Re-defining tillage erosion: quantifying intensity–direction relationships for complex terrain

Abstract. Current tillage erosion models account for the influence of tillage direction in the magnitude of the soil (tillage) transport coefficient. It is argued here that this is counter-intuitive and causes significant problems in modelling tillage erosion in areas of complex terrain. This article examines whether a re-modelling of tillage erosion is possible that separates tillage direction (an interaction with the landform) from the soil transport coefficient (a measure of tillage intensity representing the combination of implement erosivity and soil erodibility). Experimental data for mouldboard ploughing upslope, downslope and cross-slope at Coombe Barton Farm, Devon are examined. Integration of data for all directions into a single relationship, which relates translocation in the direction of tillage to slope in the direction of tillage and translocation perpendicular to tillage to slope perpendicular to tillage, is not possible using previously published methods of analysis. However, when total translocation distance is regressed against the tangent of the slope at 45° to the tillage direction (bisecting the tillage direction and the direction of overturning) it is found that a single relationship can be used to describe tillage in all three directions. Therefore, this relationship is used to determine a single value of the soil transport coefficient ( k _fTa) for constant soil and implement conditions but different tillage directions. This redefinition of tillage is important both for true estimation of tillage erosion severity, the adirectional coefficient being 40% larger than the directional coefficient, and for modelling of tillage erosion in complex terrain. These improvements are vital when tillage erosion simulation is used to direct soil conservation strategies.     

The effects of stubble burning and tillage on soil carbon sequestration and crop productivity in southeastern Australia

Abstract. In Australia, stubble burning and tillage are two of the major processes responsible for the decline of soil organic carbon concentration in cropped soils, and the resulting soil degradation. However, the relative importance of these two practices in influencing the soil organic carbon concentration and the long-term impact on soil quality and productivity are not clear. The effects of stubble burning as practised by farmers in southeastern Australia were evaluated in two field trials, one of 19 years duration, the other of 5 years. Conventional tillage (three tillage passes) led to greater loss of soil organic carbon than stubble burning. Loss of total soil organic carbon attributed to stubble burning in the 0–10 cm layer was estimated to be 1.75 t C ha⁻¹ over the period of the 19-year trial, equivalent to 29% of that lost due to tillage. In the 5-year trial, no change in soil organic carbon due to stubble burning was detectable. Changes in soil quality associated with stubble burning detected in the longer trial included a reduction in macro-aggregate stability, and increases in pH and exchangeable K⁺. Only the latter two were detected in the shorter trial. A higher mean wheat yield (average 0.15 t ha⁻¹) following stubble burning was observed in the 19-year trial but not in the 5-year trial. Research to monitor the longer term effects of stubble burning is needed, and to identify conditions where loss of soil organic carbon is minimized.     

Simulating evolution of glyphosate resistance in Lolium rigidum II: past, present and future glyphosate use in Australian cropping

Glyphosate is a key component of weed control strategies in Australia and worldwide. Despite widespread and frequent use, evolved resistance to glyphosate is rare. A herbicide resistance model, parameterized for Lolium rigidum has been used to perform a number of simulations to compare predicted rates of evolution of glyphosate resistance under past, present and projected future use strategies. In a 30‐year wheat, lupin, wheat, oilseed rape crop rotation with minimum tillage (100% shallow depth soil disturbance at sowing) and annual use of glyphosate pre‐sowing, L. rigidum control was sustainable with no predicted glyphosate resistance. When the crop establishment system was changed to annual no‐tillage (15% soil disturbance at sowing), glyphosate resistance was predicted in 90% of populations, with resistance becoming apparent after between 10 and 18 years when sowing was delayed. Resistance was predicted in 20% of populations after 25–30 years with early sowing. Risks of glyphosate resistance could be reduced by rotating between no‐tillage and minimum‐tillage establishment systems, or by rotating between glyphosate and paraquat for pre‐sowing weed control. The double knockdown strategy (sequential full rate applications of glyphosate and paraquat) reduced risks of glyphosate and paraquat resistance to <2%. Introduction of glyphosate‐resistant oilseed rape significantly increased predicted risks of glyphosate resistance in no‐tillage systems even when the double knockdown was practised. These increased risks could be offset by high crop sowing rates and weed seed collection at harvest. When no selective herbicides were available in wheat crops, the introduction of glyphosate‐resistant oilseed rape necessitated a return to a minimum‐tillage crop establishment system.     

