Soil C and N dynamics and maize (Zea may L.) yield as affected by cropping systems and residue management in North-western Pakistan

This paper presents the results of irrigated rotation experiment, conducted in the North West Frontier Province (NWFP), Pakistan, during 1999–2002 to evaluate effects of residues retention, fertilizer N and legumes in crop rotation on yield of maize (Zea mays L.) and soil organic fertility. Chickpea (Cicer arietinum L) and wheat (Triticum aestivum L) were grown in the winters and mungbean (Vigna radiata) and maize in the summers. Immediately after grain harvest, above-ground residues of all crops were either completely removed (−residue), or spread across the plots and incorporated by chisel plough by disc harrow and rotavator (+residue). Fertlizer N rates were nil or 120 kg ha⁻¹ for wheat and nil or 160 kg ha⁻¹ for maize. Our results indicated that post-harvest incorporation of crop residues significantly (p < 0.05) increased the grain and stover yields of maize during both 2000 and 2001. On average, grain yield was increased by 23.7% and stover yield by 26.7% due to residue incorporation. Residue retention also enhanced N uptake by 28.3% in grain and 45.1% in stover of maize. The soil N fertility was improved by 29.2% due to residue retention. The maize grain and stover yields also responded significantly to the previous legume (chickpea) compared with the previous cereal (wheat) treatment. The legume treatment boosted grain yield of maize by 112% and stover yield by 133% with 64.4% increase in soil N fertility. Similarly, fertilizer N applied to previous wheat showed considerable carry over effect on grain (8.9%) and stover (40.7%) yields of the following maize. Application of fertilizer N to current maize substantially increased grain yield of maize by 110%, stover yield by 167% and soil N fertility by 9.8% over the nil N fertilizer treatment. We concluded from these experiments that returning of crop residues, application of fertilizer N and involvement of legumes in crop rotation greatly improves the N economy of the cropping systems and enhances crop productivity through additional N and other benefits in low N soils. The farmers who traditionally remove residues for fodder and fuel will require demonstration of the relative benefits of residues return to soil for sustainable crop productivity.     

Nitrogen acquisition by pea and barley and the effect of their crop residues on available nitrogen for subsequent crops

Nitrogen acquisition by field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) grown on a sandy loam soil and availability of N in three subsequent sequences of a cropping system were studied in an outdoor pot experiment. The effect of crop residues on the N availability was evaluated using ¹⁵N-labelled residues. Field pea fixed 75% of its N requirement and the N₂ fixation almost balanced the N removed with the seeds. The barley crop recovered 80% of the ¹⁵N-labelled fertilizer N supplied and the N in the barley grain corresponded to 80% of the fertilizer N taken up by the crop. The uptake of soil-derived N by a test crop (N catch crop) of white mustard (Sinapis alba L.) grown in the autumn was higher after pea than after barley. The N uptake in the test crop was reduced by 27% and 34% after pea and barley residue incorporation, respectively, probably due to N immobilization. The dry matter production and total N uptake of a spring barley crop following pea or barley, with a period of unplanted soil in the autumn/winter, were significantly higher after pea than after barley. The barley crop following pea and barley recovered 11% of the pea and 8% of the barley residue N. The pea and barley residue N recovered constituted only 2.5% and <1%, respectively, of total N in the N-fertilized barley. The total N uptake in a test crop of mustard grown in the second autumn following pea and barley cultivation was not significantly influenced by pre-precrop and residue treatment. In the short term, the incorporation of crop residues was not important in terms of contributing N to the subsequent crop compared to soil and fertilizer N sources, but residues improved the conservation of soil N in the autumn. In the long-term, crop residues are an important factor in maintaining soil fertility and supplying plant-available N via mineralization.     

