Timing and splitting of nitrogen fertilizer supply to increase crop yield and efficiency of nitrogen utilization in a wheat–peanut relay intercropping system in China

Agronomically optimizing the timing and rates of nitrogen(N) fertilizer application can increase crop yield and decrease N loss to the environment. Wheat(Triticum aestivum L.)–peanut(Arachis hypogaea L.) relay intercropping systems are a mainstay of economic and food security in China. We performed a field experiment to investigate the effects of N fertilizer on N recovery efficiency, crop yield, and N loss rate in wheat–peanut relay intercropping systems in the Huang-Huai-Hai Plain, China during 2015–2017. The N was applied on the day before sowing, the jointing stage(G30) or the booting stage(G40) of winter wheat, and the anthesis stage(R1) of peanut in the following percentage splits: 50-50-0-0(N1), 35-35-0-30(N2), and 35-0-35-30(N3), using 300 kg N ha-1, with 0 kg N ha-1(N0) as control. ^(15)N-labeled(20.14 atom %) urea was used to trace the fate of N in microplots. The yields of wheat and peanut increased by 12.4% and 15.4% under the N2 and N3 treatments, relative to those under the N1 treatment. The ^(15)N recovery efficiencies( ^(15)NRE) were 64.9% and 58.1% for treatments N2 and N3, significantly greater than that for the N1 treatment(45.3%). The potential N loss rates for the treatments N2 and N3 were23.7% and 7.0%, significantly lower than that for treatment N1(30.1%). Withholding N supply until the booting stage(N3) did not reduce the wheat grain yield; however, it increased the N content derived from ^(15)N-labeled urea in peanuts, promoted the distribution of ^(15)N to pods, and ultimately increased pod yields in comparison with those obtained by topdressing N at jointing stage(N2). In comparison with N2, the N uptake and N recovery efficiency(NRE) of N3 was increased by 12.0% and 24.1%,respectively, while the apparent N loss decreased by 16.7%. In conclusion, applying N fertilizer with three splits and delaying topdressing fertilization until G40 of winter wheat increased total grain yields and NRE and reduced N loss. This practice could be an environment-friendly N management strategy for wheat–peanut relay intercropping systems in China.

Study of Dynamics of Floodwater Nitrogen and Regulation of Its Runoff Loss in Paddy Field-Based Two-Cropping Rice with Urea and Controlled Release Nitrogen Fertilizer Application

The article deals with the effects of urea and controlled release nitrogen fertilizer （CRNF） on dynamics of pH, electronic conductivity （EC）, total nitrogen （TN）, NH4^＋-N and NO3 -N in floodwater, and the regulation of runoff TN loss from paddy field-based two-cropping rice in Dongting Lake, China, and probes the best fertilization management for controlling N loss. Studies were conducted through modeling alluvial sandy loamy paddy soil （ASP） and purple calcareous clayey paddy soil （PCP） using lysimeter, following the sequence of the soil profiles identified by investigating soil profile. After application of urea in paddy field-based two-cropping rice, TN and NHa＋-N concentrations in floodwater reached peak on the 1st and the 3rd day, respectively, and then decreased rapidly over time; all the floodwater NO3--N concentrations were very low; the pH of floodwater gradually rose in case of early rice within 15 d （late rice within 3 d） after application of urea, and EC remained consistent with the dynamics of NH4^＋-N. The applied CRNF, especially 70% CRNF, led to significantly lower floodwater TN and NH4^＋ concentrations, pH, and EC values compared with urea within 15 d after application. The monitoring result for N loss due to natural rainfall runoff indicated that the amount of TN lost in runoff from paddy field- based two-cropping rice with urea application in Dongting Lake area was 7.47 kg ha^-1, which accounted for 2.49% of urea- N applied, and that with CRNF and 70% CRNF application decreased 24.5 and 27.2% compared with urea application, respectively. The two runoff events, which occurred within 20 d after application, contributed significantly to TN loss from paddy field. TN loss due to the two runoffs in urea, CRNF, and 70% CRNF treatments accounted for 72, 70, and 58% of the total TN loss due to runoff over the whole rice growth season, respectively. And the TN loss in these two CRNF treatments due to the first run-off event at the 10th day after application to early rice decreased 44.9 and 44.2% compared with urea, respectively. In conclusion, the 15-d period after application of urea was the critical time during which N loss occurred due to high floodwater N concentrations. But CRNF decreased N concentrations greatly in floodwater and runoff water during this period. As a result, it obviously reduced TN loss in runoff over the whole rice growth season.