不同耕作措施下旱地春小麦田和豌豆田的蒸发蒸腾特性及产量效应

为探明土壤水对旱地作物产量形成的有效性,通过田间定位试验研究了不同耕作措施下旱地农田蒸发蒸腾特性及产量效应。结果表明:免耕秸秆覆盖(NTS)能够增加作物生长期间总蒸散量(ET),麦-豆和豆-麦两种轮作序列下春小麦田和豌豆田的总蒸散量均表现为免耕秸秆覆盖(NTS)>传统耕作(T)>免耕(NT)>传统耕作加秸秆覆盖(TS)。传统耕作土壤棵间蒸发量(E)均高于保护性耕作,春小麦田的土壤棵间蒸发量表现为TS>T>NT>NTS,棵间蒸发量占总蒸散量的比率(E/ET)依次为53.8%,48.8%,37.2%,34.9%;豌豆田棵间蒸发量表现为T>TS>NTS>NT,棵间蒸发量占总蒸散量的比率依次为44.1%,40.9%,35.1%,33.3%。蒸散量及腾发比与产量和WUE在其主要受影响的月份呈正相关关系,且产量与WUE随蒸散量与腾发比的增加而增加。     

犁体耕作阻力模型仿真分析与试验研究

为进一步提高犁体耕作性能,分析影响犁体耕作阻力的因素,基于摩尔-库仑土壤剪切理论,建立了包含犁体结构参数、土壤物理特性和犁体工作参数的耕作阻力模型,耕作阻力表达式包含了犁铲尖和犁铧切削土壤阻力、土壤在犁壁上产生的摩擦力和翻垡过程土壤动量变化产生的阻力、犁壁翻垡使土壤势能增加产生的阻力、作用在犁铧和犁壁上的横向力产生的摩擦力、土壤横向运动对犁壁产生的阻力。基于新疆玉米地土壤物理特性,建立了两种高速犁体A和B的耕作阻力方程,在不同耕宽（0.35、0.42 m）、耕深（0.255、0.305 m）和耕速(2.22、2.5、2.78 m·s^-1)作业条件下对耕作阻力进行了理论、仿真和试验研究,分析了犁体耕作阻力的影响因素,结果表明,仿真值与计算值的平均误差为3.37%,试验值与计算值的平均误差为7.18%,试验值与仿真值的平均误差为3.71%。犁体耕作阻力与铧刃角呈非线性增长关系;与耕深呈三次函数增长关系;与耕速呈二次函数增长关系;犁体耕作过程的功率消耗与耕速呈三次函数的增长关系。提出设置合理的安全系数（s_f）,使拖拉机配套功率P_s     

不同灌水水平下少耕地膜覆盖对玉米农田土壤温度和水分利用效率的影响

以大田玉米为研究对象,在少耕地膜覆盖和不同灌水水平下,研究了一膜两年用地膜覆盖、秋免耕春覆膜和传统耕作覆膜对玉米农田土壤温度和水分利用效率(WUE)的影响。结果表明:与传统耕作覆膜和秋免耕春覆膜两种新膜覆盖处理相比,一膜两年用处理在玉米播种到拔节期的增温效果显著低于新膜覆盖,农田0~25 cm土壤平均温度较传统覆膜处理低13.35%,而对玉米拔节期到成熟期的土壤温度无明显影响,且农田0~25 cm土层土壤积温差异也不显著,相同覆膜方式下不同灌水水平间有显著差异,随着灌水水平的降低土壤积温增加;一膜两年用地膜覆盖方式下玉米籽粒产量和WUE与两种新膜覆盖方式相当,中灌水水平下WUE最高,达到17.89kg·mm-1,且在低灌水水平下获得籽粒产量显著高于传统覆膜处理,一膜两年用覆盖、灌溉定额5 700 m3·hm-2较传统耕作覆膜、灌水定额5 700 m3hm-2处理的玉米产量高出16.39%。说明,一膜两年用地膜覆盖在玉米播种到拔节期的增温效应低于新膜覆盖,但并不影响籽粒产量的形成,且在存在水分胁迫的低灌水水平下一膜两年用覆盖模式可减缓干旱胁迫,提高作物籽粒产量,是适于西北绿洲灌区的具有较好经济效益和生态效益的覆膜农田管理新技术。     

民勤绿洲灌区保护性耕作对土壤风蚀与土壤物理性质的影响

通过春小麦田间试验,以传统耕作为对照,分析免耕不覆盖、免耕秸秆覆盖、立茬和残茬压倒4种保护性耕作措施田间输沙量、土壤团聚体、<0.01 mm物理性黏粒、<0.01 mm分散性黏粒和分散系数随年限增加的变化,研究民勤绿洲灌区保护性耕作对土壤风蚀与土壤物理性质的影响。结果表明:与传统耕作相比,保护性耕作输沙量显著减少;>1 mm团聚体作为不可风蚀颗粒的数量没有发生显著变化,保护性耕作大团聚体(>0.25 mm)含量有增大趋势、微团聚体(0.25～0.05 mm)含量有减少趋势;保护性耕作实施2年后,<0.05 mm土粒含量占比除立茬处理减少不显著外,其他保护性耕作处理均显著减少;试验第3年,传统耕作处理<0.01mm物理性黏粒含量较保护性耕作处理有减少趋势;免耕不覆盖、立茬和残茬压倒处理<0.01 mm分散性黏粒含量随年限的增加显著下降,免耕秸秆覆盖处理变化不显著;免耕不覆盖和残茬压倒处理土壤分散系数随年限的增加显著下降,免耕秸秆覆盖和立茬处理下降不显著;保护性耕作实施的第3年,各保护性耕作处理分散系数出现减小的趋势。输沙量与>1 mm团聚体...     