Influence of crop residue management, cropping system and N fertilizer on soil N and C dynamics and sustainable wheat (Triticum aestivum L.) production

Management of N is the key for sustainable and profitable wheat production in a low N soil. We report results of irrigated crop rotation experiment, conducted in the North West Frontier Province (NWFP), Pakistan, during 1999–2002 to evaluate effects of residue retention, fertilizer N application and mung bean (Vigna radiata) on crop and N yields of wheat and soil organic fertility in a mung bean–wheat sequence. Treatments were (a) crop residue retained (+residue) or (b) removed (−residue), (c) 120 kg N ha⁻¹ applied to wheat, (d) 160 kg N ha⁻¹ to maize or (e) no nitrogen applied. The cropping system was rotation of wheat with maize or wheat with mung bean. The experiment was laid out in a spit plot design. Postharvest incorporation of crop residues significantly (p < 0.05) increased the grain and straw yields of wheat during both years. On average, crop residues incorporation increased the wheat grain yield by 1.31 times and straw yield by 1.39 times. The wheat crop also responded strongly to the previous legume (mung bean) in terms of enhanced grain yield by 2.09 times and straw yield by 2.16 times over the previous cereal (maize) treatment. Application of fertilizer N to previous maize exerted strong carry over effect on grain (1.32 times) and straw yield (1.38 times) of the following wheat. Application of N fertilizer to current wheat produced on average 1.59 times more grain and 1.77 times more straw yield over the 0 N kg ha⁻¹ treatment. The N uptake in wheat grain and straw was increased 1.31 and 1.64 times by residues treatment, 2.08 and 2.49 times by mung bean and 1.71 and 1.86 times by fertilizer N applied to wheat, respectively. The soil mineral N was increased 1.23 times by residues, 1.34 times by mung bean and 2.49 times by the application of fertilizer N to wheat. Similarly, the soil organic C was increased 1.04-fold by residues, 1.08 times by mung bean and 1.00 times by the application of fertilizer N. We concluded that retention of residues, application of fertilizer N and involvement of legumes in crop rotation greatly improves the N economy of the cropping system and enhances crop productivity in low N soils.     

Soil microbial biomass and nitrogen supply in an irrigated lowland rice soil as affected by crop rotation and residue management

 Processes that govern the soil nitrogen (N) supply in irrigated lowland rice systems are poorly understood. The objectives of this paper were to investigate the effects of crop rotation and management on soil N dynamics, microbial biomass C (C_BIO) and microbial biomass N (N_BIO) in relation to rice N uptake and yield. A maize-rice (M-R) rotation was compared with a rice-rice (R-R) double-cropping system over a 2-year period with four cropping seasons. In the M-R system, maize (Zea mays L.) was grown in aerated soil during the dry season (DS) followed by rice (Oryza sativa L.) grown in flooded soil during the wet season (WS). In the R-R system, rice was grown in flooded soil in both the DS and WS. Three fertilizer N rates (0, 50 or 100 kg urea-N ha^–1 in WS) were assigned to subplots within the cropping system main plots. Early versus late crop residue incorporation following DS maize or rice were established as additional treatments in sub-subplots in the second year. In the R-R system, the time of residue incorporation had a large effect on NO₃ ^–-N accumulation during the fallow period and also on extractable NH₄ ⁺-N, rice N uptake and yield in the subsequent cropping period. In contrast, time of residue incorporation had little influence on extractable N in both the fallow and rice-cropping periods of the M-R system, and no detectable effects on rice N uptake or yield. In both cropping systems, C_BIO and N_BIO were not sensitive to residue incorporation despite differences of 2- to 3-fold increase in the amount of incorporated residue C and N, and were relatively insensitive to N fertilizer application. Extractable organic N was consistently greater after mid-tillering in M-R compared to the R-R system across N rate and residue incorporation treatments, and much of this organic N was α-amino N. We conclude that N mineralization-immobilization dynamics in lowland rice systems are sensitive to soil aeration as influenced by residue management in the fallow period and crop rotation, and that these factors have agronomically significant effects on rice N uptake and yield. Microbial biomass measurements, however, were a poor indicator of these dynamics. Received: 31 October 1997     

