Tillage and nitrogen effects on growth,nitrogen content,and yield of corn

Abstract

The use of conservation tillage methods, including ridge tillage, has increased dramatically in recent years. At the present time, there is great concern that farmers are applying more nitrogen (N) fertilizer than is environmentally or economically sound. In order to determine if N requirement for optimum yield differs with tillage system, tests were initiated to study tillage and N effects on N content, soil moisture content, and yield of corn (Zea mays L.). The study was established in 1987 on two soil types, an Estelline soil (Pachic Haploboroll) and an Egan soil (Udic Haplustoll), located in eastern South Dakota. Five rates of N (0, 65, 130, 195, and 260 kg ha^?1) were applied to plots managed with 3 tillage systems: chisel plow, moldboard plow, and ridge. On the Estelline soil, in both 1988 and 1989, ridge‐tilled plots contained a greater amount of water in the soil profile at emergence and at mid silk than did plots in the other two tillage systems. Soil moisture content at mid silk was significantly correlated with earleaf N, total N uptake, and grain yield in 1988 and earleaf N and grain yield in 1989. However, the correlation coefficients were higher in 1988 than in 1989. On the Egan soil, there were no significant differences in soil moisture content among tillage systems. On the Estelline soil, corn grain yield was affected by a tillage x N‐rate interaction in 1988. Maximum yield within the ridge system was achieved with the 130 kg ha^?1 rate. In 1989 on the Estelline soil, yield was affected by tillage and N rate, but there was no interaction between factors. When averaged over N rates, yields were 7.1, 6.6, and 6.5 Mg ha^?1 in the ridge, moldboard, and chisel systems, respectively. In 1988 plant total N uptake was greater in the ridge system than the moldboard or chisel systems; in 1989 uptake was affected by N rate alone. On the Egan soil, tillage did not affect soil moisture, total N uptake or grain yield in either year. Corn grain yield increased with increasing N rate up to the 195 kg ha^?1 rate. This study indicates that, on some soil types, ridge tillage can improve soil water holding capacity, N utilization and yield of corn.     

Sewage sludge effects on soybean growth and nitrogen fixation

The effect of sewage sludge application, as a source of phosphorus, on dinitrogen symbiotic fixation in soybean was evaluated. The experiment was carried out in a greenhouse and included eight different treatments: (1) no fertilization, (2) complete fertilization, (3) inoculation with rhizobia plus phosphate fertilization (IS+P), (4) inoculation with rhizobia without phosphate fertilization (IS-P), (5) inoculation plus dose 1 of sewage sludge (IS+SS1), (6) inoculation plus dose 2 of sewage sludge (IS+SS2), (7) without inoculation plus dose 1 of sewage sludge, and (8) without inoculation plus dose 2 of sewage sludge. The two rates of sewage amendment corresponded to 11.2 t ha^-1 and 22.4 t ha^-1 and were calculated on the basis of the sewage phosphorus content and the amount of phosphorus recommended for soybean fertilization. Results were evaluated 49 and 63 days after plant emergence. Nodule number and weight decreased as follows: IS+P>IS+SS1, IS+SS2>IS-P. No nodules were formed without inoculation. The acetylene reduction activity was highest for the IS+P treatment 49 days after plant emergence. At the 63-day harvest that parameter was similar among IS+P, IS+SS1 and IS+SS2 treatments. The total amounts of nitrogen in shoots were similar for IS+P, IS+SS1 and IS+SS2 treatments at the first harvest but by 63 days after plant emergence, total amounts of nitrogen in above-ground parts (shoot and pods) were higher in IS+P and IS+SS2. This was due to higher pod dry weights. This study demonstrated that soybean growth can be improved by sewage sludge at a low application rate without the necessity of additional phosphorus fertilization.     

