Nitrogen Accumulation in Soybean Following Defoliation

The effects of defoliation on soybean [Glycine max (L.) Merr.] growth and yield have been well studied, but relatively little is known about its nitrogen (N) accumulation after defoliation. An experiment was conducted to examine soybean recovery and N accumulation following defoliation. The indeterminate cultivar (‘Tousan 69’) was planted in a greenhouse, and two defoliation treatments (no defoliation and 67% defoliation) were imposed at the R₂ stage when plants had at least one flower in the two uppermost nodes. At 0, 15, 30 and 45 days after defoliation (DAD), plants were destructively sampled to measure dry mass production, nitrogen accumulation and nitrogen fixation. Seed yield and N concentration also were measured at maturity. Neither the seed yield nor its N concentration was affected by defoliation. Although defoliation temporarily reduced soybean dry weight and N accumulation during 15 DAD, defoliated plants completely recovered their dry weight and N accumulation 30 DAD. There was little difference in N concentration between defoliated and non defoliated plants, indicating that N acquisition was restored during the recovery process. Recovery of N accumulation in defoliated plant was due to complete recovery of N₂-fixing ability and maybe related to improvement in N absorption after defoliation.     

Effect of Fish Silage on Yield and Chemical Composition of Italian Ryegrass (Lolium multiflorum Lam.)

Seed production of spinach (Spinacea oleracea L.) is positively affected by increasing the amounts of nitrogen (N); however, regulations restrict the application rate of N in Danish agriculture. The aim of our study was to test different N application strategies in spinach seed production and their effects on N concentration, seed yield, seed weight and germination. A total amount of 100–150 kg N ha^?1 was broadcast or placed at sowing or applied as a split application at sowing and pre-elongation at the Danish Institute of Agricultural Sciences, location Flakkebjerg. Seed yields were positively affected by the high N applications, but no difference was observed between 150 kg N ha^?1 broadcast at sowing, and 40 kg N ha^?1 broadcast at sowing with an additional late application at a rate based on soil mineral N analysis. No consistent pattern was observed between N management strategy and seed weight or N management strategy and germination. A high N concentration in the plants at the start of growth showed negative effects on final seed yield, whereas later in the season there was a significantly positive correlation between N concentration in the plants and seed yield. A soil mineral analysis can be used as a tool to adjust the N application rate when a split application strategy is chosen.     

适宜氮肥可提高人工羊草的抽穗数和种子产量

【目的】 施用氮肥是禾本科牧草种子高产的关键管理措施之一。为提高羊草种子产量,在人工羊草地上探讨施用氮肥对羊草种子产量及其构成因子的影响,以期为羊草种子生产提供理论和实践依据。 【方法】 试验于 2013～2015 年进行,以中科 2 号羊草 [Leymus chinensis (Trin.) Tzvel ‘Zhongke No.2’] 为材料,设置 5 个氮肥处理水平,分别为 N 0、60、120、180、240 kg/hm2,氮肥在返青期 (4 月上旬) 和种子完熟后 (7 月下旬) 施入,两个时期各施 1/2,羊草种子完熟时测定种子产量和产量构成因子。 【结果】 施氮量和年际对种子产量影响显著。随生长年限延长,羊草种子产量逐年增加。2013 年和 2014 年种子产量随施氮量增加呈先增加后降低的趋势,2013 年施用氮肥 104.9 kg/hm2 时羊草产量最高,为 395.2 kg/hm2,但氮肥对种子产量影响不显著,2014 年施用氮肥 173.5 kg/hm2 时产量最高,为 857.8 kg/hm2,较不施氮肥显著增加 56.0%。2015 年种子产量随施氮量增加而增加,施用氮肥 180 kg/hm2 时种子产量达较高水平为 1865.0 kg/hm2,与施用氮肥 240 kg/hm2 差异不显著,较不施氮肥显著增加 206.5%。通径分析结果表明,种子产量与抽穗数呈极显著正相关 ( r = 0.883, P < 0.01),抽穗数对种子产量的直接作用最大为 0.717,分蘖数对种子产量的间接作用最大为 0.689,且主要是通过抽穗数产生,抽穗数对种子产量的贡献最大。2013 年施用氮肥羊草抽穗数差异不显著,其后两年随氮肥施用量增加抽穗数的变化趋势与产量相同。三年连续施用氮肥使 2014 年和 2015 年抽穗数显著增加,对种子生产有利。施用氮肥显著增加羊草植株穗长、小穗花数、结实粒数/穗和结实率,而对千粒重和小穗数影响不显著。抽穗数与穗长、千粒重和小花数/小穗呈显著负相关。 【结论】 随生长年限增加,羊草种子高产所需施氮量增大,羊草适宜施氮量为 104.9～180.0 kg/hm2,2013 年以施氮 104.9 kg/hm2 为宜,而 2014 年和 2015 年则以 180 kg/hm2 左右为宜。抽穗数是影响种子产量的最关键因子,不受当年施用氮肥的影响,而与前一年种子完熟后施氮量和 8～10 月降雨量相关。抽穗数增加导致的穗长、千粒重和每小穗花数减少,可以通过添加氮素来给予补偿。      