河西绿洲灌区玉米间作绿肥根茬还田的氮肥减施效应

  【目的】  明确玉米与间作豆科绿肥根茬还田生产方式在河西绿洲灌区的氮肥减施效应。  【方法】  玉米间作豆科绿肥,绿肥(针叶豌豆和毛叶苕子)地上部乂割做饲草根部还田,定位试验位于甘肃河西绿洲,始于2011年,至本试验取样时已进行了10年。试验共设8个处理,包括无绿肥根茬还田条件下后茬玉米不施肥对照,施常规量氮肥(N 375 kg/hm2),只有针叶豌豆、毛叶苕子根部还田,以及根部还田配合常规氮肥量的80%、90%。于2020年玉米收获后测产,并测定了玉米秸秆和籽粒氮、磷、钾养分含量,同时分析了0—20 cm土壤有机质、速效氮磷钾含量及土壤氮库(全氮、有机氮、无机氮、颗粒态有机氮、可溶性有机氮、土壤微生物量氮)。  【结果】  与常规施氮肥相比,根茬单独还田降低了玉米产量;绿肥根茬配施80%、90%常规量氮肥处理之间的玉米籽粒产量没有显著变化,其中针叶豌豆配合80%常规量氮肥还显著增加了玉米产量7.6%;玉米地上部氮磷钾累积量略有增加,而籽粒氮、磷、钾养分累积量分别增加了31.7%～56.4%、37.8%～60.0%、61.7%～96.8%;玉米氮肥农学效率、偏生产力、氮素吸收效率和氮肥表观利用率均显著增加,以针叶豌豆根茬配施80%常规量氮肥处理的增加幅度最高,增加值分别为43.6%、34.5%、107.9%、35.8个百分点 (P<0.05)。采用改进的内梅罗指数法对土壤综合肥力进行评价,以针叶豌豆根茬还田配施80%常规量氮肥处理提升土壤肥力的效果最为显著,土壤综合肥力指数较常规施氮肥处理提升23.0%。偏最小二乘法路径模型和聚合增强树分析表明,施肥处理主要通过调节土壤氮贮量影响玉米产量,土壤全氮、无机氮对产量的贡献率较高,分别为36.5%、26.8%。  【结论】  绿肥根茬连续还田条件下,减少后茬玉米氮肥常规用量的20%可维持甚至提高玉米产量,大幅提升玉米的氮磷钾吸收量和氮肥表观利用率。根茬还田配合适量氮肥可以通过提升土壤氮库贮量提高土壤综合肥力。在河西走廊,玉米产量和环境效益俱佳的栽培管理方式是针叶豌豆根茬还田配合80%的常规氮肥用量,毛叶苕子根茬还田配合80%～90%的常规氮肥用量。     

秸秆还田提高水稻-油菜轮作土壤固氮能力及作物产量

为探讨西南山区水稻-油菜轮作模式下秸秆还田对作物产量和土壤氮素固持能力的影响,于2013-2015年在洱海流域稻油轮作农田中设置空白处理(CK)、单施化肥(CF)、化肥+玉米秸秆(CFMS)以及化肥+蚕豆秸秆(CFBS)4个处理,测定分析了作物产量、土壤微生物量及土壤理化性质等关键指标。结果表明,与CF处理相比,秸秆还田提高水稻、油菜产量及其地上部含氮量,增加氮素有效输出。不同处理土壤微生物量碳、氮质量分数存在差异,其大小顺序为:CFMSCFBSCFCK。与土壤碳氮比相比,土壤微生物熵和微生物量C/N对秸秆还田做出快速响应,秸秆还田提高土壤微生物熵,降低微生物量C/N。此外,秸秆还田显著降低油菜收获后的土壤硝态氮残留(P0.05),与CF相比,玉米秸秆和蚕豆秸秆还田分别使土壤硝态氮残留量减少11.6%~55.0%和13.7%~52.3%。可见,中国西南山区稻油轮作模式下秸秆还田能提高作物产量和含氮量,增强土壤微生物氮素固持能力,有效降低土壤氮素流失风险,且玉米秸秆在增产、固氮方面的作用优于蚕豆秸秆。结果可为提高西南山区水稻、油菜产量,增强土壤氮素固持能力,降低土壤氮素流失风险提供参考。     