Nitrogen uptake and transfer in broad bean and garlic strip intercropping systems

Utilization and transfer of nitrogen （N）in a strip intercropping system of garlic （Allium safivum L.） and broad bean （Vicia faba L.） have been investigated rarely. The objectives of this study were to quantify N uptake and utilization by intercropped broad bean and garlic and determine the magnitude of N transfer from broad bean to garlic. Field and pot trials were carried out in the Erhai Lake Basin in China using ^15N tracer applied to the soil or injected into broad bean plants. Strip intercropping of garlic and broad bean increased N absorption （47.2%） compared with sole crop broad bean （31.9%） or sole crop garlic （40.7%） and reduced soil residual N. Nearly 15% of 15N injected into petioles of broad bean intercropped with garlic was recovered in garlic at harvest, suggesting that N could be transferred from broad bean to strip intercropped garlic. The findings provide a basis for evaluating legumes＇ role in optimizing N fertilization when intercropped with non-legumes.

An united model and simulation of nitrogen transport, uptake and transformation in soil-crop system

Based on the simulation experiments of water and nitrogen transport, transformation and uptaking, under the condition of different cropping pattern of winter wheat in the greenhouse and the condition of different wastewater irrigation plan. An united computing model of crop growth, distribution of roots, water and nitrogen uptaking by roots and transformation in soil crop system was developed. Growth status of crops, root growth condition and water, nitrogen uptaking pattern by roots under different watering and N pollution conditions were simulated and analyzed due to the development of this mathematical model and the identification of parameters and boundary conditions in the greenhouse, so that it provided a primary computing method for selecting an efficient, productive watering and wastewater irrigating plan.

The effects of different autumn-seeded cover crops on subsequent irrigated corn response to nitrogen fertilizer

A common crop rotation in the west Iran is wheat-fallow-corn. The fallow period after wheat harvest (during fall and winter) can lead to soil erosion, nutrient losses (e.g. nitrate leaching) and offsite movement of pesticides. This period is an ideal time to establish a cover crop. In order to investigate the effects of different autumn-seeded cover crops on subsequent irrigated corn response to nitrogen fertilizer, field studies were carried out during the 2007-2008 growing season at the Agricultural Research Farm, Razi University, Kermanshah, Iran. The experiment was conducted in a split plot arrangement based on a randomized complete block design with three replications. The main plots consisted of four cover crops including alfalfa (Medicago sativa L.), berseem clover (Trifolium alexandrinum L.), common vetch (Vicia sativa L.) and winter rye (Secale cereale L.) and a control (no cover crop). The sub plots consisted of two fertilizer N rates (0 and 250 kg ha-1). Cover crops were grown for nearly 5 months and then were incorporated into the soil as green manures. The results indicated that corn plant traits including seed yield, the number of seeds per ear and leaf chlorophyll content were significantly influenced by cover crops. Whereas, the cover crops had no signif-icant effects on the number of ears per plant, 100-seed weight and harvest index of corn. Among the cover crop species, common vetch produced higher dry weight and showed the highest positive effects on the corn plant traits. Dry weight produced by this cover crop was 56.41, 120.16 and 124.19% higher than those of winter rye, berseem clover and alfalfa, respectively. Common vetch enhanced seed yield, the number of seeds per ear and leaf chlorophyll content of corn by 46.30, 21.95 and 8.52%, respectively, compared to control. All of the corn traits under study, except the number of ears per plant and harvest index were significantly improved by nitrogen fertilizer. In general, this study revealed that the autumn-seeded cover crops, especially common vetch can be used to improve corn yield. However, the cover crops should be supplemented with nitrogen fertilizer to obtain optimal results.

