Morphology and distribution of wheat and maize roots as affected by tillage systems and soil physical parameters in temperate climates: an overview

Congregated information on maize and wheat root morphology and their distribution as influenced by tillage and soil physical conditions is meager. Root growth under no-tillage (NT) or conventional tillage (CT) is variable: Under NT, higher bulk density slows root elongation and provides shorter roots but simulate root branching; results may be opposite depending on soil texture. Under CT, soil compaction may have negative effects on root growth, with roots exhibiting plasticity. In humid climates, low soil temperatures can reduce root length density (RLD) and increase the diameter of spring cereals under NT. Tillage intensity induces a different distribution of nutrients, a trend which increases with time resulting in higher RLD in the topmost layer of NT. Compared to maize it is difficult to present an overview of the effect on tillage on the RLD of wheat due to inconclusive results. Adequate placements of banded starter fertilizer will effectively build up an early root system of maize, especially at suboptimal growth temperatures. Many studies reported a higher or similar grain yield of maize or wheat under NT compared to CT in temperate climates. However, the limited information or the conflicting results will promote the topic for inclusion in future breeding programs.     

基于Meta-analysis的中国北方地区免耕玉米产量效应研究

【目的】定量分析免耕对中国北方地区玉米产量的时空效应和影响机制,为该地区免耕的科学应用和推广提供依据。【方法】以中国北方为研究区域,以传统耕作为对照,通过检索文献整合已发表的相关田间试验数据（截止2017年4月共获得68篇文献和82组试验数据,将数据按照区域（东北、华北和西北）、年降水量（＜500 mm和≥500 mm）、年均气温（＜10℃和≥10℃）、耕作模式（平作和垄作）、种植制度（连作和轮作）、是否秸秆还田、试验年份（2000年之前、2000-2009年和2010年之后）和免耕持续年限（1-2 a、3-5 a、6-9 a和≥10 a）进行分组）,利用Meta-analysis方法系统探究免耕对玉米产量的时空效应与影响因素。具体分析过程包括异质性检验、综合效应量计算、发表偏倚检验、敏感性分析、累积Meta-analysis和亚组分析（影响因素分析）。【结果】与传统耕作相比,免耕总体上可显著提高玉米产量,平均增产率为3.1%（置信区间0.7%-5.5%,数据不存在发表偏倚和极端值）。2000年之前,免耕的累积增产效应不稳定（平均-0.7%-6.6%）;2000年之后,免耕与传统耕作的累积产量差异逐渐由不显著变为显著。在东北地区,免耕表现出显著的增产效应（平均5.3%,置信区间1.5%-9.2%）;而在华北和西北地区,免耕的增产效应不显著,分别为-2.6%-6.4%和-1.0%-6.4%。在年降水量＜500 mm、年均气温＜10℃的地区和轮作、秸秆还田条件下,免耕的增产率显著提高,平均分别为5.4%（置信区间1.7%-9.1%）、3.8%（置信区间0.8%-6.7%）、4.4%（置信区间1.3%-7.5%）和3.3%（置信区间0.8%-5.8%）。平作和垄作下,免耕的增产效应均不显著。2010年之后,免耕的增产效应显著提高（平均6.1%）,且变幅较小（2.5%-9.7%）。随着免耕持续年限的延长,玉米增产率呈先增加后降低的趋势,当持续3-5 a时,免耕的增产效应显著且达到峰值（平均3.8%,置信区间1.6%-6.0%）。【结论】在年降水量较少或年均气温较低的区域,轮作或秸秆还田条件下,有利于发挥免耕的增产效应;东北地区较华北和西北地区更适宜免耕;3-5 a为较合理的免耕持续年限。     

A Rapid Chemical Method for Estimating Potentially Mineralizable and Particulate Organic Nitrogen in Mollisols

The objective of this study was to obtain an indicator of labile nitrogen (N) through a cost- and time-saving procedure by evaluating the relationships among potentially mineralizable N (N₀), particulate organic matter N (POM-N) and soil organic N extracted through partial soil digestion with different concentrations of sulfuric acid (H₂SO₄). Soil sampling (0–20 cm) was from nine fields under no-tillage. The N₀ and POM-N were determined by long-term aerobic incubation and soil physical fractionation, respectively. A simple chemical method was developed by soil digestion at 100°C for 4 h with different concentrations of H₂SO₄ (0.1, 0.5, 1, 6, 12, and 24 mol L^?1). All acid concentrations showed significant relationships with N₀ as POM-N; however, the best prediction was resulted for 0.5 mol L^?1 (R² = 0.90–0.94, respectively), thus using this methodology as soil labile N indicator. This method would optimize N₀ and POM-N estimation in short term and at a low cost.     