Effects of phosphorus and zinc on soyabean in Sierra Leone

Abstract

The effects of P and Zn rates on soybeans were investigated on Njala upland soil. There was a moderate positive linear effect of rates of P upon number of nodules. Also, there was a highly significant linear effect of P upon nodule weight and the quadratic effect was moderately significant. There was a significant negative effect of Zn upon nodule weight. Statistically significant linear and curvilinear trends associated with P rates affected dry matter at 50% flowering.

Seed yield was significantly affected by rate of P and there was a highly significant positive linear effect of P upon seed yield. Percent protein in seed was not affected by either P or Zn rates. Rates of Zn did not significantly affect number of nodules, dry matter, pods per plant and seed yield. There were highly significant correlations among number of nodules, nodule weight, dry matter, pods per plant and seed yield.     

Rhizobium and phosphorus influence on lentil seed protein and lipid

Root nodulation by rhizobial bacteria and P fertilization may affect seed protein and lipid composition in plants by altering nitrogen (N) and phosphorus (P) nutrition or by eliciting metabolic responses by the host plant. This study was conducted to determine the effects of rhizobium and P fertilization on seed protein and lipid contents and yield of lentil (Lens culinaris Medik). Lentil was grown to maturity in a greenhouse with P levels of 0 (low) and 50 (high) mg kg^‐1 soil with or without inoculation with Rhizobium bacteria. At the low level of P, protein and lipid concentrations and protein contents were significantly higher in inoculated than in uninoculated plants. Seed dry weight and protein concentrations and contents were higher in inoculated than in uninoculated plants at the high level of P. Seed protein/lipid (Pro/L) concentration ratios varied between inoculated and uninoculated plants at both P levels, and was related to the intensity of root nodulation. Lipid and protein contents were highly correlated with P content in lentil seeds. Seed lipid and protein contents were lower at the high level of P in uninoculated than inoculated plants. The data indicate different patterns of seed P accumulation and different relationships between seed P content and protein and lipid contents in inoculated and uninoculated plants. This might indicate that the intensity of nodulation altered the response of seed protein and lipid metabolism to increasing P availability, which affected protein and lipid ratios.     

Effect of seed phosphorus concentration on nodulation and growth of three common bean cultivars