Phosphorus source effects on alfalfa yield,total nitrogen content,and soil test phosphorus

Abstract

Recent studies showing a lack of response by alfalfa (Medicago sativa L.) to phosphorus (P) fertilization have raised concerns about the efficacy of commonly used P fertilizer materials in the southwestern United States. Studies were conducted between 1982 and 1985 in southeastern New Mexico to evaluate (i) alfalfa yield response to different P sources, (ii) the effect of P fertilizer source on forage total nitrogen (N) content and leafiness, and (iii) the effect of P fertilizer source on soil test P. Nine P sources were applied annually from 1982 through 1984 at a rate of 58 kg P/ha. Alfalfa was grown during 1985 without fertilization to examine the residual effect of P sources. Triple superphosphate (TSP) and monoammonium phosphate (MAP) gave the highest alfalfa forage yields over the 3‐year application period, but no residual fertilizer effects were observed when fertilization was discontinued. Fertilization did not affect forage leafiness. Except for a small N response in forage total N content in 1984, neither P nor concomitant applied N had a significant effect on forage N content over the 3‐year period. Phosphorus fertilization significantly increased average soil test P for the 3‐year period, but there were no significant differences between treatments. Currently used P materials (TSP and MAP) still appear to be the most efficacious for alfalfa production.     

Glyphosate- and imazethapyr-induced effects on yield, nodule mass and biological nitrogen fixation in field-grown glyphosate-resistant soybean

Over half of the 21 Mha of soybean planted in Brazil is now transgenic glyphosate-resistant (GM_RR). A field experiment was carried out to investigate whether the application of glyphosate or imazethapyr to the GM_RR variety reduced the input of N₂ fixation (BNF). No effects on yield, total N accumulation, nodulation and BNF (δ¹⁵N) could be assigned to the genetic modification of the plant. Imazethapyr reduced soybean yield but had no significant effect on BNF. Even though yields were not affected by glyphosate, the significant reduction of nodule mass and BNF to the GM_RR suggests that the use of this herbicide could lead to an increased dependence on soil N and consequently an eventual decrease of SOM reserves.     

Effect of nitrogen application on seed yield,pod and seed characteristics of okra

Four okra cultivars [Abelmoschus esculentus (L.) Moench] were cultivated for two growing periods at nitrogen (N) application rates of 150, 300 and 450 mg N L^?1. There was no effect of N on pod size (length and diameter) or on the number of seeds per pod and seed size (mean 1000 seed weight), all these characteristics of which related to the genotype. High N application (450 mg N L^?1), increased the seed yield of the cultivar with the lowest flower induction (Boyiatiou), but only in experiment 2. In Veloudo, seed yield was highest at 300 mg N L^?1, whereas in Pylaias and Clemson 450 mg N L^?1 reduced seed yield. In all cultivars, seeds produced at an N rate of 450 mg N L^?1 exhibited a significantly higher percent germination N, possibly by reducing the incidence of seed hardness.     

不同磷肥水平对大豆磷营养状况和产量品质性状的影响

本试验选用近年来黑龙江省推广面积较大并具有代表性的3个基因型大豆品种作为试验材料,采用盆栽试验,利用钼锑抗比色法测定了大豆生育期各器官磷素含量,并测定了单株产量及成熟子粒蛋白质和脂肪含量,结果表明:施磷量对不同大豆品种植株及各器官磷素含量有较大影响;不同品种不同处理全株及各器官磷素含量从分枝期逐渐增加,开花期达到高峰,随后下降至成熟期;同一品种不同处理间高蛋白品种和中间型品种是P150处理全株磷积累量最高,高油品种是P225处理全株磷素积累最高;生育期内只有适宜施磷才能促进磷素含量达到最高峰;同一处理不同品种间是高油品种磷素积累量大于中间型品种和高蛋白品种,说明高油品种需磷量多于中间型品种和高蛋白品种。高蛋白品种和中间型品种P150处理单株产量和子粒蛋白质含量最高,高油品种P75处理单株产量和子粒蛋白质含量最高。3个品种脂肪含量均以P225处理最高。     

氮肥对大豆结瘤固氮、籽粒产量和蛋白质含量的影响

【目的】合理施用氮肥不仅可提高大豆结瘤固氮能力,还可减少农业污染,实现大豆生产的高产优质高效。研究施氮时期和施氮量对大豆结瘤固氮、产量及蛋白质含量的影响,为大豆高产优质提供理论基础及科学依据。【方法】采用盆栽试验,供试大豆品种为‘东生35’,试验设2个氮肥施用时期(V2期和R1期)和3个氮肥施用量[N 0、5、100 mg/(kg,土)],表示为N0、N5和N100。在大豆R2期(盛花期)和R5期(鼓粒期)取样分析了地上部干物质积累量、根瘤数量、根瘤干重和固氮酶活性。在R8期(成熟期)调查了大豆籽粒产量和蛋白质含量。【结果】施氮时期和施氮量对大豆地上干物质积累、结瘤和固氮能力均有显著影响。不论是V2期还是R1期施氮,大豆地上部干物质积累量均随着施氮量的增加而增加,而根瘤干重、数量则呈降低的趋势。R1期施氮条件下,N100处理的大豆盛花期根瘤数量和根瘤干重比N0分别下降了42.3%和32.8%,而固氮酶活性则均以N5处理最高;V2期施氮条件下,N5处理的大豆固氮酶活性在R2期和R5期较N0处理分别增加15.3%和27.1%。大豆籽粒产量和蛋白质含量均以N5处理最高,籽粒蛋白质含量较N0处...     