旱地土壤中残留肥料氮的动向及作物有效性

氮素是作物生长最重要的必需元素之一。合理施用氮肥能促进作物生长并提高产量,但是,过多施用氮肥则抑制作物生长并导致大量的肥料氮残留在土壤中,这部分氮素不但会引起土壤养分不平衡,而且为生态环境带来潜在威胁,因此,研究残留氮的动向及作物有效性可为合理施用化肥氮、高效利用土壤残留氮素和减少残留氮素的损失提供依据。应用~(15)N示踪技术,通过4年定位试验,研究了黄土高原南部旱地冬小麦/夏玉米轮作过程中土壤残留肥料氮的变化及作物吸收利用。在冬小麦和夏玉米轮作的第一个周期,为了制造高肥料氮残留背景,于冬小麦播种前向微区施入240 kg hm~(-2)的~(15)N标记氮素;在夏玉米拔节期,为了研究氮肥施入对残留肥料氮的影响,设置0和120 kg hm~(-2)两个氮水平,以普通尿素施入微区。在第2至第4个轮作周期内,为了分析残留肥料氮的动向及其对作物的有效性,微区内不施任何肥料。结果发现,冬小麦播种前施用的~(15)N标记氮肥于收获期在0~200 cm土壤剖面中均有残留,但大部分累积在0~40 cm土层中,累积总量达到200.9 kg hm~(-2),占当季施入量的83.7%。在随后的夏玉米生长季残留的肥料氮迅速减少,之后随生长季的后移缓慢减少,然后保持相对稳定。经过4年的冬小麦/夏玉米轮作,0~300 cm土壤剖面仍残留大量的~(15)N肥料,后季不追施氮肥和追施氮肥处理的残留量分别为47.1 kg hm~(-2)和54.0 kg hm~(-2)。可见,有一部分肥料氮被固定在土壤有机质中。作物对残留氮的回收量逐年减少,且因后季追施氮肥与否而异,4年中作物对肥料氮的总利用率不追施氮肥和追施氮肥处理的分别为46.9%和50.4%,其中在第1个轮作周期中,小麦和玉米的总利用率分别41.6%和42.0%,后3年利用率分别仅有5.3%和8.4%;4年中残留~(15)N的损失率分别达38.1%和29.7%,其损失主要发生在第1个轮作周期的夏玉米生长季节。说明,在旱地土壤上,氮肥的残留是不可避免的,残留肥料氮的有效性较低,只有少量被作物逐年吸收,一部分以有机形态残留在土壤剖面中,另一部分发生了无效损失。后季追施氮肥可促进作物对土壤残留肥料氮的吸收且增加肥料氮在土壤中的保留,减少残留肥料氮的无效损失,但是以自身的大量损失为代价的。     

黄土高原旱地冬小麦/夏玉米轮作体系土壤的氮素平衡

在黄土高原南部旱地,通过田间小区试验研究了传统施肥方式下冬小麦/夏玉米轮作体系中土壤的氮素平衡。结果表明:土壤残留矿质态氮(Nmin)对作物产量和施用氮肥效果有重要影响,前季作物残留土壤Nmin可以促进后季作物生长,使氮肥增产效应不明显;冬小麦生长季节施氮240.kg/hm2可以增加产量和作物吸氮量,但其氮肥利用率只有39.7%,大部分以Nmin残留于0200cm土壤中或以其他途径损失;由于冬小麦季节残留肥料氮的后效,使夏玉米生长季节的氮肥利用率很低,施氮120和240.kg/hm2的氮肥利用率分别只有22.4%和3.9%,而在0200cm土层残留率则达到51.1%和87.2%;经过冬小麦、夏玉米一个轮作周期后,施氮量为240、360和480.kg/hm2时作物的氮肥利用率平均为52.2%4、2.2%和28.0%,而相应的土壤残留率平均为12.4%、25.3%和49.8%,表观损失率平均为35.4%、32.5%和22.2%。表明在土壤残留Nmin较高的条件下,夏玉米生长季节施氮量较低时盈余氮素以表观损失为主,施氮量高时大部分氮素残留于土壤剖面。     

Carbon dioxide flux and soil carbon stock as affected by crop residue management and soil texture in semi‐arid maize croplands in Tanzania