Grain Yield and Nitrogen Use Efficiency Vary with Cereal Crop Type and Nitrogen Fertilizer Rate in Ethiopia: A Meta-Analysis

The crop production in Ethiopia is markedly constrained by soil nutrient depletion and limited fertilizer input. Nitrogen is among the most yield-limiting factors of cereal crops, especially in sub-Saharan Africa (SSA). A meta-analysis of 82 studies was carried out to evaluate the response of major cereal crops, viz. wheat, maize, barley, teff, and sorghum, to nitrogen fertilization in Ethiopia. The results showed that N-application significantly increased yields of all the five crops examined herein. The average yields of the treatment effects over controls for the five crops were 3775.8 kg∙ha−1 and 2593.3 kg∙ha−1, respectively. The overall yield response to nitrogen treatments for all the crops was 64.8% (wheat, 96.5%;maize, 40.65%;barley 84.36%;teff, 50.48%;and sorghum;23%). Overall, nitrogen agronomic efficiency (AEN) and partial factor productivity (PFPN) were 18.2 and 71.81 kg∙kg−1, respectively. A downtrend of nitrogen use efficiency with an increase in N rate was realized. The yield response was higher for the nitrogen treatment effects of >100 kg∙N∙ha−1 (123.9%), clay soils (75.46%), low initial soil organic carbon (SOC) and available phosphorous (AP) (92.4% and 101.6%), respectively, Therefore, we recommend the application of nitrogen fertilizer (>100 kg∙N∙ha−1), especially on infertile soils for improved grain yield and NUE in aforementioned cereal crops in Ethiopia and similar regions in sub-Saharan Africa (SSA).

Residue Placement and Rate, Crop Species, and Nitrogen Fertilization Effects on Soil Greenhouse Gas Emissions

High variability due to soil heterogeneity and climatic conditions challenge measurement of greenhouse gas (GHG) emissions as influenced by management practices in the field. To reduce this variability, we examined the effect of management practices on CO2, N2O, and CH4 fluxes and soil temperature and water content from July to November, 2011 in a greenhouse. Treatments were incomplete combinations of residue placements (no residue, surface placement, and incorporation into the soil) and rates (0%, 0.25%, and 0.50%), crop species (spring wheat [Triticum aestivum L.], pea [Pisum sativum L.], and fallow), and N fertilization rates (0.11 and 0.96 g.N.pot-1). Soil temperature was not influenced by treatments but water content was greater under fallow with surface residue than in other treatments. The GHG fluxes peaked immediately following water application and/or N fertilization, with coefficient of variation (CV) ranging from 21% to 46%, 2 and N2O fluxes across measurement dates were greater under wheat or fallow with surface residue and 0.96 g.N.pot-1 than in other treatments. Average CH4 uptake was greater under fallow with surface or incorporated residue and 0.11 g.N.pot-1 than in other treatments. Doubling the residue rate increased CO2 flux by 9%. Greater root respiration, N substrate availability, and soil water content increased CO2 and N2O emissions under wheat or fallow with surface residue and high N rate but fallow with low N rate increased CH4 uptake. Controlled soil and environmental conditions substantially reduced variations in GHG fluxes.

Transgenic approaches for improving use efficiency of nitrogen, phosphorus and potassium in crops

The success of the Green Revolution largely relies on fertilizers, and a new Green Revolution is very much needed to use fertilizers more economically and efficiently, as well as with more environmental responsibility. The use efficiency of nitrogen, phosphorus, and potassium is controlled by complex gene networks that co-ordinate uptake, re-distribution, assimilation, and storage of these nutrients. Great progress has been made in breeding nutrient-efficient crops by molecularly engineering root traits desirable for efficient acquisition of nutrients from soil, transporters for uptake, redistribution and homeostasis of nutrients, and enzymes for efficient assimilation. Regulatory and transcription factors modulating these processes are also valuable in breeding crops with improved nutrient use efficiency and yield performance.

