Rooting pattern and nitrogen uptake of three cauliflower (Brassica oleracea var. botrytis) F1‐hybrids

In a two‐year field trial at the sites Ruthe (Germany, loess soil, Orthic Luvisol) and Schermer (The Netherlands, marine clay soil, Eutric Fluvisol) the cauliflower F₁‐hybrids Marine, Lindurian and Linford were compared in their efficiency of N use from limiting and optimum supplies of N. Limiting N was N_min at planting. Optimum N was 250 kg ha^—1 as the sum of inorganic N content of the soil (N_min) at planting and fertilizer‐N. Marine was the most efficient variety, producing the highest shoot dry‐matter and quality (% class 1 curds) at both limiting and optimum N supplies. The N supply did not affect the horizontal and vertical distribution of root length density per soil volume (RLD, cm cm^—3) irrespective of variety. The RLD decreased exponentially with increasing soil depth. Varietal differences in RLD were not found at Ruthe, whereas at Schermer Marine had the highest RLD in all soil layers investigated (0 to 60 cm). No correlations were found between RLD and residual N_min at harvest, except at limiting N supply in Schermer where a strong negative correlation was found between RLD in the 45 to 60 cm layer and N_min at harvest. Thus, varietal differences in N efficiency are speculated to be rather due to different internal N‐use efficiency than to differences in N‐uptake efficiency.     

灌溉模式和有机肥配施对水稻产量、光合特性和氮肥利用率的影响

针对湘北地区农业水资源日益紧缺和水稻生产上滥施化学氮肥的现状，为了节约淡水资源、降低化肥用量、实现水肥协同和资源高效利用，设置2种灌溉方式(W₁：全生育期淹水灌溉；W₂：全生育期湿润灌溉)和4个施氮水平(N₀：不施氮肥；N₁：施N量150 kg/hm²，肥料为尿素氮100%；N₂：施N量150 kg/hm²，肥料为尿素氮80%+有机氮(菜枯)20%；N₃：施N量150 kg/hm²，肥料为尿素氮60%+有机氮(菜枯)40%)，分析水稻产量、光合特性、氮素代谢和氮肥利用率对灌溉模式和有机肥配施的响应规律。结果表明：与W₁相比，W₂显著增加水稻产量、氮肥利用率、净光合速率、蒸腾速率、气孔导度等；在不同施氮处理下，增加有机肥比例能显著提高产量，N₃、N₂、N₁分别比N₀增产28.32%、25.52%、18.88%，同时氮肥吸收利用率、氮肥农学利用率和氮肥偏生产力也表现为N₃>N₂>N₁，N₃的氮肥吸收利用率、氮肥农学利用率、氮肥偏生产力分别达到了78.52%、9.77 kg/kg、46.91 kg/kg。综合评分法表明，灌溉模式和有机肥配施的最佳模式为W₂N₃，即湿润灌溉、施N量150 kg/hm²、肥料为尿素氮60%+有机氮(菜枯)40% 组合。该研究结果可为湘北地区水稻水肥管理提供科学依据。     

新疆膜下滴灌棉花早衰的根系生长发育特征

【目的】 膜下滴灌 (drip irrigation under mulch film, DI) 技术由于其高效节水的特点在新疆大面积推广使用,然而近期发现应用滴灌技术进行灌溉的作物根系出现了早衰,影响了地上部生长及产量的形成。本研究探讨了目前膜下滴灌技术体系棉花根系生长发育、空间分布的动态变化规律及地上部响应。 【方法】 采用田间试验方法,设置膜下滴灌、漫灌 (flood irrigation under mulch film, FI,对照) 两处理,采用 Monolith 法分 7 次采集根系,DT-Scan 软件测定根系长度,分析不同生育时期棉花根系在土壤空间中的变化特征,同时采集地上部样品并分器官测定干物质量。 【结果】 滴灌棉花根系表现出明显的浅层分布趋势:从播种后 96 d 开始,距地表 10 cm 范围内的根系长度明显大于漫灌处理,而 30—60 cm 土层则正好相反;在播种后 65～96 d 内,滴灌棉花根长增加速率明显低于漫灌;棉花生长发育后期 (播种后 125～160 d),滴灌处理棉花根系显著衰退,且主要集中在 0—40 cm 深度、距滴灌带 30—70 cm 土体范围内,播种后 160 d 与 125 d 相比,0—10 cm 土层下降了 13.8%,而 10—40 cm 衰退幅度更大 (22%),与此同时,漫灌处理除 0—10 cm 土层根长有所下降外 (7.7%),10 cm 以下依然保持增长状态 (10—40 cm 及 40—60 cm 层分别增加了 5.5% 与 10.2%);播种后 125 d,滴灌棉花地上部生长量明显高于漫灌,而根系正好相反,其冠根比较漫灌高,而在播种后 160 d 剧烈下降 (地上部叶片及蕾、铃的大量脱落所致 )。 【结论】 膜下滴灌棉花根系由于浅层分布,根系体积小,而地上部生物量过大,导致其在生长发育后期快速衰退。今后应研究适宜的水肥调控措施,以构建更早、更深的根系系统,控制生殖生长期内棉花的营养生长,实现膜下滴灌棉花的高产稳产。      