Abstract

An experiment was conducted in the greenhouse to evaluate the effects of seed phosphorus (P) concentration on growth, nodulation, and nitrogen (N) and P accumulation of three common bean (Phaseolus vulgaris L.) cultivars. Seeds were produced under low or high soil P levels, and soaked, or not, in 200 mM KH₂PO₄ solution. The experiment had a 3×3×2×2 factorial block design: three cultivars (ICA Col 10103, Carioca and Honduras 35), three levels of applied P (15, 30 and 45 mg P kg^?1 soil), two native seed P concentrations, and two seed soaking treatments. Plants were harvested at flowering. Soaked seeds increased the number, dry mass and P content of nodules, but did not affect plant growth. Plants originated from seeds with high native P concentration presented higher shoot dry mass and nodule number and mass at every soil P level, and were less responsive to increased soil P supply, than plants from low seed P. In plants from seeds with high P, soil P levels did not alter significantly root dry mass, while in plants from seeds with low P bean cultivars expressed wider differences in root dry mass. The genotypic variability of nodulation was influenced by soil P levels and seed P concentration. Both higher soil or seed P supply enhanced N and P accumulation in shoots. These results indicate that a high seed P concentration produces plants less dependent on soil P supply, and can enhance nodulation and N₂ fixation of common bean. Seed P supply affected the cultivar performance, and should be considered in evaluation of bean genotypes.     

Crop improvement and root rot suppression by seed bacterization in chickpea

Abstract

Field experiments were conducted at the Regional Research Station, CCS Haryana Agricultural University, Bawal, India, to evaluate the contribution of different bioinoculants in terms of nodule number, nodule biomass, root rot incidence and seed yield in chickpea. Nodule number and biomass were positively affected by the application of bioinoculants. Plant growth promoting rhizobacteria (PGPR) alone or in combination with bioinoculants reduced plant mortality and increased seed yield of the crop. Seed yield at 50% fertilizer dose (RF) plus all the three inoculants was at a maximum during all the three years of experimentation.     

Spring camelina N rate: balancing agronomics and environmental risk in United States Corn Belt

Camelina (Camelina sativa (L.) Crantz) seed oil has desirable properties for producing advanced biofuels and as a healthy cooking oil. It has been grown for centuries, but basic recommendations for nitrogen (N) fertilizer requirements are still needed to support widespread industrial cultivation across North America. A replicated N-response plot-scale study was conducted on a northern Mollisol soil for two growing seasons to 1) determine seed and oil yield, seed oil content, and vegetative response; 2) determine indices of N use efficiency; and 3) measure post-harvest residual inorganic soil N as an index of environmental risk. Seed and oil yield response to N fertilization was described with a quadratic function, which predicted maximum seed yield (1450 kg ha^?1) and oil yield (580 kg ha^?1) at about 130 kg N ha^?1. However, seed and oil yield did not differ significantly among N-rates above 34 kg N ha^?1. Seed oil content averaged 400 g kg^?1 among all N rates. Agronomic efficiency declined above 34 kg N ha^?1, which coincided with an increase of post-harvest soil nitrate-N plus ammonium-N (residual N). Considering N use efficiency, simple cost analysis, and risk associated with residual N, a rate of 34 kg N ha^?1 is recommended.     

Grain yield,stalk rot,and mineral concentration of fertigated corn as influenced by N P K

Peanut (Arachis hypoaaea L.) is a major cash crop in Georgia. Corn (Zea mays L.) is the preferred rotation crop, but is often not profitable because of large inputs costs. Fertilizer comprises approximately 50% of the variable production costs of irrigated corn. There is interest in reducing fertilizer inputs, in particular N, to reduce variable costs and decrease nitrate leaching to groundwater, but yields may suffer. Our objective was to investigate the effect of N, P, and K fertilizer rates on the yield of N‐fertigated corn in a corn/peanut rotation. Field experiments were conducted during 1987 and 1988 on a Tifton loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudult) at Tifton, GA. Treatments were three rates each of N, P, and K fertilizer in a complete factorial. Nitrogen, P, and K rates were 168, 252, 336 kg N ha^‐1 yr^‐1; 44, 73, 103 kg P ha^‐1 yr^‐1; and 84, 223, and 363 kg K ha^‐1 yr^‐1, respectively. Grain yields were large, 12.6 and 10.4 Mg ha^‐1 in 1987 and 1988, respectively, but not affected by N, P, or K rate. Since the lower rates of N, P, and K were less than recommended, fertilizer use efficiency for fertigated corn can be improved, for at least one year, by reducing N, P, and K fertilizer rates to less than current recommendations. Rates of N, P, and K did not result in a substantial difference in the concentration of essential nutrients. Stalk rot was limited (< 15%), but decreased with increasing K fertilizer rate.     