Effect of various crop rotations on rice yield and nitrogen use efficiency in paddy–upland systems in southeastern China

To evaluate the effects of various rotation systems on rice grain yield and N use efficiency, a paddy–upland cropping experiment(2013–2016) was conducted in southeastern China. The experiment was designed using six different rice––winter crop rotations: rice–fallow(RF),rice–wheat(RW), rice–potato with rice straw mulch(RP), rice–green manure(Chinese milk vetch; RC–G), rice–oilseed rape(RO), and rice–green manure crop(oilseed rape with fresh straw incorporated into soil at flowering; RO–G) and three N rates, N0(0 kg N ha-1), N1(142.5 kg N ha-1), and N2(202.5 kg N ha-1). Average rice yields in the RF(5.93 t ha-1) rotation were significantly lower than those in the rotations with winter crops(7.20–7.48 t ha-1)under the N0 treatment, suggesting that incorporation of straw might be more effective for increasing soil N than winter fallow. The rice yield differences among the rotations varied by year with the N input. In general, the grain yields in the RP and RO–G rotations –were respectively 11.6–28.5% and 14.80–37.19% higher than those in the RF in plots with N applied. Increasing the N rate may have tended to minimize the average yield gap between the RF and the other rotations; the yield gaps were 18.55%, 4.14%, and 0.23% in N0, N1, and N2, respectively. However, the N recovery efficiency in the RF was significantly lower than that in other rotations, except for 2015 under both N1 and N2 rates, a finding that implies a large amount of chemical N loss. No significant differences in nitrogen agronomic efficiency(NAE) and physiological efficiency(NPE) were found between the rotations with legume(RC–G) and non–legume(RO and RW) winter crops, a result that may be due partly to straw incorporation. For this reason, we concluded that the return of straw could reduce differences in N use efficiency between rotations with and without legume crops. The degree of synchrony between the crop N demand and the N supply was evaluated by comparison of nitrogen balance degree(NBD) values. The NBD values in the RP and RW were significantly lower than those in the other rotations under both N1 and N2 rates. Thus,in view of the higher grain yield in the RP compared to the RW under the N1 rate, the RP rotation might be a promising practice with comparable grain yield and greater N use efficiency under reduced N input relative to the other rotations. The primary yield components of the RF and RP were identified as number of panicles m-2 and numbers of kernels panicle-1, respectively. The NAE and NPE were positively correlated with harvest index, possibly providing a useful indicator for evaluating N use efficiency.

Fate of Nitrogen from Organic and Inorganic Sources in Rice-Wheat Rotation Cropping System

The lower availability of N is one of the most important limiting factors impeding crop yield enhancement among the various factors that affect crop yield under the multiple-cropping agroecosystem in China.In this study,the recovery of a single application of 15N-labeled fertilizer or residues in rice-wheat cropping system was determined,in order to provide theoretical foundation for the nitrogen management in sustainable agricultural production.A continuous trace experiment was conducted for 15N microplots by using randomized block design with four treatments and four replications（T1 = 15N-labeled fertilizer with crop residue incorporation,T2 = 15N-labeled residues,T3 = 14N fertilizer to generate unlabeled crop residue,and T4 = 15Nlabeled fertilizer without crop residue incorporation）.Our results showed that,on average,17.17 and 12.01% of crop N was derived from N fertilizer and 15N-labeled residues,respectively during the first growing season,suggesting that approximately 82.83 or 87.99% of crop N was derived directly from soil N pool.There was a larger difference in the 15N recovery pattern in crop when N was applied as fertilizer or residues,i.e.,most of crop N derived from N fertilizer was absorbed in the first growing season（92.04%）,and the relevant value was 38.03% when 15N-labeled residues were applied.This implied that most of N fertilizer was recovered in the present cropping season,while a longer residue effect will be found for 15N-labeled residues.Thus,the average recovery of N fertilizer and N residue in the soil after the first growing season was 33.46 and 85.64%,respectively.The recovery of applied N in soil when N was applied as residues was significantly higher than that when N was applied as fertilizer.There was a larger difference in the total 15N recovery in plant and soil when N was applied as fertilizer or residues.By the end of the fifth or sixth cropping season,the total 15N recovery in plant and soil when N was applied as fertilizer or residues were estimated at 64.38 and 79.11%,respectively.On the contrary,there was little difference between the practices of residue incorporation and residue removal following the N fertilizer application.N fertilizer appeared to be more readily available to crops than residue-N,and residue-N replenished soil N pool,especially N in soil organic matter,much more than N fertilizer after six growing seasons.Therefore,residue-N is a better source for sustaining N content of soil organic matter.Thus,one possible management practice is to use both organic and inorganic N sources simultaneously to improve the use efficiency of N while protecting the sustainability of soil.