灌溉和施氮对河西走廊紫花苜蓿生物量分配与 水分利用效率的影响

确定河西地区紫花苜蓿栽培草地的合理施氮量和灌溉量,对优化当地紫花苜蓿栽培草地生物量分配和提高水分利用效率具有重要意义。本研究利用田间试验研究了不同灌溉量(W1:当地灌溉量的60%;W2:当地灌溉量的80%;W3:当地灌溉量1 920 m3·hm-2)和施氮量[N1:0 kg(N)·hm-2;N2:40 kg(N)·hm-2;N3:80 kg(N)·hm-2;N4:120 kg(N)·hm-2]对2年生紫花苜蓿生物量分配特征及水分利用效率的影响。结果表明:灌溉量为W2和W3时均显著增加了紫花苜蓿株高、单株分枝数、地上生物量,及20~40 cm、40~60 cm和0~60 cm土层的根系体积、根系生物量和水分利用效率,且W2和W3的紫花苜蓿株高、单株分枝数和地上生物量差异不明显,说明采用当地灌溉量的80%水量时,紫花苜蓿水分利用效率最高。随着施氮量增加,紫花苜蓿单株分枝数、叶茎比、根系体积、根系生物量、地上和地下生物量比和水分利用效率均呈现先增加后降低的趋势,且在施氮量为80 kg(N)·hm-2时最大,说明紫花苜蓿根系发育和水分利用效率对氮的响应均存在剂量效应。在水氮互作条件下,处理W2N2或W2N3中紫花苜蓿株高、单株分枝数、根系体积和0~20 cm、20~40 cm、0~60 cm根系生物量及地上生物量与地下生物量比值和水分利用效率达到最优。结合上述分析得出在灌溉量W2和施氮N3时,紫花苜蓿地上地下生物量比值和水分利用效率达最大值,表明河西走廊紫花苜蓿栽培草地的适宜灌溉量为当地灌溉的80%,施氮量为80 kg·hm-2,此时紫花苜蓿水分利用效率和地上地下生物量比值配置最优。     

灌水施氮和缩节胺用量对南疆棉花产量品质和水肥利用效率的影响

为研究灌水量、施氮量和缩节胺用量对棉花籽棉产量、纤维品质和水肥利用效率的交互影响,于2020年和2021年在南疆库尔勒地区开展大田试验,设置3个灌水量（W₁：60%ET_c,W₂：80% ET_c,W₃：100% ET_c,ET_c为作物蒸发蒸腾量）,4个施氮量（N₀：0 kg/hm²,N₂₀₀：200 kg/hm²,N₃₀₀：300 kg/hm²,N₄₀₀：400 kg/hm²）和2个缩节胺用量（D₁：120 g/hm²,D₂：240 g/hm²）。结果表明：灌水量、施氮量和缩节胺用量对籽棉产量、水分利用效率、肥料偏生产力和部分纤维品质指标影响显著（P<0.05）。灌水量、施氮量和缩节胺用量三者交互作用对肥料偏生产力和纤维品质影响显著（P<0.05）。株高、叶面积指数和干物质量也受灌水量、施氮量和缩节胺用量三者交互作用影响。W₃N₃₀₀D₂处理籽棉产量最高（2020年为7 578 kg/hm²,2021年为7 173 kg/hm²）,W₁N₄₀₀D₁处理水分利用效率和W₃N₀D₂处理肥料偏生产力最高,W₃N₄₀₀D₁处理的纤维长度、纤维强度和马克隆值均获得较大值,纤维品质最佳。基于TOPSIS综合评价方法对棉花产量品质和水肥利用效率进行综合评价,100%ET_c灌水量、300 kg/hm²施氮量和240 g/hm²缩节胺用量组合最优,可作为南疆棉花适宜的水氮和化控管理模式。研究结果可为南疆棉花水肥高效利用提供理论依据和科学指导。     