Do interactions with soil organisms mediate grass responses to defoliation?

Defoliation-induced changes in grass growth and C allocation are known to affect soil organisms, but how much these effects in turn mediate grass responses to defoliation is not fully understood. Here, we present results from a microcosm study that assessed the role of arbuscular mycorrhizal (AM) fungi and soil decomposers in the response of a common forage grass, Phleum pratense L., to defoliation at two nutrient availabilities (added inorganic nutrients or no added nutrients). We measured the growth and C and N allocations of P. pratense plants as well as the abundance of soil organisms in the plant rhizosphere 5 and 19 d after defoliation. To examine whether defoliation affected the availability of organic N to plants, we added ¹⁵N-labelled root litter to the soil and tracked the movement of mineralized ¹⁵N from the litter to the plant shoots.When inorganic nutrients were not added, defoliation reduced P. pratense growth and root C allocation, but increased the shoot N concentration, shoot N yield (amount of N in clipped plus harvested shoot mass) and relative shoot N allocation. Defoliation also reduced N uptake from the litter but did not affect total plant N uptake. Among soil organisms, defoliation reduced the root colonization rates of AM fungi but did not affect soil microbial respiration or the abundance of microbe-grazing nematodes. These results indicate that interactions with soil organisms were not responsible for the increased shoot N concentration and shoot N yield of defoliated P. pratense plants. Instead, these effects apparently reflect a higher efficiency in N uptake per unit plant mass and increased relative allocation of N to shoots in defoliated plants. The role of soil organisms did not change when additional nutrients were available at the moment of defoliation, but the effects of defoliation on shoot N concentration and yield became negative, apparently due to the reduced ability of defoliated plants to compete for the pulse of inorganic nutrients added at the moment of defoliation.Our results show that the typical grass responses to defoliation—increased shoot N concentration and shoot N yield—are not necessarily mediated by soil organisms. We also found that these responses followed defoliation even when the ability of plants to utilize N from organic sources, such as plant litter, was diminished, because defoliated plants showed higher N-uptake efficiency per unit plant mass and allocated relatively more N to shoots than non-defoliated plants.     

氮、磷、钾、硼肥对甘蓝型油菜籽品质的影响

以多个正在大面积应用的甘蓝型油菜品种为研究对象,在长江流域冬油菜主产区的10个省（市）布置氮、磷、钾和硼肥田间肥效试验共284组,通过多点试验分别探讨当前生产条件下施用氮、磷、钾、硼肥对双低和双高甘蓝型油菜籽含油量、蛋白质、芥酸、硫甙的影响。结果表明,双低油菜籽平均含油量为41.66%,双高油菜含油量明显低于双低油菜,仅为38.92%。氮、磷、钾和硼肥施用对油菜籽的品质效应在不同试验点表现不尽相同,其总体趋势是:在磷、钾、硼肥基础上施用氮肥提高籽粒蛋白质含量而降低油分含量,且随氮肥用量的增加效果更明显,施氮对双高油菜油分及蛋白质含量的影响程度大于双低油菜;施磷、钾或硼肥有提高油菜籽含油量而降低蛋白质含量的趋势;施肥对油菜籽硫甙和芥酸含量有一定影响,但对品质影响不大。油菜籽含油量与收获指数、千粒重显著正相关,与蛋白质含量呈负相关。研究结果显示,在施氮的基础上配合施用磷、钾和硼肥能减少因施氮引起的油分损失。     

Dry matter production,nutrient uptake,and growth of cotton as affected by potassium fertilization