Integration of Growing Milk Vetch in Winter and Reducing Nitrogen Fertilizer Application Can Improve Rice Yield in Double-Rice Cropping System

To study whether integrative fertilization [growing milk vetch in winter and reducing the dose of chemical nitrogen(N) fertilizer] can improve rice yield, and to reveal the underlying regulatory mechanisms for integrative fertilization, a three-year field trial including two treatments, milk vetch-rice-rice(MRR) and winter fallow-rice-rice(FRR), was conducted in 2010, 2011 and 2012.Our results demonstrated that the MRR treatment could significantly improve rice yield compared with the FRR treatment, especially when the application ratio of milk vetch and chemical fertilizer was 1:2.MRR treatment increased the effective panicle number and the spikelet number per panicle.In addition, a higher tillering number, leaf area index, photosynthetic-potential and photosynthetic-potential to grain ratio were observed in MRR treatment, which could provide enough dry matter for yield formation.Moreover, in MRR treatment, we discovered a higher transportation ratio and transformation ratio of dry matter in culm and leaves, and a stronger total sink capacity and spikelet-root bleeding intensity at the heading stage and 15 d after heading.Furthermore, the MRR treatment showed higher total N, phosphorus and potassium uptakes than FRR treatment, which was associated with the higher root dry weight in each soil layers.These results suggest that growing milk vetch in winter can improve rice yield under less chemical N fertilizer application, which is due to the improvement of soil nutrient status and the increased of rice root growth and development.

OILCROP-SUN Model Relevance for Evaluation of Nitrogen Management of Sunflower Hybrids in Sargodha, Punjab

The experiments were conducted to evaluate the performance of crop system (DSSAT) OILCROP-SUN model simulating growth & development and achene yield of sunflower hybrids in response to nitrogen under irrigated conditions in semi arid environment, Sargodha, Punjab. The model was evaluated with observed data collected in trials which were conducted during spring season in 2010 and 2011 in Sargodha, Punjab, Pakistan. Split plot design was used in layout of experiment with three replications. The hybrids (Hysun-33 & S-278) and N levels (0, 75, 150 and 225 kg.ha-1) were allotted in main and sub plots, respectively. The OILCROP-SUN model showed that the model was able to simulate growth and yield of sunflower with an average of 10.44 error% between observed and simulated achene yield (AY). The results of simulation analysis indicated that nitrogen rate of 150 kg.N.ha-1 (N3) produced the highest yield as compared to other treatments. Furthermore, the economic analysis through mean Gini Dominance also showed the dominance of this treatment compared to other treatment combinations. Thus management strategy consisting?of treatment 150 kg.N.ha-1 was the best for high yield of sunflower hybrids.

OILCROP-SUN Model for Nitrogen Management of Diverse Sunflower (<i>Helianthus annus</i>L.) Hybrids Production under Agro-Climatic Conditions of Sargodha, Pakistan

Decision support system for agro-technology transfer (DSSAT), OIL CROP-SUN Model was used to stimulate the phenology, growth, yield of different two sunflower hybrids. i.e. Hysun-33 and S-78 by applying different nitrogen levels. The effect of nitrogen (N) on growth and yield components of different sunflower (Helianthus annuus L.) hybrids were evaluated under agro-climatic conditions of Sargodha, Pakistan during spring 2013. The experiment was laid out in a randomized complete block design with split plot arrangement having three replications, keeping cultivars in the main plots and nitrogen levels (0, 45, 90,135 and 180 kg/ha) in sub plots. OIL CROP-SUN Model showed that the model was able to simulate the growth and yield of sunflower with an average of 10.44 error% between observed and simulate achene yield (AY). The result of simulation indicates that nitrogen rate of 180 kg/ha produced highest achene yield in S-78 hybrid as compared to other treatments and Hysun-33 cultivar.