Partial replacement of chemical fertilizer by manure affects maize root traits in North China Plain

In order to achieve high yields and environmental friendliness simultaneously, the replacement of chemical fertilizers by manure has become a research hotspot in recent years. Roots absorb nitrogen, participate in its assimilation and contribute to the cereal's dry matter accumulation. A 5-year filed experiment in the North China Plain was initiated to assess the response of root morphology and distribution of summer maize (Zea mays L.) to fertilizer application and contribution to crop yield. The treatments included CK (unfertilized control), NPK (inorganic nitrogen/phosphorus/potassium fertilizer) and NPKM (manure + 70% NPK). We determined the root biomass, root diameter, root length density (RLD) of three diameters (>0.8 mm, 1stRLD; 0.2–0.8 mm, 2ndRLD; <0.2 mm, 3rdRLD) and the soil chemical properties at 60 cm with 10 cm increments. At 40–60 cm, NPKM significantly decreased the root diameter than NPK. Fertilization showed no effect on total RLD, 1stRLD, 2ndRLD and 3rdRLD for a 60-cm soil profile. At 40–50 cm, the NPKM increased the RLD compared to NPK, mainly by increasing the 2ndRLD and 3rdRLD. Under CK and NPK, root lengths of 0–20 cm made up 62% and 57% of the total root length, respectively. Under NPKM, root lengths of 40–60 cm made up 46% of the total root length. Our results indicate that maize yield was preserved after replacing 30% of N fertilizer with manure, presumably depending on the change of root vertical distribution pattern and increase of the fine root length in deeper soil.     

灌溉方式与秸秆覆盖优化施氮模式对秸秆腐熟特征及水稻氮素利用的影响

以杂交籼稻‘F优498’为试验材料,研究不同灌溉方式[淹水灌溉(CK)、干湿交替灌溉、旱作]下氮肥运筹与秸秆覆盖优化管理模式(麦秆覆盖优化施氮模式、油菜秆覆盖优化施氮模式以及无秸秆覆盖优化施氮模式)对水稻根系生长、各时期氮素积累以及产量的影响,探讨各灌溉方式下秸秆腐熟及氮素释放规律,明确秸秆腐熟与氮素释放规律对水稻生长的影响及其相关关系。结果表明,淹水灌溉和干湿交替灌溉均较旱作有效地协调各时期水稻地上部、地下部生长,促进各时期氮素吸收利用,提高稻谷产量;而水分生产效率则以旱作为最优,干湿交替灌溉次之,但差异不显著。麦秆、油菜秆的腐熟与氮素释放效率最高峰均出现在移栽后30 d,但腐熟量与氮素释放量受灌溉方式与秸秆种类的影响;油菜秆腐熟量显著高于麦秆,旱作明显高于干湿交替与淹水灌溉;氮素释放量则以麦秆为最优。秸秆覆盖优化管理模式也对水稻各生长指标具有显著影响;淹水及干湿交替灌溉下,麦秆覆盖氮肥运筹优化管理模式有效协调水稻植株各时期的生长,促进氮素吸收利用,最终实现产量的增加;油菜秆覆盖氮肥运筹优化管理模式则在整个生育期均对水稻生长表现轻微抑制效应;而旱作模式下麦秆、油菜秆优化施氮模式覆盖均呈现显著的促进作用,其中油菜秆覆盖优势明显,可作为生产中水资源不足的情况下参考。秸秆腐熟量及氮素释放量与水稻根干重、氮素吸收利用以及产量的相关性分析表明,移栽后30 d秸秆腐熟量与稻谷产量、氮素吸收均呈显著的负相关关系(r=?0.27*~?0.29*),而齐穗期、成熟期氮素释放量与产量及氮素吸收均呈显著的正相关关系(r=0.31*~0.59**);同时,秸秆的腐熟量与氮素释放对水稻根冠比影响较大,其中以齐穗期最为显著(r=?0.27*~0.42**)。协调水稻各时期秸秆腐熟量及氮素释放,特别是移栽后30 d氮素释放量是保证实现水稻高产、高效的重要措施之一。     