Insufficient potassium (K) nutrition produces detrimental effects on cotton (Gossypium hirsutum L.) lint yield and fiber quality. To further understand the deleterious effects caused by K deficiency, a 2‐yr (1991 and 1992) field study was conducted to determine how dry matter partitioning and nutrient concentrations of various plant tissues for the cotton genotypes, ‘DES 119’ and ‘MD 51 ne’, were altered by varying the application rate of fertilizer K and nitrogen (N). All plots received a preplant application of 112 kg N ha^‐1, and half of the plots were later sidedressed with an additional 38 kg N ha^‐1. Within each N treatment, half the plots received 112 kg K ha^‐1, preplant incorporated, with the remaining plots not receiving any fertilizer K. Dry matter harvests were taken three times in 1991 and two times in 1992. At cutout (slowing of vegetative growth and flowering), plants that received K fertilization had a 14% more leaf area index (LAI), a 3% increase in the number of main stem nodes, and a 2% increase in plant height. However, those plants had a 12% lower specific leaf weight (SLW) than plants receiving no K fertilization. By the end of season, the of K fertilization had resulted in more stem (21%), bur (13%), seed (19%), and lint weight (20%), but harvest index was not affected. Varying the level of N fertilization did not affect any of these dry matter parameters at any harvest. In general, the larger plants produced under K fertilization had reduced concentrations of N, phosphorus (P), magnesium (Mg), and sodium (Na) in the various plant parts. While N uptake efficiency was not affected by K fertility, plants that received K fertilization had increased efficiency of fertilizer N use and of N utilization within the plant. The smaller LAI of the K deficient plants probably reduced the photosynthetic capacity per plant. A reduced assimilation capacity could explain the inefficiency of N use, lint yield reductions, and poorer fiber quality often associated with K deficiencies.     

Efficiency and response of sunflower to rate and timing of banded nitrogen

Abstract

Nitrogen use efficiency and response of sunflower (Helianthus annuus L.) to timing and rate of surface banded N was characterized in a split‐plot 4x2 factorial experiment. Nitrogen rates (main plots) were 0, 34, 67, and 134 kg ha^‐1 at Mississippi State and 0, 45, 90 and 180 kg ha^‐1 at Brooksville, MS. Nitrogen, applied as NH₄NO₃, was surface banded either at planting or at the four leaf stage (subplot). Seed yield was significantly influenced by rate of N application at both locations. Seed yield showed a quadratic response at Mississippi State and a Mitscherlich‐type response at Brooksville. Maximum seed yields of 2606 and 2380 kg ha^‐1 were obtained at the respective sites. Sunflower responded to N fertilizer application when inorganic N content of the soil to 60 cm depth at planting was less than 50 kg ha^‐1. Nitrogen efficiency was influenced by rate and timing of application, exhibiting exponential declines with increasing N rates. Fertilizer losses at the highest rates of applied N were 19 and 52% at Mississippi State and Brooksville, respectively. Clay‐fixed NH^⁺ accounted for 26% of the applied N fertilizer loss at Brooksville. Nitrogen fertilizer efficiency and recommendations for sunflower could be improved if initial soil inorganic N is taken into account.     