Crop residue management strategies must be adapted for improving carbon (C) balance and soil C stock in agroecosystems in sub‐Saharan Africa with consideration of the crop residue availability and site‐specific soil characteristics. We conducted field experiments to determine the effects of crop residue application method (incorporation/mulching) and quality (maize/cowpea) and N fertilizer application on the soil respiration rate and soil C stock in the surface soil layer (0–15 cm) in maize croplands with contrasting soil textures (clay/sandy) over 2 years from 2012 to 2014 in Tanzania. At the clay site, the incorporation of maize residues showed a 38% increase in CO₂ flux compared to mulching, whereas, at the sandy site, mulching showed a 16% increase compared to the incorporation. At the sandy site, mulching practice retained soil moisture content and apparently enhanced the decomposition of the original soil organic C in the surface layer. It is, therefore, suggested that mulching practice may accelerate a long‐term depletion of soil C stock at the sandy site. The cowpea residue incorporation led to rapid decomposition because of its high biodegradability at both sites. The N fertilizer application stimulated the decomposition of labile soil organic matter. The soil C stock in the surface layer did not significantly change after the 2‐year experiment, irrespective of crop residue treatment and soil type. In conclusion, adequate crop residue management in terms of suppressing CO₂ flux during a cropping season depends on soil type, but the long‐term effect on soil C stock is unclear.     

华北平原不同种植制度对粮食作物氮素利用和土壤氮库的影响

冬小麦-夏玉米一年两熟是华北平原粮食作物的主要种植制度,存在氮肥利用率低、土壤氮素过量累积问题。为探索华北平原氮素高效利用的适宜种植制度,采用15N示踪技术,基于3 a田间定位试验,对一年两熟冬小麦-夏玉米的常规水氮和优化水氮、两年三熟冬小麦-夏玉米-春玉米与冬小麦-夏大豆-春玉米及一年一熟春玉米3种种植制度的作物产量、15N利用率、氮素去向和土壤氮库表观平衡进行研究。结果表明,两年三熟的冬小麦-夏玉米-春玉米产量为32 248.52 kg/hm2,分别比一年两熟和一年一熟提高22.16%和52.88%;15N利用率为33.36%,比一年一熟提高26.12%。3种植制度的氮肥去向最高为土壤残留,其次为作物吸收和损失,两年三熟冬小麦-夏玉米-春玉米的作物吸氮量最高为151.82 kg/hm2,土壤氮库表观盈余量为21.22 kg/hm2,显著低于其他种植制度。综合分析,冬小麦-夏玉米-春玉米两年三熟在稳产高产和提高氮素利用率上具有可持续的潜力,是华北平原未来较为理想的种植制度。     

Maize grain production,plant nutrient concentration and soil chemical properties in response to different residue levels from two previous crops

ABSTRACT

The incorporation of previous crop residues in agricultural management benefits soil fertility, crop production, and environment. However, there is no enough information about maximum residue application level without negative effect over next crop yield. To evaluate maize (Zea mays L.) yield under short-time conservation management with incorporation and/or importation of different residue levels, a biannual rotation experiment was conducted in ash volcanic soil in south-central Chile. The experiment consisted of two previous crops, canola (Brassica napus L.) and bean (Phaseolus vulgaris L.), and four levels of residue incorporation (0%, 50%, 100%, and 200% of generated residue; from 0 to 21.4?Mg?ha^?1 for canola and from 0 to 19.0?Mg?ha^?1 for bean). Previous crop species and residue level affected some nutrients concentrations in grain and plant and some soil chemical properties, without effect in maize yield, which averaged 16.6?Mg?ha^?1. Bean residue increased Ca and reduced S in maize plant, increasing soil P, Ca, Mg and K (P?<?0.05). Maize grain Ca content was positively and proportionally affected by canola residue level and negatively and proportionally affected by bean residue level. All canola residue levels increased soil pH and Mg, but the highest level reduced soil S; soil P concentration increased proportionally with bean residue level. The highest bean residue level increased soil S. Different crop and levels of residue did not affect maize yield but did some plant nutrient concentration, and also affected some soil chemical properties.     