Integrated numerical model of nitrogen transportation,absorption and transformation by two-dimension in soil-crop system

A series of simulation experiments of nitrogen transportation, absorption and transformation were conducted, and the different cropping patterns of winter wheat and wastewater irrigation plans were taken into consideration. Based on the experiments, an integrated model of crop growth, roots distribution, water and nitrogen absorption by roots, water and nitrogen movement and transformation in soil-crop system by two-dimension was developed. Parameters and boundary conditions were identified and an effective computing method for optimizing watering and wastewater irrigating plans was provided.

禾本科作物联合固氮研究进展

生物固氮是唯一能将空气中“免费”的氮气转化为化合态氮的生物学过程。一般认为豆科作物具有共生固氮能力,间套种豆科作物已成为补充农田氮素的重要方式。越来越多的证据证明禾本科作物也具有较高的联合固氮潜力,大量联合固氮菌不仅定殖在根际、根内,还可以定殖在植株地上部如茎维管束、叶际中,表明禾本科作物固氮微生物可能为避免复杂的土壤环境,开辟了一条“体内高效固氮”的新途径。本文回顾了近年来玉米、小麦、水稻、甘蔗等禾本科作物在联合固氮部位、调控途径、菌群构建等方向取得的创新进展,重点介绍了固氮菌除了与宿主植物存在互作关系外,还与其他功能细菌、真菌和病毒之间存在潜在的相互作用。基于生物固氮多功能合成菌群在植物营养和促生等领域表现出的巨大应用前景和潜力,提出了当前禾本科作物联合固氮研究的前沿热点和难点,即如何综合利用“自上而下”和“自下而上”策略,筛选关键功能类群并结合基因组尺度代谢模型,构建群落稳定、功能多样、效果显著的合成菌剂,为生物固氮在农业生产中广泛应用提供强有力的技术支撑。

“油-稻-稻”三熟制早熟冬油菜氮高效基因型及鉴定指标筛选

【目的】旨在筛选适宜“油-稻-稻”三熟制的氮高效早熟冬油菜基因型及其简易筛选指标。【方法】利用田间小区试验,选用了生育期185 d以下的的适宜“油-稻-稻”三熟制种植的14种早熟冬油菜基因型,进行正常施氮(N_(1))和不施氮(N_(0))处理。根据不同冬油菜基因型氮肥利用率(NUE)的差异,利用树状聚类分析进行分类,形成高、中、低3种氮效率基因型。同时通过逆向溯源的方法,观察分析3种氮效率基因型在不同氮水平条件下的产量构成、主要农艺性状、干物质积累及氮素吸收等方面的表现特征。总结分析出氮高效冬油菜基因型的一些简易判断的指标。【结果】不同氮效率基因型冬油菜在产量形成、主要农艺性状等方面存在显著差异。N1处理下成熟期早熟冬油菜的主要农艺性状的表型值和变异系数基本表现大于N0处理。因此,以N1处理下不同基因型的农艺性状表现作为不同氮效率基因型的鉴别标准。N1处理下,氮高效基因型比氮中效和氮低效基因型产量高、单株角果数多、每角粒数多、株高高、主花序长、一级分枝数多、角果密度高、各部位干物质积累量高、籽粒中氮含量高、氮肥偏生产力、氮肥农学效率、氮肥生理利用率和氮收获指数均较高。【结论】沣油737是适合南方“油-稻-稻”三熟制的氮高效早熟冬油菜;正常施氮条件下,成熟期较多的单株角果数与每角粒数,以及较高株高是判断早熟冬油菜氮高效基因型的简易指标。