利用15N示踪研究不同肥力土壤棉花氮肥减施的产量与环境效应

【目的】华北平原棉区中等肥力棉田经济最佳施氮量为300 kg/hm2左右,这一结果仅从产量效应得出,未充分考虑棉花对氮肥的回收利用和土壤中氮肥的残留。探讨低肥力土壤施氮量及施氮比例对棉花产量及氮肥利用率的影响,以及低、中、高肥力土壤条件下等量施氮效应,旨在为棉花减氮增效提供理论依据。【方法】田间试验选择了高 (S1)、中 (S2)、低 (S3) 三个肥力水平的地块,其全氮含量分别为0.83、0.74、0.60 g/kg。低肥力地块设置低氮 (N1 113 kg/hm2)、中氮 (N2 225 kg/hm2)、高氮 (N3 338 kg/hm2) 3个氮肥用量;中肥力和高肥力地块设低氮量处理,氮肥两次追施在苗期与初花期进行,氮肥比例为1∶2;此外,设置低肥力土壤低氮量,氮肥追施在苗期与初花期进行,氮肥分配比例为1∶1。在吐絮70%时采集棉株和土壤样品,用15N技术分析了棉株氮素吸收来源、籽棉产量、棉株氮肥回收率和土壤氮肥残留率。【结果】低氮处理,土壤肥力对棉花籽棉产量无显著影响,随土壤肥力提升,棉株吸收氮素来源于肥料的比例下降,相对增加了对土壤氮素的吸收。棉花植株15N回收率随施氮量增加显著下降,随土壤肥力提高呈下降趋势,低肥力土壤与中肥力土壤间棉花植株15N回收率差异不显著,但显著高于高肥力土壤。高肥力土壤15N残留率高于低肥力土壤和中肥力土壤。15N损失率随施氮量和土壤肥力提高显著增加。低土壤肥力低氮量条件下氮肥分配比例1∶2处理籽棉产量高于1∶1处理。低肥力土壤条件下,中氮处理籽棉15N积累量相对高于高氮和低氮处理,籽棉产量较优。【结论】在较低土壤肥力条件下,施氮225 kg/hm2籽棉产量和氮回收率均优于施氮338 kg/hm2,氮肥损失率较低,减氮增效是可行的。高肥力土壤条件下减少氮肥投入可减少肥料的浪费。     

BIG BLUESTEM RESPONSE TO FERTILIZER AND DEFOLIATION ON THE LOUISIANA COASTAL PLAIN

Although big bluestem (Andropogon gerardii Vitman) is used for forage and conservation in the Great Plains, potentially useful Louisiana ecotypes have received little attention. Cloned plants from a robust big bluestem plant collected near Rosepine, LA were assessed for responses to fertilizer and defoliation in a field evaluation of potential forage value. Annual application of nitrogen fertilizer at 50 kg ha^?1 did not increase herbage yield until the third year. Clipping twice annually decreased productivity compared to once annually after the second year. Fertilizer effects on forage nutritive value were small. Clipping improved late-season nutritive value largely due to greater stem development of previously undefoliated plants. Limited responsiveness to fertilization and detrimental effects of repeated defoliation on productivity indicate that even this robust local big bluestem ecotype provides little potential as a pasture plant. Potential is indicated for other uses including wildlife habitat and grassland ecosystems managed for conservation purposes.     

15N study on the partitioning of the nitrogen taken by soybeans from atmospheric dinitrogen,medium nitrate or ammonium

Abstract

Soybean plants (Glycine max, cv. Akisengoku) were water-grown in a greenhouse with a low concentration of nitrate in the culture solution. Under these conditions root nodulation mostly on primary roots was profuse. At the vegetative and pod-filling stages, plants were fed ¹⁵N-labeled dinitrogen, nitrate, or ammonium for 7 to 8 hr in the daytime.

Partitioning of the ¹⁵N from the three nitrogen sources showed distinct characteristics. The nitrogen (N) from dinitrogen preferentially distributed to the developing organs, young leaves, and developing pods, in comparison with N from nitrate. N from ammonium showed distribution pattern similar to that of N from dinitrogen.

The nodule N was supplied by both directly fixed-N and transferred nitrogen, and fixedN was inferred to play a major role in this process. The pro tein N in the roots could be furnished by the recycled N of dinitrogen and nitrate through the shoots along with direct incorporation of amino acids produced in the roots from nitrate     

Influence of Long-term Tillage,Straw, and N Fertilizer Management on Crop Yield,N Uptake,and N Balance Sheet in Two Contrasting Soil Types