肥料配施枯草芽孢杆菌对夏玉米产量及养分利用的影响

目的枯草芽孢杆菌能增加土壤养分、改善土壤结构、提高化肥利用率,并能促使土壤中的有机质分解,促进作物生长,提高产量。研究枯草芽孢杆菌与肥料配施对夏玉米产量、肥料吸收利用的影响,为提高肥料的增产效果、降低农业面源污染提供理论指导。方法2016和2017年以登海605(DH605) 为试验材料,设置不施氮肥 (CK)、单施化肥 (N)、单施牛粪 (M)、牛粪 + 枯草芽孢杆菌 (MB)、化肥 + 枯草芽孢杆菌 (NB) 5个处理,分析了夏玉米产量和肥料吸收利用状况。结果牛粪配施枯草芽孢杆菌处理的籽粒产量及肥料利用效率最高,显著高于单施牛粪处理。与单施牛粪相比,牛粪配施枯草芽孢杆菌两年产量平均增幅为20.2%,植株氮、磷、钾积累量平均增幅分别为30.8%、63.5%、30.8%,肥料偏生产力平均提高20.7%;化肥配施枯草芽孢杆菌两年产量平均值比单施化肥提高2.55%,植株氮、磷、钾积累量平均增幅分别为12.5%、10.6%、3.84%,肥料偏生产力平均提高3.18%。牛粪配施枯草芽孢杆菌的经济效益比单施牛粪提高16.9%,化肥配施枯草芽孢杆菌的经济效益与单施化肥基本相同。分析表明,植株干物质积累量和氮素积累量,尤其是花后干物质和氮素积累的增加是增产增效的主要原因。其中牛粪配施枯草芽孢杆菌的效果要优于化肥配施枯草芽孢杆菌。结论肥料配施枯草芽孢杆菌能显著增加夏玉米的干物质积累量及产量,促进肥料的吸收利用。在施用氮肥的基础上,配施适量的枯草芽孢杆菌不仅能实现增产增效的目的,还能提高玉米的经济效益。有机肥配施枯草芽孢杆菌是实现夏玉米节肥增效的有效措施之一。     

不同氮源对中国稻田作物氮素营养的贡献

N availability is one of the most important factors limiting crop yield enhancement. The recovery of applications of ¹⁵N-labeled fertilizer and crop residues in a rice-wheat cropping system was determined for up to 6 consecutive growing seasons. The crop residues from the previous season were either incorporated or removed as two different treatments. Our results showed that 16. 55%-17.79% (17.17% on average) of the fertilizer N was recovered in the crop during the first growing season, suggesting that more than 80% of crop N was not directly from the N fertilizer. When ¹⁵N-labeled residues were applied, 12.01% was recovered in the crop in the first growing season. The average recoveries of fertilizer N and crop residue N in the soil after the first growing season were 33. 46% and 85. 64%, respectively. N from soil organic matter contributed approximately 83% of the N in the crop when ¹⁵N fertilizer was applied or 88% when crop residues were applied. There was a larger difference in the total ¹⁵N recovery in plant and soil between N applications in the forms of fertilizer and crop residues. Incorporation of crop residues following the ¹⁵N fertilizer application did not significantly promote ¹⁵N recovery in the crop or soil. On average, only additional 1.94% of N for the fertilizer-applied field or 5.97% of N for the crop residue-applied field was recovered by the crops during the 2nd and 3rd growing seasons. The total recoveries of ¹⁵N in crop and soil were approximately 64.38% for the fertilizer-applied field after 6 growing seasons and 79.11% for the crop residue-applied field after 5 growing seasons. Although fertilizer N appeared to be more readily available to crops than crop residue N, crop residue N replenished soil N pool, especially N from soil organic matter, much more than fertilizer N. Therefore, crop residue N was a better source for sustaining soil organic matter. Our results suggested that the long-term effect of fertilizer or crop residues on N recovery were different in the crop and soil. However, there was little difference between the practices of crop residue incorporation and residue removal following the N fertilizer application.     

低土壤肥力下秸秆还田和施钾对作物产量及土壤钾素平衡的影响

为了研究我国华北平原低肥力土壤条件下秸秆还田和施钾肥对作物产量和钾素平衡的影响,于2008年10月～2011年10月在中国农业科学院高新技术园区国家测土施肥中心实验室试验基地（河北省廊坊市）,通过3年6季的定位试验,比较了施钾与秸秆还田的增产效应、钾素吸收利用和作物土壤系统的钾素平衡状况。结果表明:在氮、磷肥充足的情况下,施用钾肥（NPK）、秸秆还田（NP+St）和秸秆还田配施钾肥（NPK+St）,均有明显的增产效应,表现为NPK+StNPKNP+StNP;不同施钾措施在夏玉米上的增产效果优于冬小麦;同一作物秸秆还田结合施钾肥的增产效果最好,降低了年度间的产量变异系数,在获得高产的同时,年际间产量稳定,有利于稳产;施钾肥和秸秆还田可显著提高小麦和玉米的钾素吸收总量; NPK+St、NPK、NP+St处理的钾素表观平衡系数分别为1.26,0.42,0.92。秸秆还田和施钾肥有利于钾素的收支平衡,减轻作物对土壤钾素的消耗,缓解土壤钾素肥力下降的程度,可维持土壤钾素肥力的稳定。     