Compatibility of root growth and tuber production of potato cultivars with dynamic and static water‐saving irrigation managements

The important root characteristics of root length density (RLD) and root mass density (RMD) generally differ among irrigation managements and potato cultivars. The objective of this study was to investigate the RLD and RMD variations and their functional relationships with gross potato tuber yield for two commercial potato cultivars, Agria and Sante, under different irrigation strategies. Full irrigation and water‐saving irrigation strategies, deficit and partial root drying irrigations, were applied statically (S) and dynamically (D) based on daily crop evapotranspiration. Results showed that SPRD had significantly greater RLD (3.64 cm/cm³) and RMD (132.7 μg/cm³) than other irrigation treatments. Between the potato cultivars, Agria had significantly larger values of RLD (3.50 cm/cm³) and RMD (138.7 μg/cm³) than Sante. The functional relationship between the root growth characteristics and tuber yield showed that under water‐saving irrigations, Agria increased root mass at the expense of gross tuber yield but Sante increased root mass to maintain larger gross tuber yields. However, Agria produced more roots and gross tuber yield than Sante, and it is concluded that Agria is a more drought‐tolerant potato cultivar, which is recommended for tuber production in regions where water might be scarce. It was shown that larger root production in potatoes was associated with improved tolerance to water stress.     

Fertilizer location modifies root zone salinity,root morphology,and water‐stress resistance of tree seedlings according to the watering regime in a dryland reforestation

There is a direct relationship between soil nutrient concentration in localized zones and root proliferation and elongation under well‐watered conditions. However, in field studies under semiarid conditions this relationship can change due to higher salt accumulation and soil dryness that affect root growth, water stress resistance, and seedling survival. We assessed the effect of different locations of fertilizer placement in the soil profile and water availability on root zone salinity, root development and ecophysiological responses of Quillaja saponaria Mol. after outplanting. A single dose (6 g L^?1) of controlled‐release nitrogen fertilizer (CRF_N) was placed at 0 cm (top layer), 15 cm (middle layer), or 30 cm (bottom layer) depth in the containers in a greenhouse, in addition to an unfertilized treatment (control). After 6 months, seedlings were transplanted to the field and subjected to weekly watering regimes (2 L plant^?1 and unwatered). Morphological and ecophysiological parameters were periodically measured on seedlings, as well as soil electrical conductivity (EC). After 1 year, the shoot : root ratio of unwatered seedlings decreased as a function of CRF_N placement depth, which was attributed to lower shoot growth and not to greater root growth. The root morphology of the bottom layer treatment was negatively affected by high EC in unwatered seedlings. Greater total root length and root volume of the middle layer treatment was found only when well‐watered; however, this did not contribute to improve physiological responses against water stress. The lowest EC and the highest photochemical efficiency, net photosynthesis, and stomatal conductance were shown by unfertilized seedlings, independent of water availability. Our findings suggest that varying depth of CRF_N placement does not contribute significantly to improve root growth under water restriction. Water supplements, independently of the CRF_N location in the substrate, contribute to decrease root zone salinity, and consequently, improve root volume growth.     

Nitrogen forms affect root growth,photosynthesis, and yield of tomato under alternate partial root‐zone irrigation

To increase efficiency of water and nitrogen (N) fertilizer use, this study was conducted with a split‐root pot experiment to investigate the effects of different forms of N fertilizer on root growth, photosynthesis, instantaneous water use efficiency (IWUE), and yield of tomato (Lycopersicon esculentum L.) under alternate partial root‐zone irrigation (APRI). Three irrigation modes comprised conventional irrigation (CI) and two kinds of APRI, i.e., APRI with water content in the drying soil compartment controlled at ≥ 60% or 40% of the water‐holding capacity (APRI‐60, APRI‐40). Two N forms included ammonium‐N and nitrate‐N supplied as calcium nitrate or ammonium sulfate, respectively. The results show that APRI‐60 enhanced root growth and increased leaf IWUE with a slight yield reduction compared with CI regardless of the N form supplied. In contrast, APRI‐40 significantly decreased root growth and inhibited photosynthesis, thereby resulting in a significant yield loss. In addition, at the flowering stage tomato plants grew better with ammonium‐N than nitrate‐N supply; however, at the fruit expansion stage and maturity stage, the tomato plants had a higher biomass accumulation and yield with nitrate‐N than ammonium‐N supply. Therefore, the application of APRI should consider the soil water condition coupled with an appropriate N form. In the present study, APRI controlled at ≥ 60% of the water‐holding capacity (WHC) for the drying soil side with nitrate‐N supply was the best water‐fertilizer supply for tomato cultivation.     