轮耕对双季稻田耕层土壤有机碳储量的影响

【目的】针对南方稻田连续免耕存在的有机碳表层富集现象,进行土壤轮耕效应的初步研究。【方法】试验选择双季稻区连续免耕7年稻田,研究了轮耕对耕层土壤有机碳含量及其对等质量法计算的耕层土壤有机碳储量影响。【结果】长期免耕后,翻耕、旋耕降低了表层0—5cm土壤有机碳含量,提高了下层5—20cm土壤有机碳含量,进而降低了耕层土壤有机碳层化率;而翻耕、旋耕后免耕土壤有机碳含量相对于翻耕、旋耕分别呈相反的趋势。2006—2009年表层600Mg·hm-2土壤有机碳储量均以长期免耕最高。长期免耕后,翻耕、旋耕秸秆还田会提高下层土壤有机碳储量,进而在一定程度上影响耕层2550Mg·hm-2土壤有机碳的累积;而翻耕、旋耕后免耕耕层土壤有机碳储量较翻耕、旋耕有所降低。【结论】长期免耕后,连续免耕秸秆还田会增加表层600Mg·hm-2土壤有机碳储量;而翻耕、旋耕秸秆还田会提高下层土壤有机碳储量。     

旱地春玉米倒秆免耕两元带状覆盖膜侧种植技术与应用前景

为了将有限的自然降水最大限度地蓄积、保存于土壤之中,并尽可能地提高其利用效率,连续多年采用田间试验与大面积示范相结合的方法,集成创新研究的"旱地春玉米倒秆免耕两元带状覆盖膜侧种植技术",融"冬闲期倒秆覆盖免耕"与"生育期两元带状覆盖膜侧种植"两项技术的优点于一体,能综合调节旱作农田的水、肥、气、热条件,最大限度地利用自然降水,因而旱地春玉米生长稳健茁壮,增产增收效果显著,水分利用率也达最高。同时,该技术并具有增加土壤有机质,提高土壤潜在肥力和控制水土流失,减轻沙尘飞扬,改善生态环境,促进农业可持续发展的效果。     

早稻免耕抛秧与全翻耕抛秧对比试验

为推广水稻免耕栽培技术提供依据,进行了早稻免耕抛秧与全翻耕抛秧对比试验。结果表明,免耕抛秧与全翻耕抛秧相比,有效穗有所增加,结实率提高2.7%,但每穗总粒数和千粒重会有所下降,产量增加405kg/hm2,每公顷可节支增收1179.00元。文中还讨论了免耕抛秧栽培的关键技术。     

免耕稻田纹枯病越冬菌核量调查方法比较

根据免耕稻田纹枯病菌核在田间的分布特点,对纹枯病菌核量田间调查方法进行了改进。试验分别对15块免耕稻田采用传统的土壤淘洗法和直接观测法进行纹枯病越冬菌核量调查,结果表明,直接观察法测得的菌核数量远多于土壤淘洗法测得的数量,并且在省时、省力的同时也使调查结果更加真实可靠。因此,直接观察法更加适用于免耕稻田纹枯病越冬菌核数量的调查。     

旱地马铃薯免耕覆盖摆种的产量表现及其对土壤水分和养分的影响

设计实施了黄土高原西部旱农区马铃薯传统耕作和5种免耕覆盖耕作措施的大田对比试验,对不同耕作措施下的马铃薯产量、水分利用效率、各层次土壤水分、有机质含量以及养分含量进行了研究.结果表明:免耕秸秆覆盖除垄上秸秆覆盖摆种外,其它各处理的产量和水分利用效率较传统耕作都有不同程度的提高;免耕秸秆覆盖能明显改善0～80cm的土壤贮水量,尤其是0～30cm的土壤贮水量;免耕秸秆覆盖可以提高0～30cm土壤层的有机质,但是对养分总量平衡的影响不大.     

免耕半固态直播对水稻的生长及产量构成的影响

以水稻中早39为材料,采用免耕半固态直播(破胸稻种与稀泥以一定比例混合,播种在免耕的稻田里,NS),以传统直播为对照(CK),通过测定单株地上部干物质积累量、分蘖动态变化、SPAD值和叶绿素含量等,研究免耕半固态直播对水稻生长及产量构成的影响。结果表明:在三叶期和分蘖期,2个处理的单株地上部分干物质积累量差异没有统计学意义,但孕穗期和齐穗期NS处理的单株地上部干物质积累量分别为7.84、14.45 g,与CK相比,差异均达到极显著水平;NS处理的单株分蘖数为2.67,CK处理的单株分蘖数为2.56,两者的差异无统计学意义;在抽穗期,NS处理植株的倒二叶SPAD值达到最大,为46.90,与CK比较,差异极显著;9月9日,NS处理植株的剑叶SPAD值、叶绿素a和叶绿素b含量均出现最大值,SPAD值为45.96,叶绿素a和叶绿素b分别为6.38、2.24 mg/L;NS和CK处理的产量分别为7.31、6.94 t/hm2,差异达显著水平。     

Long-Term Sulfur Fertilization: Effects on Crops and Residual Effects in a No-Till System of Argentinean Pampas

A long-term experiment has been conducted between 2001 and 2008 at Balcarce, Argentina, to determine the effect of sulfur (S) fertilization on S concentration in grains, crop yield, and residual S in soil. Two treatments were evaluated: annual S application to crops (15 kg ha^?1; S1) and a control with no S fertilization (S0). Sulfur fertilization only increased wheat yield (22% of the crops in the experiment). However, S application increased S concentration in grains in wheat, soybean, and maize (56% of the crops). Although, for all years, the S mass balance was positive for S1 and negative for S0, no differences in soil S extracted as sulfate (S-SO₄ ^?2) content previous to the crop sown were determined. The absence of differences in S accumulation in aboveground vegetative biomass and grain of the maize used as a check also suggest that long-term S fertilization did not affect the soil S availability for crops.