低土壤肥力下施钾和秸秆还田对作物产量及土壤钾素平衡的影响

为了研究我国华北平原低肥力土壤条件下秸秆还田和施钾肥对作物产量和钾素平衡的影响,于2008年10月～2011年10月在中国农业科学院高新技术园区国家测土施肥中心实验室试验基地(河北省廊坊市),通过3年6季的定位试验,比较了施钾与秸秆还田的增产效应、钾素吸收利用和作物-土壤系统的钾素平衡状况。结果表明:在氮、磷肥充足的情况下,施用钾肥(NPK)、秸秆还田(NP+St)和秸秆还田配施钾肥(NPK+St),均有明显的增产效应,表现为NPK+St>NPK>NP+St>NP;不同施钾措施在夏玉米上的增产效果优于冬小麦;同一作物秸秆还田结合施钾肥的增产效果最好,降低了年度间的产量变异系数,在获得高产的同时,年际间产量稳定,有利于稳产;施钾肥和秸秆还田可显著提高小麦和玉米的钾素吸收总量;NPK+St、NPK、NP+St处理的钾素表观平衡系数分别为1.26、0.42、0.92。秸秆还田和施钾肥有利于钾素的收支平衡,减轻作物对土壤钾素的消耗,缓解土壤钾素肥力下降的程度,可维持土壤钾素肥力的稳定。     

不同耕作模式对稻田土壤理化性质及经济效益的影响

为研究不同耕作模式对土壤理化性状和作物经济效益的影响,对皖南地区4种典型耕作模式(单季稻种植、油稻轮作、麦稻轮作、烟稻轮作)的土壤和作物产量进行了研究。结果表明:与单季稻种植相比,轮作显著降低了土壤含水量;麦稻轮作和烟稻轮作土壤体积质量显著增加,孔隙度显著降低;麦稻轮作土壤有机质和碱解氮含量分别显著降低35.8%和47.8%;烟稻轮作土壤速效钾含量显著增加68.2%,速效磷含量提高109.5%。油稻轮作和烟稻轮作总产值比单季稻种植分别显著增加35.3%和155.5%。为解决轮作对土壤的不良影响,要注重增施有机肥和秸秆还田以改善土壤体积质量和孔隙度;麦稻轮作应重点解决土壤p H降低的问题;烟稻轮作要减少烟后晚稻的磷肥和钾肥施用量。总体而言,油稻轮作和烟稻轮作是皖南地区维护农田土壤肥力,促进农业可持续发展,实现农业增产增收的重要耕作模式。     

氮肥和接种根瘤菌对豌豆/玉米间作产量和水分利用效率的影响

豌豆/玉米间作是河西绿洲灌区面积最大的间作模式,也是当地重要的高产高效种植模式之一。针对目前氮肥过量施用和豆科作物生物固氮被忽视的实际,2011年和2012年在甘肃省武威市凉州区进行了豌豆/玉米间作大田试验,研究不同施氮量下,豌豆接种根瘤菌对豌豆/玉米间作体系作物籽粒产量和水分利用效率的影响,旨在为河西绿洲灌区豌豆/玉米间作体系节肥、高产的氮肥用量和接菌增产作用提供理论依据。结果表明:施用氮肥对豌豆产量影响不显著。接种根瘤菌后单作豌豆比不接菌处理两年平均增产12.7%,间作豌豆产量比单作两年平均增产61.1%,间作豌豆接种根瘤菌比不接菌两年平均增产4.8%。单作豌豆以施氮量75 kg(N)·hm-2接菌处理的产量最高,达到2 735 kg·hm-2;而且在此施氮量下接菌比不接菌两年平均增产达22.8%。施用氮肥对玉米的增产效果显著,施氮量在300 kg(N)·hm-2时单作玉米产量为14 394 kg·hm-2,间作比单作两年平均增产61.8%;间作豌豆带接菌较不接菌玉米两年平均增产3.3%。土地当量比在不同施氮量和接种根瘤菌的条件下都大于1。豌豆水分利用效率随施氮量增加而减小,最大值为不施氮的12.9 kg·mm-1·hm-2;玉米水分利用效率随施氮量增加先增大后减小,以施氮量300 kg(N)·hm-2处理为最高,达25.0 kg·mm-1·hm-2。综上所述,在豌豆/玉米间作体系中,玉米高产、高水分利用效率的施氮量为300 kg(N)·hm-2,豌豆高产高效的施氮量为75 kg(N)·hm-2。在大田生产中,接种根瘤菌对豌豆和玉米增产作用明显。     