东北黑土区大豆生长、结瘤及产量对氮、磷的响应

氮肥和磷肥显著影响大豆的结瘤和产量。然而在土壤肥力较高、速效养分有效性差的东北地区,有关氮肥和磷肥施用量对大豆结瘤和产量影响的研究较少。本试验采用裂区田间试验,设置3个氮（N）水平（0、20 和 50 kg/hm2）和 3 个磷（P）水平（0、 20 和 40 kg/hm2）,研究氮、 磷及其交互作用对大豆生长发育、 结瘤特征及产量的影响。结果表明, 单施氮肥大豆生物量和产量随着施氮量的增加而增加,而根瘤数量、 干重、 大小和结瘤指数呈逐渐下降的趋势。单施磷肥促进大豆生物量、 产量、 根瘤数量、 干重、 大小和结瘤指数的增加,但其增幅低于施氮处理下的增幅。氮磷对大豆生长和产量促进作用高于单施氮和单施磷处理,但差异不显著;氮磷处理下的根瘤数量、 干重、 大小和结瘤指数低于单施磷处理;氮磷处理下N2（N 50 kg/hm2）处理下的大豆根瘤数量、 干重、 大小和结瘤指数高于N1处理（N 20 kg/hm2）下的,随着施磷量的增加大豆根瘤数量、 干重、 大小和结瘤指数增加,施磷能够抵消氮对大豆根瘤产生和形成的抑制。氮、 磷及其交互作用对大豆根瘤的影响都是直接的,并且不是通过促进大豆生长间接促进的。因此氮和磷均是限制东北地区大豆结瘤和产量的因素,但氮是主导因素。若要获得大豆高产,氮肥施用量需要控制在50 kg/hm2,磷肥在40 kg/hm2;但若想最大的发挥大豆的结瘤固氮功能,那么应该不施或者减少氮肥的施用量到20 kg/hm2,磷肥仍在40 kg/hm2。     

Plant density and nitrogen effects on growth dynamics,light interception and yield of maize

Maize (Zea mays L.) growth and yield are most sensitive to variations in plant density and nitrogen (N) in north-western Pakistan. This study was conducted on the Agricultural Research Farm of NWFP (North West Frontier Province) Agricultural University, Peshawar, from 2002–2004 to establish an accurate plant density and N management system aimed at high yield of maize. The 2 × 3 × 6 factorial experiment was designed having two plant densities (P1 = 60,000 and P2 = 100,000 plants ha^?1) and three nitrogen rates (N1 = 60, N2 = 120 and N3 = 180 kg N ha^?1) applied to the main plots, while six split application for N in different proportions were applied to subplots at different growth stages of maize in two equal (S1), three equal (S2), three unequal (S3), four equal (S4), five equal (S5) and five unequal splits (S6) at sowing and with 1st, 2nd, 3rd and 4th irrigation at two-week intervals. Growth rate and yield increased with elevated dose and number of N split applications. Improved endurance to high stands allowed maize to intercept and use solar radiation more efficiently, contributing to the remarkable increase in the crop growth rate and yield.     

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 soil ph,nitrogen source,phosphorus, and molybdenum on early growth and mineral nutrition of burley tobacco

Abstract

Previous research has indicated that P application may influence plant Mo nutrition, and that both P and Mo are influenced by soil pH. This is of interest, since Mo is deficient in some soils and because large quantities of acidifying nitrogenous fertilizers are commonly applied in production of burley tobacco (Nicotiana tabacum L.).

Burley tobacco was grown in two experiments using Maury silt loam soil (Typic Paleudalfs) to determine the influence of soil acidity, form of N applied, and P application on plant growth and mineral nutrition. The studies were conducted in the greenhouse so that high root densities would develop and the data primarily reflect rhizosphere effects.