Responses of photosynthesis,chlorophyll fluorescence,and grain yield of maize to controlled‐release urea and irrigation after anthesis

Controlled‐release urea (CRU) is a new type of urea, which may increase crop nitrogen (N)‐use efficiency compared with conventional urea (CU), but the conditions where it outperforms urea are not well defined. A field experiment assessing responses of plant growth and grain yield of maize to CRU and irrigation was conducted on a typical agricultural farm in Shandong, China. Five treatments of the two types of urea (75, 150 kg N ha^–1, 0 kg N ha^–1) were applied as basal fertilizer when sowing maize, and two water treatments (W₀ and W₁) were used 23 d after anthesis. Net photosynthetic rate (P_N) and chlorophyll concentration as well as leaf‐area index (LAI) increased significantly by both CRU and CU application, with the increases being larger in CRU‐treated plants than in CU‐treated plants at grain filling and maturing stages. CRU significantly enhanced the maximum photochemical efficiency (F_v / F_m), PSII coefficient of photochemical fluorescence quenching (q_P), and actual quantum yield of PSII electron transformation (Φ_PSII) but decreased the nonphotochemical quenching (NPQ). Cob‐leaf N concentration of CRU‐treated plants was significantly higher than that of CU‐treated plants under no irrigation, but not in the irrigation treatment 30 d after anthesis. Significant positive correlations were found between cob‐leaf N concentration and P_N both with and without irrigation. Grain yield of maize was significantly higher in the CRU treatment than in the CU treatment under both irrigation conditions. In conclusion, CRU as a basal application appeared to increase the N‐use efficiency for maize relative to CU especially by maintaining N supply after anthesis.     

水氮调控对冬小麦根冠比和水分利用效率的影响研究

通过田间和桶栽试验研究了水、氮调控对冬小麦根冠比和水分利用效率的影响。田间试验结果显示,土壤水分条件对冬小麦根冠生长影响显著。当冬小麦生育期60 cm土层土壤水分维持在田间持水量的60%以上时,根冠比维持稳定状态,不随灌溉次数的增加而变化;当冬小T麦生育期60 cm土层土壤水分低于田间持水量的60%时,土壤越干旱,根冠比越大。桶栽试验结果显示,氮素水平对冬小麦根冠比影响显著,而水氮互作效应对根冠比影响不显著。在所有水分处理条件下,随着施氮量增加,冬小麦根量减少。施氮对冬小麦地上部分和地下部分的影响不同。在水分亏缺条件下,随着氮用量增加,冬小麦经济产量呈增加趋势,水分利用效率与施氮量存在明显正相关关系;而在充分灌溉条件下,产量随着施氮量的增加表现出先增加后降低的趋势,存在一个氮肥用量阈值。因此,水氮通过调控地上地下干物质分配而影响作物产量和水分利用效率,在水分供应受限制条件下,增施氮肥会降低根冠比,更利于地上干物质的积累和经济产量形成。田间试验和桶栽试验均表明,冬小麦根冠比与水分利用效率呈负相关,根冠比大不利于地上部分干物质的积累和作物产量的形成,导致水分利用效率降低。     