河西灌区减氮条件下小麦复种绿肥的水分利用及经济效益

【目的】针对河西绿洲灌区作物生产中氮肥施用过量、水资源利用效率与经济效益较低等问题,探讨麦后复种绿肥及适量减施化学氮肥对小麦农田耗水特性及经济效益的影响。【方法】2019—2020年在甘肃省河西绿洲灌区进行裂区试验,主区设置麦后复种绿肥(W-G)和单作小麦(W)两种种植模式;副区为5个施氮水平,分别为不施氮肥(N_(0))、常规施氮(180 kg·hm^(-2),N_(4))、减施45%氮肥(N_(1))、减施30%氮肥(N_(2))和减施15%氮肥(N_(3))。测定不同处理下小麦绿肥体系产量、水资源利用效率及经济效益。【结果】麦后复种绿肥以及适量减施化学氮肥显著提高小麦籽粒产量和系统生物热能产,2019和2020年,W-G较W处理籽粒产量分别提高10.8%和12.4%,系统生物热能产分别提高37.8%和40.3%;麦后复种绿肥结合减氮15%(W-G-N_(3))较单作小麦结合减氮15%(W-N_(3))和单作小麦传统施氮(W-N_(4))处理小麦分别增产6.9%—16.7%和7.9%—13.6%,生物热能产提高52.0%—62.2%和27.1%—58.9%。W-G较W小麦生育阶段耗水量降低6.3%—16.0%,W-G-N_(3)较W-N_(3)和W-N_(4)小麦季耗水量分别降低13.4%—20.5%和20.8%—29.0%,W-G由于绿肥生长季消耗水分,总耗水量显著高于W。W-G较W小麦水分利用效率分别提高7.9%和19.2%;2019年度W-G-N_(3)较W-N_(3)和W-N_(4)小麦水分利用效率分别提高23.5%和5.1%,差异显著。W-G-N_(3)可有效提高系统单位耗水生物热能产,较W-N_(3)和W-N_(4)分别提高2.7%—14.5%和9.3%—17.5%。W-G较W增加了成本投入,总产值也随之提高;2019年度W-G-N_(3)较W-N_(3)和W-N_(4)纯收益分别提高9.8%和9.5%,2020年度W-G-N_(3)较W-N_(3)和W-N_(4)纯收益则分别降低了15.6%和15.7%;2019和2020年W-G较W产投比分别降低20.7%和23.1%,W-G-N_(3)较W-N_(3)和W-N_(4)产投比降低比例均为14.8%—23.1%,W-G因较多的资源投入降低了系统单方水效益。【结论】在河西绿洲灌区,麦后复种绿肥结合适量减施化学氮肥能够提高作物产量和经济效益,水资源利用效率也随之提高,其中麦后复种绿肥结合减量15%施氮处理的综合效果最好,可作为提高水资源利用及农民收益的理想种植模式及施氮水平。

氮肥运筹与化学调控对双季稻产量及其抗倒伏特性的影响

以早稻品种陆两优996、株两优819及晚稻品种H优518、盛泰优018为材料,于2020年开展大田试验,设计3种氮肥运筹方式N1、N2、N3(分蘖肥、穗肥、粒肥用量比分别为7∶2∶1、6∶3∶1、5∶4∶1)与2种化学调控剂多效唑(C1)、壳寡糖(C2)双因素试验,研究氮肥运筹方式和化学调控对水稻产量及抗倒伏能力的影响。结果表明:氮肥运筹和化学调控对水稻产量影响显著,早、晚稻各品种产量均以N2C2处理的最高,主要通过提高植株有效穗数而增产;与N1相比,N2和N3降低了茎秆高度、节间长度和重心高度,增加了茎粗、茎壁厚度和节间充实度,茎秆抗倒伏能力增强,且N2优于N3处理;与对照处理(C3,喷施清水)相比,C1和C2均降低了水稻茎秆高度、重心高度和节间长度,增加了茎粗、茎壁厚度和节间充实度,从而提高了水稻抗倒伏能力;从互作效应来看,N2C1、N2C2和N3C1处理的茎粗和茎壁厚度较大,倒3与倒4节节间长度较短,节间充实度和抗折力较高,倒伏指数较低。综合考虑各品种倒伏指数和产量性状,N2C2处理,即分蘖肥、穗肥、粒肥施用比例为6∶3∶1条件下,于拔节初期喷施壳寡糖,可在提高双季稻抗倒伏能力的同时获得最高产量。