耕作方式对小麦耗水特性和籽粒产量的影响

【目的】利用测墒补灌技术确定灌水量,研究高产条件下耕作方式对小麦的耗水特性、蒸腾速率及籽粒产量的影响,为小麦节水高产栽培提供理论依据。【方法】2007—2008年和2008—2009年小麦生长季,在高肥力条件下,设置条旋耕、深松+条旋耕、旋耕、深松+旋耕和翻耕5种耕作方式,研究不同处理对小麦耗水量、旗叶蒸腾速率、叶片水分利用效率、籽粒产量和水分利用效率的影响。【结果】深松+旋耕处理的总耗水量最高,深松+条旋耕和翻耕处理次之,且两者无显著差异,条旋耕和旋耕处理低于上述处理,表明深松后小麦的总耗水量增加。深松+条旋耕处理的土壤贮水消耗量占总耗水量的比例和开花至成熟阶段的耗水量及其模系数最高,深松+旋耕处理次之,条旋耕和旋耕处理均低于翻耕处理,表明深松+条旋耕促进了土壤贮水的消耗,提高了小麦灌浆阶段的耗水量,有利于籽粒灌浆。深松+条旋耕和条旋耕处理的灌水量占总耗水量的比例低于其它处理,条旋耕处理最低,深松+旋耕和翻耕处理最高且两者无显著差异,旋耕处理次之。灌浆中后期,深松+条旋耕和深松+旋耕处理的叶片水分利用效率最高且两者无显著差异,翻耕处理次之,条旋耕和旋耕处理低于上述处理,表明深松有利于小麦在灌浆中后期保持较高的光合能力。深松+条旋耕和深松+旋耕处理的籽粒产量最高且两者无显著差异,翻耕处理次之,条旋耕和旋耕处理低于上述处理,表明深松有利于籽粒产量的提高。深松+条旋耕处理的水分利用效率和灌溉效益最高,深松+旋耕处理次之,条旋耕和旋耕处理低于翻耕处理,表明深松+条旋耕有利于水分的高效利用。【结论】本试验条件下,深松+条旋耕是兼顾高产节水高效的耕作方式。     

保护性耕作模式对黑土有机碳含量和密度的影响

以公主岭市长期（10 a）保护性耕作定位试验为研究对象,分析与传统耕作模式相比的几种保护性耕作模式对黑土固碳效应的影响。共设4种耕作模式,即秋翻秋耙匀垄、秋灭茬匀垄、全面旋耕深松和宽窄行交替休闲（又叫松带、苗带交替休闲）（后3种视为保护性耕作）。结果表明,经过10 a的耕作试验,不同的耕作模式对土壤有机碳有显著的影响。表层0～20 cm秋翻秋耙匀垄和秋灭茬匀垄模式的土壤有机碳含量最低,深层30～50 cm全面旋耕深松模式的土壤有机碳质量分数显著低于其他耕作模式13.49%～25.14%;0～50 cm耕层     

深松作业效果试验及评价方法研究

【目的】分析单、双铲深松作业效果及评价方法,为提高耕作质量和减少能源消耗的深松作业提供决策依据。【方法】以箭形深松铲为对象,在模拟大田土壤环境的基础上,利用室内土槽研究了单、双铲深松作业效果及评价方法,提出了土壤硬度变化系数、土壤体积膨松系数、单位松土带宽度耕作阻力系数和土壤相互扰动系数等4个评价指标。【结果】(1)单、双铲深松作业后的平均土垄高度差分别为7.342cm和6.492cm,双铲比单铲的平均土垄高度差减少11.58%,说明双铲深松后的地表平整性优于单铲,且深松铲间距是影响土壤体积膨松程度的主要因素,其对深松后土壤形成的垄形与坑形有重要影响;(2)在土壤扰动区域内,当深松深度为3~17cm时,双铲作业的土壤硬度变化程度较单铲显著,当深度为17~30cm时,单铲作业的土壤硬度变化程度大于双铲;(3)深松单位松土带宽度时,双铲的平均耕作阻力为单铲的0.668倍,较单铲减少69.31N,双铲的能耗较单铲减少33.2%;(4)双铲的土壤相互扰动系数为1.170,深松铲布局方式对土壤扰动有重要影响。【结论】本研究结果有利于深入理解单、双铲的深松作业效果,促进符合节能减阻要求的深松机具的研发及田间作业机器系统的优化选用。