灌溉量和施氮量对油用亚麻茎秆抗倒性能及产量的影响

为明确灌水和施氮对油用亚麻(Linum usitatissimum L.)抗倒伏能力和产量的影响,以‘陇亚杂1号’为材料,于2012—2013年以灌溉量为主处理(W1:2 700 m3·hm-2;W2:3 300 m3·hm-2),施氮量为副处理[纯氮量分别为N0:0 kg·hm-2(CK);N1:37.5 kg·hm-2(低氮);N2:112.5 kg·hm-2(中氮);N3:225 kg·hm-2(高氮)],研究灌溉量和施氮量对与油用亚麻抗倒性能相关的形态学特性、茎秆强度、抗倒伏指数及茎秆化学组分含量、产量构成因子及产量的影响。结果表明,随灌溉量的增加,茎秆强度和抗倒伏指数下降,株高增加,重心上移,茎粗、茎壁厚度降低,地上部干重增加,根干重减少,根冠比下降,同时茎秆中纤维素、木质素、可溶性糖和淀粉的含量下降;随施氮量的增加,茎秆强度和抗倒伏指数先升高后降低,株高和重心高度增加,茎粗、茎壁厚度、根干重和根冠比先增后减,地上部干重增加,茎秆中各化学组分含量及产量也先增加后降低。进一步分析发现抗倒伏指数与茎秆强度、茎粗、茎壁厚度、根干重、根冠比、纤维素含量、木质素含量、可溶性糖含量及淀粉含量均呈正相关关系,与株高、重心高度、地上部干重呈负相关关系。低灌水处理(W1)的茎秆强度、抗倒伏指数和产量分别比高灌水处理(W2)高30.55%、41.06%和0.53%,过多灌水不利于油用亚麻茎秆抗倒伏性能和产量的提高;中氮处理(N2)的茎秆强度分别比不施氮(CK)和高氮(N3)处理高36.8%和3.95%,产量分别高15.9%和0.8%,可见油用亚麻的栽培中施氮量不能过高或过低。因此,生产上采用适宜的灌溉量和施氮量是防止油用亚麻倒伏、获得高产、提高生产效益的重要措施。在本试验区,同等肥力土壤条件下,以灌溉量2 700 m3·hm-2和纯施氮量112.5 kg·hm-2为宜。     

Nitrogen Uptake Efficiency and Growth of Bell Pepper in Relation to Time of Exposure to Fertilizer Solution

Irrigation of high‐value vegetable crops on sandy soils with poor water‐retention capacities may result in fertilizer nitrogen (N) displacement below the effective root zone prior to complete crop uptake. As a result, fertilizer N‐uptake efficiency (FUE) of vegetable crops is often relatively low, thereby increasing the potential risk of groundwater contamination. The objective of this study was to determine how time of exposure of the root zone to the N fertilizer (which is referred to as “fertilizer residence time” or t _R), as related to irrigation management, affects N uptake, FUE, growth, and yield of bell pepper (Capsicum annuum L.). Plants were grown in PVC columns with 45 kg of soil equipped with a drainage valve in the bottom of the column. Weekly irrigation with dissolved fertilizers (potassium nitrate; KNO₃) was applied 1, 3, or 7 d before weekly removal of residual soil N by leaching. Weekly N uptake rates were calculated by comparing total N recovery between unplanted (reference) and planted columns. At 77 d after planting, increasing the t _R from 1 to 3 or 7 d increased the weekly N uptake from 1.4 to 10.8 and/or 13.3 kg N ha^?1, respectively. Total calculated plant N accumulations were 19, 72, and 106 kg N ha^?1 for the 1‐, 3‐, and 7‐d t _R treatments, with overall FUE values being 8, 31, and 45%, respectively. It is concluded that during initial growth crop, uptake capacity is limiting, and more frequent (daily) fertilizer injection into the irrigation water may be required to enhance FUE. It is proposed also that via sound or innovative irrigation management practices, fertilizer retention in the root zone can be enhanced, thereby improving crop growth, yield, and FUE while reducing production cost and potential environmental impacts.     