Ammonium application depressed rhizosphere pH 0.4 to 0.6 pH units. Nitrate nutrition raised soil pH less than 0.1 pH unit. Plants supplied NH₄ exhibited slower early growth than plants supplied NO₃. Several significant interactions involving soil pH, N source, P, and Mo occurred. In the first experiment, plant P was not affected by form of N applied, while in the second experiment NH₄ application resulted in higher plant P concentration, both in presence and absence of applied P. Application of NH₄ also increased plant weight in the second experiment. Plant P concentration was influenced by pH, being greatest at pH 6.2 and decreasing as pH levels decreased or increased. Plant Mo concentration did not differ among forms of N at pH 5.4, but at pH 7.2 was three times greater in the presence of NO₃. When Mo was applied, P addition enhanced plant Mo concentration, but when Mo was not applied, P addition did not increase Mo concentration. This effect of P on Mo occurred only in the presence of N and was greater in the presence of NH₄ than NO₃. These observations suggest that enhancement of plant Mo nutrition by P application may be dependent on adequate levels of N being present.     

水氮联合调控对小油菜生长、产量及品质的影响

采用温室盆栽试验,研究了水氮联合调控对小油菜生长、产量及品质的影响。结果表明,灌水水平与施氮量对叶片数、叶面积、叶绿素与产量均有显著或极显著影响,这些指标均随灌水水平的提高而增加,随施氮量的增加呈抛物线趋势,在低氮(0.1 g·kg~(-1))与中氮处理(0.2 g·kg~(-1))达到最大,且差异不显著。中水高氮(田间持水量的75%,0.3 g·kg~(-1))耦合能显著提高小油菜Vc含量;灌水、施氮及其交互作用对可溶性糖与硝酸盐含量影响极显著;增加灌水能减轻高量氮肥对小油菜可溶性糖合成的抑制作用;不施氮处理硝酸盐含量均极显著低于施氮处理,高水低氮(田间持水量的90%,0.1 g·kg~(-1))与中水(田间持水量的75%)下的各个施氮处理硝酸盐含量较低。降低施氮量,适当增加灌水能增加Vc、可溶性糖含量,降低硝酸盐积累。综合考虑小油菜生长、产量及品质,中水低氮(田间持水量的75%,0.1 g·kg~(-1))为最佳水氮处理。     

Effects of deep placement of controlled-release nitrogen fertilizer on soybean growth and yield under sulfur deficiency

Sulfur (S) and Nitrogen (N) metabolisms in plants are interacted and it is known that S deficiency decrease N absorption and metabolism. In leguminous plants S deficiency also decreases N₂ fixation by rhizobia in the nodules. Deep placement of a controlled-release N fertilizer is a good method to provide nitrogen to soybean without inhibiting N₂ fixation; thus, it was hypothesized that this method is able to provide nitrogen effectively to sulfur-deficient soybean plants. In this study effects of deep placement of coated urea on S-N physicological interaction, growth and productivity in soybean plants were examined using pot experiments. Soybean plants were grown with sulfate concentrations of 30, 100, or 1000 μM, with or without deep placement of coated urea. Shoot weights at the developing stage were not affected by S deficiency. SPAD values of leaves during the flowering stage decreased with S deficiency and increased with the deep placement of coated urea. S deficiency decreased seed weight per plant at the harvesting stage, but this decrease was attenuated by the deep placement of coated urea. N and S content in shoots at the developing stage increased with the deep placement of coated urea, whereas in seeds, only the N content increased. N₂ fixation activity based on the relative ureide-N content in xylem sap indicated that the deep placement of coated urea did not inhibit N₂ fixation activity at the early flowering stage. Without deep placement of coated urea, the relative ureide-N content decreased under S deficiency at the seed filling stage. These results suggest that the deep placement of coated urea is an efficient method to supply N to support soybean yield under S deficiency.