Field experiments (established in autumn 1979, with monoculture barley from 1980 to 1990 and barley/wheat–canola–triticale–pea rotation from 1991 to 2008) were conducted on two contrasting soil types (Gray Luvisol [Typic Haplocryalf] loam soil at Breton; Black Chernozem [Albic Agricryoll] silty clay loam soil at Ellerslie) in north-central Alberta, Canada, to determine the influence of tillage (zero tillage and conventional tillage), straw management (straw removed [S_Rem] and straw retained [S_Ret]), and N fertilizer rate (0, 50 and 100 kg N ha^?1in S_Ret, and only 0 kg N ha^?1in S_Rem plots) on seed yield, straw yield, total N uptake in seed + straw (1991–2008), and N balance sheet (1980–2008). The N fertilizer urea was midrow-banded under both tillage systems in the 1991 to 2008 period. There was a considerable increase in seed yield, straw yield, and total N uptake in seed + straw with increasing N rate up to 100 kg N ha^?1 under both tillage systems. On the average, conventional tillage produced greater seed yield (by 279 kg ha^?1), straw yield (by 252 kg ha^?1), and total N uptake in seed + straw (by 6.0 kg N ha^?1) than zero tillage, but the differences were greater at Breton than Ellerslie. Compared to straw removal treatment, seed yield, straw yield, and total N uptake in seed + straw tended to be greater with straw retained at the zero-N rate used in the study. The amounts of applied N unaccounted for over the 1980 to 2008 period ranged from 1114 to 1846 kg N ha^?1 at Breton and 845 to 1665 kg N ha^?1 at Ellerslie, suggesting a great potential for N loss from the soil-plant system through denitrification, and N immobilization from the soil mineral N pool. In conclusion, crop yield and N uptake were lower under zero tillage than conventional, and long-term retention of straw suggests some gradual improvement in soil productivity.     

Nitrogen fertilizer applications to maize after alfalfa: grain yield,kernel composition,and plant mineral nutrients

Nitrogen (N) is often applied to first year maize (Zea mays L.) after alfalfa (Medicago sativa L.) at rates greater than needed to attain maximum yields. This study explored other potential benefits of excess N fertilizer applications to maize after alfalfa. Effects of N fertilizer (no N fertilizer, 73, or 135 kg N ha^?1) to maize after alfalfa on stalk dry weight, stalk mineral concentrations [N, phosphorus (P), and potassium (K)], grain yield, and kernel components (protein, oil, starch, P, and K) were investigated. Fertilizer N increased stalk N concentration but not stalk dry weight. Grain yields and yields of protein, oil, starch, P, and K kernel components, expressed on a kg ha^?1 basis, were also unaffected by N fertilizer treatments. Thus, there appears to be no advantage, in terms of yield or kernel components, in applying N fertilizer to maize after alfalfa under the environments experienced during this two year field experiment.     

Molybdenum reserves of seed,and growth and N2 fixation by Phaseolus vulgaris L.

Summary Plants grown from seed with high (1.5–7.3 g Mo seed^-1) and low (0.07–1.4 g Mo seed^-1) Mo contents were grown in the presence and absence of Mo in growth media (perlite) or in a flowing-solution culture, in a controlled environment. Neither the high (1.5 g Mo seed^-1) nor the low (0.1 g Mo seed^-1) Mo content in seed from a small-seeded genotype (BAT 1297) was able to prevent Mo deficiency (reduced shoot, root and nodule dry weight, N₂ fixation and seed production) in growth media without an external supply of Mo, whereas both the high (7.3 g Mo seed^-1) and the low (0.07 g Mo seed^-1) contents in seed were able to prevent Mo deficiency in a large-seeded genotype (Canadian Wonder). Responses to Mo treatment by the Two genotypes were inconsistent between the growth media and solution culture experiments. Seed with a large Mo content (3.5 g Mo seed^-1) from the Canadian Wonder genotype was unable to prevent Mo deficiency (reduced shoot and nodule dry weight and N₂-fixation) in a solution culture without an external source of Mo, whereas both the large (1.7 g Mo seed^-1) and the small (0.13 g Mo seed^-1) contents in seed prevented a deficiency in BAT 1297. Growing plants from seed with a small Mo content, without additional Mo, reduced the seed Mo content by 83–85% and seed production by up to 38% in both genotypes. Changes in seed size and increases in shoot, root and nodule dry weight occurred, but varied with the genotype and growth conditions. These effects were also observed in some cases where plants were grown with additional Mo, demonstrating that the amount of Mo in the seed sown can influence plant nutrition irrespective of the external Mo supply. Nodule dry weight, total N content of shoots and seed production were improved by using seed with a small Mo content (1.64–3.57 g Mo seed^-1) on acid tropical soils in Northern Zambia. Plants of both the large- and small-seeded genotypes grown from seed with a small Mo content (<1.41 g Mo seed^-1) had a smaller nodule weight, accumulated less N and produced less seed. The viability of seed with a small Mo content was lower (germination up to 50% less) than that of seed with a large Mo content.     