Nitrogen,Phosphorus and Potassium Interactions in Upland Rice

Upland rice is an important crop in South America, including Brazil. Nutrient interactions are important in determining crop yields. A greenhouse experiment was conducted to evaluate interaction among nitrogen (N), phosphorus (P), and potassium (K) in upland rice production. The treatments applied to upland rice grown on an Oxisol were three levels of N (N₀, N₁₅₀ and N₃₀₀ mg kg^?1), three levels of P (P₀, P₁₀₀ and P₂₀₀ mg kg^?1) and three levels of K (K₀, K₁₀₀ and K₂₀₀ mg kg^?1). These treatments were tested in a 3 × 3 × 3 factorial arrangement. Grain yield, shoot dry weight, plant height, root dry weight, maximum root length, panicle number, 1000-grain weight, and grain harvest index were significantly influenced by N, P, and K treatments. The treatment that did not receive P fertilization did not produce panicle or grain. Hence, P was most yield-limiting nutrient compared to two other nutrients. At the N₀P₀K₀ treatment, rice did not produce grains, indicating severe deficiency of these nutrients in Brazilian Oxisols. Maximum grain yield was obtained with the N₃₀₀P₂₀₀K₂₀₀ treatment. Grain yield had significant positive association with plant height, shoot dry weight, root dry weight, maximum root length, 1000-grain weight, panicle number, and grain harvest index. Among these growth and yield components, shoot dry weight had the highest positive association with grain yield and root length minimum positive association with grain yield. Hence, adopting adequate soil and crop management practices can improve growth and yield components and increase grain yield of upland rice.     

时空亏缺调控灌溉和施氮处理对番茄水氮利用的影响

为探索节水灌溉条件下蔬菜的水肥高效利用模式, 采用番茄盆栽试验, 以常规充分灌水为对照, 研究了时空亏缺调控灌溉和氮肥处理对番茄营养器官干物质累积、灌溉水分利用效率、氮素累积及土壤水氮分布的影响。在交替灌溉条件下, 设置控水时期、灌水水平和施氮水平3因素, 控水时期分别为开花座果期和结果期, 2个灌水水平分别为高水和低水, 3个施氮水平分别为高氮、低氮和无氮, 并以常规灌溉作为对照。结果表明: 与常规充分灌水处理相比, 交替灌溉持续高水处理、交替灌溉开花座果期低水处理、交替灌溉结果期低水处理及交替灌溉持续低水处理分别降低干物质累积总量4.52%、11.93%、17.76%和23.94%, 分别降低氮素累积总量1.74%、12.86%、15.50%和22.47%, 分别降低氮素干物质生产效率2.24%、3.93%、2.55%和0.89%, 而分别增加灌溉水分利用效率12.39%、8.99%、15.02%和12.96%。在交替灌溉条件下, 中氮处理的干物质累积、灌溉水分利用效率和氮素累积总量最大。与低氮处理相比, 中氮和高氮处理的氮素干物质生产效率分别降低6.87%~12.70%和17.81%~24.38%, 土壤硝态氮分别提高31.64%~159.58%和57.37%~297.37%。综合考虑干物质累积、水分利用及氮素累积等因素, 番茄适宜的水氮供给模式为交替灌溉持续高水中氮处理: 灌水定额为80%W₀(W₀为常规充分灌溉的灌水定额, 保持土壤含水量为田间持水量的70%~85%), 施氮量为0.30 g(N)·kg^-1(干土)。     

Growth of Tropical Legume Cover Crops as Influenced by Nitrogen Fertilization and Rhizobia

Tropical legume cover crops are important components in cropping systems because of their role in improving soil quality. Information is limited on the influence of nitrogen (N) fertilization on growth of tropical legume cover crops grown on Oxisols. A greenhouse experiment was conducted to evaluate the influence of N fertilization with or without rhizobial inoculation on growth and shoot efficiency index of 10 important tropical cover crops. Nitrogen treatment were (i) 0 mg N kg^?1 (control or N₀), (ii) 0 mg N kg^?1 + inoculation with Bradyrhizobial strains (N₁), (iii) 100 mg N kg^?1 + inoculation with Bradyrhizobial strains (N₂), and (iv) 200 mg N kg^?1 of soil (N₃). The N?×?cover crops interactions were significant for shoot dry weight, root dry weight, maximal root length, and specific root length, indicating that cover crop performance varied with varying N rates and inoculation treatments. Shoot dry weight is considered an important growth trait in cover crops and, overall, maximal shoot dry weight was produced at 100 mg N kg^?1 + inoculation treatment. Based on shoot dry-weight efficiency index, cover crops were classified as efficient, moderately efficient, and inefficient in N-use efficiency. Overall, the efficient cover crops were lablab, gray velvet bean, jack bean, and black velvet bean and inefficient cover crops were pueraria, calopo, crotalaria, smooth crotalaria, and showy crotalaria. Pigeonpea was classified as moderately efficient in producing shoot dry weight.     