长期施用控释氮肥对潮土区麦-玉轮作作物产量的影响及土壤氮素供应特征研究

本研究以位于山东德州的连续10年控释氮肥长期定位试验为平台,在小麦—玉米轮作体系下,试验设置不施氮肥(PK)、农民习惯施肥(FP)、优化施肥(OPT)、控释氮肥(CRF1)和控释氮肥减量20%(CRF2)5个处理,分别在玉米抽雄期、灌浆期和小麦拔节期、孕穗期、灌浆期、成熟期采集土壤样品,测定土壤pH值、氮磷钾全量养分、铵态氮、硝态氮、碱解氮含量,测定不同处理玉米、小麦及作物周年产量,以探究长期施用控释氮肥对潮土区麦-玉轮作作物产量的影响及土壤氮素供应特征。结果表明,长期施用控释氮肥可显著提升土壤氮素供应能力,CRF1处理与OPT处理相比,玉米抽雄期和灌浆期土壤碱解氮含量分别提升14.10%和9.45%,铵态氮在抽雄期提升125.53%,小麦拔节期铵态氮和硝态氮分别提升63.73%和200.35%。与FP处理相比,CRF1处理玉米、小麦和周年产量分别显著提高13.13%、16.73%和14.89%,而CRF2处理的产量无显著变化。随机森林模型分析发现,不同施肥模式下玉米产量与灌浆期土壤碱解氮和成熟期土壤全氮含量密切相关,小麦产量则受拔节期土壤硝态氮、孕穗期碱解氮和铵态氮、灌浆期碱解氮以及成熟期土壤全氮、碱解氮含量的综合调控。综上所述,控释氮肥可通过调控氮素释放提高玉米和小麦关键生育期的土壤全氮、碱解氮、硝态氮和铵态氮含量,进而显著提高作物产量,且在减量20%控释氮肥下仍可保证作物不减产。

长期不同施肥模式对大麦–双季稻田根际土壤有机氮组分的影响

根际土壤有机氮组分在土壤养分和作物氮素营养中具有重要作用。本研究依托长期(37年)定位施肥试验田,设置4个施肥处理:不施肥对照(CK)、单独施用化肥(CF)、秸秆还田+化肥(RF)和30%有机肥+70%化肥(OM),于晚稻成熟期测定大麦–双季稻田根际土壤基础理化性质、微生物生物量氮和有机氮组分(氨基酸态氮、氨基糖态氮、酸解氨态氮、酸解未知态氮、非酸解性氮)含量。研究表明:相对CK处理,RF和OM处理显著增加了稻田根际土壤有机碳、全氮、铵态氮和硝态氮的含量。RF和OM处理土壤微生物生物量氮含量分别比CK处理增加了19.8%和30.7%。酸解性氮作为根际土壤全氮的主体部分,占全氮的59.61%~72.06%;各处理根际土壤酸解性氮含量大小顺序表现为OM>RF>CF>CK。各施肥处理中,酸解有机氮中的氨基糖态氮、氨基酸态氮和酸解未知态氮含量均以OM处理最大,分别比CK处理增加139.3%、47.9%和110.0%;酸解氨态氮以RF处理最大,比CK处理增加69.9%。土壤有机碳、全氮、铵态氮、硝态氮与土壤氨基酸态氮、氨基糖态氮、酸解未知态氮以及微生物生物量氮均呈极显著(P<0.01)正相关。因此,秸秆、有机肥配施化肥均能有效提高大麦–双季稻田根际土壤的供氮能力,是改善稻田土壤肥力的有效手段。