适宜氮磷钾用量和配比提高油用牡丹产量和出油量

【目的】油用牡丹是我国新兴的木本油料作物,但施肥不平衡严重制约油用牡丹的产量和品质。研究氮、磷、钾不同施肥量和配施比例对油用牡丹产量和出油量的影响,探明油用牡丹高产、优质的适宜氮、磷、钾施用量和配比,对提高油用牡丹的生产效率具有重要的现实意义。【方法】以五年生油用牡丹品种‘凤丹’为试验材料,采用“3414”不完全正交回归设计进行了大田试验。试验地常用施肥量为尿素750kg/hm^2、重过磷酸钙270kg/hm^2、硫酸钾600kg/hm^2。设氮、磷、钾4个施肥水平为0(不施肥)、1(常用量的一半)、2(常用施肥量)、3(常用量的1.5倍)。调查了‘凤丹’产量,分析了籽粒出油量。对‘凤丹’产量进行肥效模型拟合,得出最优经济效益的氮、磷、钾肥推荐施肥量。【结果】1)施用氮、磷、钾肥可改善‘凤丹’单株果荚数、单个果荚重量、果荚直径、百粒重等农艺性状,进而提高‘凤丹’产量;氮、磷、钾肥的施用使‘凤丹’分别增产283.7、276.8和150.6kg/hm^2,增产率分别为55.5%、50.3%和23.5%,增加纯收入分别为7310.4、7494.3和2118.9元/hm^2,农学效率分别为0.96、2.76和0.59kg/kg。2)施肥增产及对产量的贡献率均表现为N>P2O5>K2O,肥料农学效率和增收效果则表现为P2O5>N>K2O,但过量施用氮、磷、钾肥会使产量有所下降,且经济效益和肥料利用效率显著降低,氮、磷、钾肥增产和增收效果以及肥料贡献率均以推荐施肥水平处理的最高,农学效率均以1水平最高。3)施用氮、磷、钾肥通过影响出仁率和种仁含油率来影响产油量,最高出仁率可达65.0%,最高种仁含油率可达32.9%,较对照组分别增加13.0%、12.6%,氮、磷、钾均衡施肥产油量可高达193.3kg/hm^2,三因素对产油量影响大小顺序为N>P2O5>K2O。4)氮、磷、钾肥之间存在明显的交互作用,配合施用能提高肥效和促进‘凤丹’的产量和种仁含油率,任一肥料的过量施用均会导致产量降低。5)使用不同拟合方法建立肥料与‘凤丹’产量效应函数方程,通过对比分析二元二次模型为最适模型,基于该最适肥效模型得出‘凤丹’氮(N)、磷(P2O5)、钾(K2O)的最优推荐施肥量为343.2、109.7、248.4kg/hm^2,适宜的氮、磷、钾施肥比例为1∶0.32∶0.72。【结论】合理的肥料配比和用量是‘凤丹’增产的保障。施用适量的氮、磷、钾肥可提高‘凤丹’农艺性状、产量、出仁率、种仁含油率等指标,进而提高产油量,氮(N)、磷(P2O5)、钾(K2O)的最优推荐施肥量为343.2、109.7、248.4kg/hm^2,适宜的氮、磷、钾施肥比例为1∶0.32∶0.72。