Nitrogen and genotype effects on root growth and root survivorship of spring wheat

The nitrogen (N) fertilization of wheat (Triticum aestivum L.) is important for stable and high grain yield. However, the effect of N on root growth and survivorship is poorly understood. The objectives of this study were (1) to determine the effect of varying N availability on the growth and survivorship of roots and (2) to determine whether genotypic variation in N‐related traits are linked to root growth and survivorship. In a two‐year study, two spring wheat cultivars (Albis and Toronit) and an experimental line (L94491) were grown under low (20 kg N ha^–1) and high N supply (270 kg N ha^–1) in lysimeters equipped with minirhizotrons. The genotypes showed significant differences in N‐related traits: total shoot N content, grain N yield, N harvest index, and rate of decline in flag‐leaf greenness. However, there were relatively weak and inconsistent genotypic effects on the time course of root density, root growth during grain filling, and root survivorship. The level of N supply was the factor that most influenced the establishment, growth, and survivorship of roots; the high N supply, depending on the year and genotype, increased growth and survivorship of roots from 0% to 68% and 24% to 34%, respectively.     

Coffee‐husk biochar application increased AMF root colonization,P accumulation,N2 fixation,and yield of soybean grown in a tropical Nitisol,southwest Ethiopia

Low soil fertility and soil acidity are among the major bottlenecks that limit agricultural productivity in the humid tropics. Soil management systems that enhance soil fertility and biological cycling of nutrients are crucial to sustain soil productivity. This study was, therefore, conducted to determine the effects of coffee‐husk biochar (0, 2.7, 5.4, and 16.2 g biochar kg^?1 soil), rhizobium inoculation (with and without), and P fertilizer application (0 and 9 mg P kg^?1 soil) on arbuscular mycorrhyzal fungi (AMF) root colonization, yield, P accumulation, and N₂ fixation of soybean [Glycine max (L.) Merrill cv. Clark 63‐K] grown in a tropical Nitisol in Ethiopia. ANOVA showed that integrated application of biochar and P fertilizer significantly improved soil chemical properties, P accumulation, and seed yield. Compared to the seed yield of the control (without inoculation, P, and biochar), inoculation, together with 9 and 16.2 g biochar kg^?1 soil gave more than two‐fold increment of seed yield and the highest total P accumulation (4.5 g plant^?1). However, the highest AMF root colonization (80%) was obtained at 16.2 g biochar kg^?1 soil without P and declined with application of 9 mg P kg^?1 soil. The highest total N content (4.2 g plant^?1) and N₂ fixed (4.6 g plant^?1) were obtained with inoculation, 9 mg P kg^?1, and 16.2 g biochar kg^?1 soil. However, the highest %N derived from the atmosphere (%Ndfa) (> 98%) did not significantly change between 5.4 and 16.2 g kg^?1 soil biochar treatments at each level of inoculation and P addition. The improved soil chemical properties, seed yield, P accumulation and N₂ fixation through combined use of biochar and P fertilizer suggest the importance of integrated use of biochar with P fertilizer to ensure that soybean crops are adequately supplied with P for nodulation and N₂‐fixation in tropical acid soils for sustainable soybean production in the long term.     

Effects of different water regimes and nitrogen application strategies on grain filling characteristics and grain yield in hybrid rice

In order to optimize N application and understand how the different combinations of water and N management affect grain filling characteristics and yield, we designed three irrigation regimes (W₁ submerged irrigation, W₂ alternate irrigation, W₃ dry cultivation), and different N application strategies at 180 kg ha^?1 in 2010 and 2011. The relationship between grain filling characteristics and grain yield formation were respectively investigated. The results revealed that there were obvious interacting effects of irrigation regime and N application strategies on grain yield and grain-filling characteristics as well. Compared with W₁ and W₃ treatments, under W₂, the N-fertilizer should account for 30% base, 30% tillering, and 40% panicle fertilizer with the last being applied equally at 4th and 2nd leaves emerged from the top. Correlation analysis revealed that grain filling rate during middle grain-filling stage was the largest and contribute more than 50% to grain-filling. Grain yield was significantly related to grain filling rate (G_max or G_mean), final weight of a kernel (A), and mean grain filling rate (MGR) of the early, mid and late stages during grain filling in inferior spikelets, which is the important reason for water and N coupling effect further to increase yield and fertilizer use efficiency.