轮耕秸秆还田促进冬小麦干物质积累提高水氮利用效率

通过田间定位试验,探究了不同耕作措施及秸秆还田对2015-2017年2个生长季冬小麦物质积累、氮素积累及水氮利用效率的影响。采用2因素裂区试验设计,主区为秸秆还田(S)和秸秆不还田(NS);副区分别为深耕(DT)、轮耕(RT)和免耕(NT)处理。结果表明:S处理较NS处理显著增加冬小麦旗叶SPAD和光合速率,提高成熟期植株生物量,但产量增加不显著。RT处理于2015-2016年和2016-2017年较DT处理分别显著增产4.88%和9.05%,2016-2017年较NT处理显著增产3.64%。秸秆还田和耕作方式交互作用显著影响冬小麦产量,S+RT处理2015-2016年和2016-2017年较NS+DT处理分别显著提高8.68%和16.98%。S处理显著增加植株氮素积累量和水分利用效率;RT处理显著提高冬小麦水分利用效率,增加冬小麦氮素积累量、籽粒氮素积累量、氮素转运及其利用效率。2015-2016年和2016-2017年RT处理水分利用效率较NT处理分别提高8.45%和8.92%,2015-2016年较DT处理提高5.24%;2016-2017年RT处理氮肥偏生产力较NT和DT处理分别显著提高3.68%和9.16%;氮素籽粒生产效率较NT和DT处理分别显著提高10.60%和4.78%。S+RT处理花后SPAD下降幅度最小,花期和成熟期均具有较高的光合速率,产量、水分利用效率和氮肥偏生产力与NS+DT和S+DT相比分别平均提高了12.58%,8.53%,7.95%和4.11%,19.79%,11.44%。因此,秸秆还田配合轮耕措施是黄淮海南部较为适宜的节水省肥型冬小麦耕作栽培措施。     

Twenty years of conservation tillage research in subarctic Alaska: II. Impact on soil hydraulic properties

Soil management practices are needed in the subarctic that stabilize the soil against the forces of wind and water as well as conserve soil water for crop production. There is a paucity of information, however, regarding the long-term effects of conservation tillage on soil hydraulic properties in subarctic Alaska. The objective of this study was therefore to characterize infiltration, water retention, and saturated hydraulic conductivity of a soil 20 years after establishing tillage and straw management treatments in interior Alaska. The strip plot experimental design, established on a silt loam and maintained in continuous barley (Hordeum vulgare L.), included tillage as the main treatment and straw management as the secondary treatment. Tillage treatments included no tillage, autumn chisel plow, spring disk, and intensive tillage (autumn and spring disk) while straw treatments included retaining or removing stubble and loose straw from the soil surface after harvest. Soil properties were measured after sowing in spring 2004; saturated hydraulic conductivity was measured by the falling-head method, infiltration was measured using a double-ring infiltrometer, and water retention was assessed by measuring the temporal variation in in-situ soil water content. No tillage resulted in greater saturated hydraulic conductivity and generally retained more water against gravitational and matric forces than other tillage treatments. Infiltration was greater in autumn chisel plow than other tillage treatments and was presumably suppressed in no tillage by an organic layer overlying mineral soil. Infiltration was also enhanced by retaining straw on rather than removing straw from the soil surface after harvest. No tillage is not yet a sustainable management practice in this region due to lack of weed control strategies. In addition, the formation of an organic layer in no tillage has important ramifications for the soil hydrological and thermal environment. Therefore, minimum tillage (i.e., autumn chisel plow or spring disk) appears to be a viable management option for maximizing infiltration in interior Alaska.     

科学耕作与留茬改良小麦-玉米两熟农田土壤物理性状及增产效果

为了探讨不同覆盖耕作方式对农田土壤物理性状及作物产量的影响,该试验研究了免耕、常规2种耕作方式和4种留茬高度的玉米秸秆还田处理,对麦-玉两熟农田土壤含水率、容重、孔隙度以及作物产量的影响。结果表明:在0～40cm土层内,秸秆还田的集雨和保水效果显著,免耕留茬0.5m还田处理的含水率比免耕无覆盖处理增加了15.95%。秸秆还田量对0～40cm内土壤贮水量的影响不同。耕作措施显著影响了土壤容重,小麦播种前常规留茬1m还田、常规全量还田处理容重低至1.0g/cm3左右。秸秆还田能增加土壤总孔隙度、降低毛管与非毛管孔隙度的比值。单一免耕处理降低了作物产量,而免耕覆盖能增产,其留茬1m还田处理比无还田处理增产22.44%,比常规留茬0.5m还田处理高3.64%。因此,免耕留茬1m还田处理在改善农田土壤物理性状和增加作物产量方面显著,该研究可为农田管理过程中耕作措施和秸秆还田量的选择提供参考依据。     

Twenty years of conservation tillage research in subarctic Alaska: II. Impact on soil hydraulic properties