Abbreviations: Deep+: with deep placement of coated urea; Deep–: without deep placement of coated urea     

不同施氮水平对加工番茄养分吸收、分配及产量的影响

根据供试土壤的养分状况,通过2年不同施氮水平的田间小区试验,2007年设施N 0、135、270、405 kg/hm2四个水平,2008年设施N0、150、300、450 kg/hm2四个水平,在加工番茄的主要生育期,测定植株生物量和不同器官氮、磷、钾含量,并结合成熟期产量,研究不同施氮水平对加工番茄养分吸收、分配及产量的影响。结果表明,加工番茄对氮、钾需求量远大于磷;加工番茄干物质及氮、磷、钾养分的积累动态均呈"S"型增长;施氮可以极大地促进加工番茄植株对氮、磷、钾的吸收,各施氮处理比不施氮处理多吸收氮75.8%～189.2%,多吸收磷49.4%～162.7%,多吸收钾60.7%～176.8%;在一定的施氮范围内,吸收氮、磷、钾的量随施氮量增加而增加;植株吸收的养分最终50%以上都聚集在果实中;在施用磷、钾肥的基础上合理施用氮肥可以显著提高加工番茄的经济产量,2007和2008年增产分别达43.8%和114.3%;过量施氮可造成加工番茄贪青晚熟,但可以通过后期合理增施氮肥,作为解决加工番茄采收期短、加工紧张问题的一个辅助措施。     

小麦/玉米/大豆间套作体系中小麦施磷后效对大豆产量、营养状况的影响

为评估磷肥的施用后效,在田间试验条件下研究了四川小麦/玉米/大豆周年间套作体系中小麦施磷对后作大豆产量及营养状况的影响。结果表明,在小麦5个磷（P2O5）处理（0、 45、 90、 135、 180 kg/hm2）后,大豆播前土壤有效磷分别为19、 22、 51、 57、 62 mg/kg（记为SP0、 SP1、 SP2、 SP3、 SP4）,大豆籽粒产量随土壤有效磷含量的增加呈先增加后减少的趋势,SP1的籽粒产量最高（1797 kg/hm2）,较SP0增加116%,而SP2SP4的大豆产量只比SP0增加了4.3%~4.7%,SP1~SP4间无显著差异;大豆茎产量随土壤有效磷含量的增加而增加,SP1、 SP2、 SP3、 SP4比SP0分别增加10.4%、 22.4%、 28.5%、 31.5%。随着土壤有效磷的增加,大豆总荚数和饱荚数有随之增大的趋势,总荚数在SP4处理最大,比SP0增加11.1%,饱荚数在SP1最大,比SP0增加13.9%,而瘪荚数是先显著减少后又逐渐增大（SP1最小为8.8荚/株,SP4最大为13.4荚/株）,饱瘪比是先显著增大后又逐渐减少（SP1最大为8.50,SP0最小为5.06）。大豆籽粒、 茎的氮、 磷含量随土壤有效磷含量的增加呈先增加后降低的趋势,都在SP2时达最大（籽粒氮、 磷含量7.718%、 0.764%; 茎氮、 磷含量0.659%、 0.065%）,而钾含量随土壤有效磷的增加而增加。大豆茎生物量,磷、 钾养分含量和氮、 磷、 钾养分积累量与土壤有效磷含量呈极显著正相关。SP2、 SP3、 SP4 3个处理大豆吸磷量分别是SP0的1.7、 1.6、 1.7倍,而其生物量仅为SP0的1.2、 1.3、 1.3倍。综上,适宜的土壤磷有利于大豆的生长,土壤磷过高反而可能造成大豆植株的徒长而影响结荚和鼓粒,在小麦/玉米/大豆体系中后作大豆可不施或少施磷,充分利用前作小麦施用的磷肥以提高磷肥的利用率。     

Fertilization effects on soybean growth and yield in the southern guinea savanna of nigeria 1

Soybean production is increasing in savanna regions of West Africa. However, only limited information exists concerning nutrient requirements of soybean in the region. Trials were conducted at five locations in the Southern Guinea Savanna of Nigeria to determine the response of soybean [Glycine max (L.) Merr.] to P, K, and to a combination of secondary elements and micronutrients. Responses to P varied with P status of the soil and with the application of supplemental secondary elements and micronutrients. Fertilization with K had no effect on yield. Fertilization with secondary elements and micronutrients increased grain yield at all sites after severe P deficiencies were eliminated. Mineral analyses of leaf tissue suggested deficiencies in several secondary elements and micronutrients as well as the possibility of Mn toxicity.     