土壤地力和长期施肥对潮土区小麦和玉米产量演变趋势的影响

为潮土区合理施肥管理提供依据,对32个长期定位点、24年（1987～2010）不施肥和化肥配施秸秆（农民常规施肥）处理的小麦和玉米产量及其与土壤地力和施肥量间的关系进行了分析。结果表明:潮土区土壤地力对小麦和玉米产量的平均贡献率分别为51.4%和54.0%,变异系数分别为39.0%和41.2%。不施肥处理小麦和玉米产量每年分别下降4.1 kg/hm2和96.6 kg/hm2;常规施肥处理的小麦和玉米每年分别增产61.5 kg/hm2和26.8 kg/hm2。施化肥量与作物增产量（常规施肥产量－不施肥产量）呈显著正相关。通过通径分析进一步证明,施氮量对小麦产量具有显著直接作用。同时,磷肥对提高小麦和玉米的产量具有重要作用。总之,在农民习惯耕作施肥管理水平下,潮土区不施肥处理的产量下降缓慢（含品种对产量的贡献）,常规施肥区产量表现出缓慢增加的趋势。     

河西绿洲灌区间作绿肥及其不同利用方式对玉米产量及土壤肥力的提升效应

[目的]研究玉米间作不同绿肥及绿肥不同利用方式在河西绿洲灌区的生产效益.[方法]田间定位试验始于2009年,该试验为河西绿洲灌区的典型种植模式,至取样时试验已进行12年.与玉米间作的绿肥作物包括针叶豌豆、甜豌豆、草木樨,每种绿肥均采用压青与根茬还田两种方式,以玉米单作为对照(CK).测定了玉米和绿肥生物量、产量构成因素...     

Arbuscular mycorrhizal fungus enhances crop yield and P-uptake of maize (Zea mays L.): A field case study on a sandy loam soil as affected by long-term P-deficiency fertilization

The P efficiency, crop yield, and response of maize to arbuscular mycorrhizal fungus (AMF) Glomus caledonium were tested in an experimental field with long-term (18-year) fertilizer management. The experiment included five fertilizer treatments: organic amendment (OA), half organic amendment plus half mineral fertilizer (1/2 OM), mineral fertilizer NPK, mineral fertilizer NK, and the control (without fertilization). AMF inoculation responsiveness (MIRs) of plant growth and P-uptake of maize were estimated by comparing plants grown in unsterilized soil inoculated with G. caledonium and in untreated soil containing indigenous AMF. Soil total P, available P, microbial biomass P, alkaline phosphatase activity, plant biomass, crop yield and total P-uptake of maize were all significantly increased (P < 0.05) by the application of OA, 1/2 OM, and NPK, but not by the application of NK. Specifically, the individual crop yield of maize approached zero in the NK-fertilized soils, as well as in the control soils. All maize plants were colonized by indigenous AMF, and the root colonization at harvest time was not significantly influenced by fertilization. G. caledonium inoculation increased mycorrhizal colonization significantly (P < 0.05) only with the NK treatment, and produced low but demiurgic crop yield in the control and NK-fertilized soils. Compared to the inoculation in balanced-fertilized soils, G. caledonium inoculation in either the NK-fertilized soils or the control soils had significantly greater (P < 0.05) impacts on soil alkaline phosphatase activity, stem length, plant biomass, and total P-uptake of maize, indicating that AMF inoculation was likely more efficient in extremely P-limited soils. These results also showed that balanced mineral fertilizers and organic amendments did not differ significantly in their effects on MIRs in these soils.