarpic beit‐alpha type plant, was grown in this greenhouse, and was treated with nitrogen (N) fertilizer at the rates of 0, 81 and 162 kg N/ha. The N was split into six equal weekly applications, with the first application made on the first week of fruit production. Total fruit yield for the first 8 weeks of harvest was 71.4, 63.4 and 60.2 ton/ha for the plots receiving 0, 81 and 162 kg N/ha, respectively. Leaf petiole NO₃‐N concentration was higher than the recommended level in all treatments throughout the experiment. At last harvest, NO₃‐N concentration in leaf petiole was 12500, 15500 and 19500 ppm in plants receiving 0, 81 and 162 kg N/ha, respectively. Soil salinity has sufficient to cause yield reduction for many greenhouse crops. In contrast, soil mineral N has sufficient to meet the N requirement for an entire season for many annual crops.     

Effects of nitrogen fertilization method and tillage system on squash growth,nutrient uptake and fruit yield

Abstract

Squash, cv Dixie, grown on a Lakeland sand was subjected to factorial combinations of 3 tillage systems and 2 N application methods during 1979 and 1980. Fruit yield was greatest with a combination of moldboard plow tillage and application of 22 kg N/ha preplant and 18 kg/ha increments of N by fertigation 2, 3, 4, 5 and 6 weeks after planting. Plant growth and nutrient uptake were greatest and N available for potential contamination of the ground‐water was least with subsoil‐bed tillage and N application by fertigation. Disc harrow tillage with 67 kg N/ha preplant and 45 kg N/ha 4 weeks after planting resulted in 42% less yield, 61% less plant growth, 29 to 64% less nutrient uptake and more than 5 times as much N available for potential contamination of the groundwater as the best practices.     

Annual ryegrass response to limestone and phosphorus on an ultisol 1

Decreasing winter pasture productivity in unlimed Ultisols has been associated with increased soil acidity due to fertilizer N application. The susceptibility of cool season grasses to soil acidity and associated infertility factors that result in reduced forage yield are not well understood. This field study was undertaken to evaluate the effects of factorial combinations of limestone and P applications on annual ryegrass (Lolium multiflorum Lam. ‘Marshall') dry matter production and tissue mineral concentrations on a strongly acid (pH 4.7), sandy soil. Limestone was applied to a Lilbert loamy fine sand (loamy, siliceous, thermic, arenic Plinthic Paleudult) at rates of 0, 672, or 3808 kg ha^‐1. Phosphorus was applied to split plots at rates of 0, 30, 60, 90, 120, 240, or 480 kg P ha^‐1. Over three harvest years, ryegrass yields increased 90 to 750% and 25 to 80% at the highest lime and P rates, respectively. In the second year, yield response to applied P was significantly less at the high lime rate which indicated that liming made soil P more plant available. Lime and applied P increased plant tissue P, Ca, and Mg concentrations. Yield was positively correlated with soil pH, P, Ca, and Mg and negatively related to soil K and Al. Clear relationships between individual soil test levels and leaf mineral concentrations with yield fluctuations could not be established because these variables were inextricably related to the lime and P rates. Nevertheless, excessive soil Al, coupled with inadequate P, Ca, and Mg availability, were indicated as important nutritional factors limiting annual ryegrass growth in unlimed soil.     

Influence of rates and sources of nitrogen on growth,nitrogen uptake and yield of cotton (G. hirsutum L.)

Field experiments on cotton with different forms of urea applied at rates of 40 and 80 kg N/ha were carried out. The results indicated that application of nitrogen increased plant height, dry matter accumulation, number of bolls per plant, seed cotton yield and nitrogen uptake. The proportion of dry matter and nitrogen in the stem was increased and that in the leaves was reduced by N application. Sulphur coated urea (all applied at sowing) was about the same in effect as N-Serve treated urea and gave significantly more seed cotton yield than untreated urea, neem cake treated urea and sulphur coated urea (applied in two splits). Nitrogen efficiency as expressed by kg seed cotton production per kg N applied was greater with 40 kg N/ha rate than with 80 kg N/ha. Sulphur coated urea (all applied at sowing) gave the highest nitrogen efficiency followed by N-Serve treated urea.