Effect of manganese deficiency on seed yield of soybean cultivars

Manganese (Mn) deficiency is a problem in soybeans grown on high pH soils, which to date can only be controlled by chemical fertilizers. In view of the success of genetic resistance in reducing yield losses associated with iron (Fe) deficiency chlorosis, a one year study was initiated to determine whether genetic resistance could be used to control Mn deficiency related yield losses. For this study, twenty soybean genotypes ranging from Group I maturity to Group III maturity were planted at five locations which had previously exhibited symptoms of Mn deficiency. Individual plots were rated for Mn‐deficiency symptoms on a 1–5 scale (1 = no yellowing to 5 = severe yellowing with some necrosis) at the Rl growth stage and plants in the center rows were harvested for yield. The mean Mn‐deficiency rating was 2.8 with a range from 1.8 for NKS 23–03 and P9181 to a 3.9 for A3205. The mean yield was 3059.3 kg/ha with a range from 3670.6 for A3205 to 2567.5 kg/ha for Chapman. The correlation between Mn‐deficiency rating and yield was not significant presumably due to the high yields of some of the later maturing cultivars.     

Effects of phosphorus nutrition on growth,fruit abscission and seed yield of the cowpea (Vigna unguiculata L.)

In pot experiments, cowpea cultivars, ?Adzuki”?, ?Ife Brown”? and ?New Era”?, were raised in soil fertilized with phosphorus at 0, 20, 40 and 80 kg/ha levels. Seed yield was enhanced in ?Adzuki”? mainly by the maintenance of functional pods, that ist by enhancement of fertility (defined as percent of floral buds that developed into mature functional, seed-bearing pods). In ?New Era”?, seed yield increase was due more to increased diversion of dry matter into the seed than by increased fertility. Harvest index (defined as the proportion of whole plant dry weight constituted by seed dry weight) was significantly enhanced more in ?New Era”? than in ?Adzuki”?. A P dressing equivalent to 40kg P/ha proved the nearest-optimal P level for seed production in ?New Era”?. Corresponding critical P level for ?Adzuki”? and ?Ife Brown”? were not specifically at any of the P regimes studied.     

氮素营养水平对大豆氮素积累及产量的影响

以“东农47”为试材,采用15N 标记的 (NH4)2SO4作为氮源,利用砂培方式研究了氮素营养水平对大豆氮素积累及产量的影响。结果表明,随外源氮水平增加,大豆植株氮素积累量和产量呈先增加后降低的变化趋势,当营养液氮浓度为50 mg/L时,植株氮素积累量和子粒产量最大。在 R4和 R5 期补充氮肥的供给明显增加植株对氮的积累,并能显著提高大豆产量。大豆生长需要一定量的“启动氮”,“启动氮”的作用维持到V3期对大豆氮的积累和产量形成效果最好。随外源氮水平增加,大豆吸收外源氮的比例增加,根瘤固氮所占比例降低,外源氮和根瘤固氮积累量随外源氮水平增加呈先增加后降低的变化趋势。当氮浓度为100 mg/L时,有利于植株对外源氮的吸收,当氮浓度为50 mg/L时,有利于根瘤固氮的积累,“启动氮”的作用维持到V3期根瘤固氮的积累明显增加; 在R4和R5期补充外源氮的供给可以显著增加对外源氮利用,以R5期效果最好。     

Effect of sulfur source and rates on yield and yield components of soybean in subtropical soils

Abstract

The supply of sulfur (S) fertilizers, such as phosphogypsum, to new agricultural frontiers has been hindered by the high cost of freight. However, this problem could be resolved by utilizing deposits of rock in the affected regions. Accordingly, a greenhouse study was designed to evaluate the effect of S source and rate on soybean yield. Five S rates (0, 50, 100, and 200?mg kg^?1) and five S sources (S-phosphogypsum, S-Niquelândia rock, S-Araripina rock, S-Grajaú rock, and S-Sulfurgran [90% S0?+?10% bentonite]) were applied to soybean grown in two soil types (Typic Ultisol and Typic Oxisol), which differ in clay content. Regardless of soil type, the application of P-phosphogypsum resulted in a higher grain yield. However, application of the other S sources also improved grain yield as well as total dry weight; S application, in general, improved soybean yield components (number of grains per pod, number of pods per pot, and weight of pods per pot), photosynthetic rate, chlorophyll content, and the S levels of leaves and grains as well as the available sulfate (SO₄^2-) levels in the soil. Therefore, for soybean grown in Typic Ultisol and Typic Oxisol, different S sources effectively improve a variety of variables that ultimately improve grain yield.