Soil management practices are needed in the subarctic that stabilize the soil against the forces of wind and water as well as conserve soil water for crop production. There is a paucity of information, however, regarding the long-term effects of conservation tillage on soil hydraulic properties in subarctic Alaska. The objective of this study was therefore to characterize infiltration, water retention, and saturated hydraulic conductivity of a soil 20 years after establishing tillage and straw management treatments in interior Alaska. The strip plot experimental design, established on a silt loam and maintained in continuous barley (Hordeum vulgare L.), included tillage as the main treatment and straw management as the secondary treatment. Tillage treatments included no tillage, autumn chisel plow, spring disk, and intensive tillage (autumn and spring disk) while straw treatments included retaining or removing stubble and loose straw from the soil surface after harvest. Soil properties were measured after sowing in spring 2004; saturated hydraulic conductivity was measured by the falling-head method, infiltration was measured using a double-ring infiltrometer, and water retention was assessed by measuring the temporal variation in in-situ soil water content. No tillage resulted in greater saturated hydraulic conductivity and generally retained more water against gravitational and matric forces than other tillage treatments. Infiltration was greater in autumn chisel plow than other tillage treatments and was presumably suppressed in no tillage by an organic layer overlying mineral soil. Infiltration was also enhanced by retaining straw on rather than removing straw from the soil surface after harvest. No tillage is not yet a sustainable management practice in this region due to lack of weed control strategies. In addition, the formation of an organic layer in no tillage has important ramifications for the soil hydrological and thermal environment. Therefore, minimum tillage (i.e., autumn chisel plow or spring disk) appears to be a viable management option for maximizing infiltration in interior Alaska.     

稻麦两熟条件下不同土壤耕作方式与秸秆还田效用分析

该文通过大田小区和网室水泥池微区的3年定位试验，比较研究了稻麦两熟条件下免耕秸秆覆盖、免耕高茬、翻耕秸秆还田(秸秆稻季翻埋麦季覆盖)、翻耕(对照，CK)4个处理对土壤理化性质和稻麦产量的影响，从土壤管理技术方面探讨了不同耕作方法与秸秆直接还田在稻麦两熟地区的应用效果。结果表明：免耕使土壤容重和穿透阻力增加，而秸秆还田可改善土壤结构，提高土壤养分含量，翻耕还田3年后土壤有机质、全氮、速效磷、速效钾含量比对照分别增加4.7%～13.0%、0%～10.6%、0.2%～10.6%、8.4%～15.5%。麦季秸秆还田的产量有增有减，实际产量免耕覆盖还田略低，对照的产量较高，秸秆还田平均减产1%左右；而水稻翻耕秸秆还田的产量最高，比对照平均增产3%左右。因此，在稻麦两熟条件下，从省工节本和提高地力角度可采用稻麦免耕秸秆覆盖与留高茬还田，从提高产量和地力角度宜采用稻季翻耕秸秆还田。     

不同耕作方式与秸秆还田周年生产力的综合评价(简报)

该文通过3 a的定位试验,比较研究了稻麦两熟条件下免耕套种秸秆覆盖、免耕套种高茬、翻耕秸秆还田、翻耕秸秆不还田（对照,CK）4个处理对周年生产力的影响。结果表明：免耕套种的小麦产量降低,水稻产量增加,年产量略降,翻耕秸秆还田具较高产量生产力。如考虑节省的秧田种植小麦,则免耕套种的稻麦年产量可与翻耕秸秆还田持平。经技术经济分析,采用稻麦免耕套种秸秆还田,具有明显的节本增收、提高活劳动净产率的效果,在稻麦周年产量不减的同时,比翻耕秸秆不还田处理增收1874.8元/hm2,增加18.0%,经济生产力最高。翻耕秸秆还田比不还田有一定的增产增收效果,如果考虑到耕地持续生产力,秸秆还田后所带来的土壤肥力效应和减少肥料用量,其增产增收效果更为明显。从高产、高效、可持续发展等方面,运用综合评分法对稻麦两熟制不同耕作栽培方式周年生产力综合评价,免耕套种秸秆还田得分最高,周年生产力最好,免耕套种高茬和翻耕秸秆还田居中,翻耕秸秆不还田得分最低,周年生产力最差。     

Tillage and straw management for modifying physical properties of a subarctic soil

Conservation tillage practices are intended to minimize soil erosion. Yet little is known concerning changes in physical properties of subarctic soils subject to tillage practices. This study ascertained whether physical properties of a newly cleared subarctic soil are altered after 7 years of continuous barley (Hordeum vulgare L.) using different tillage and straw management strategies. Tillage and straw treatments were established in 1983 near Delta Junction, Alaska, and consisted of conventional fall and spring disk, fall chisel plow, spring disk, and no-tillage. Tillage plots were split by straw management practices, which included straw and stubble, stubble only, and no straw or stubble. Soil samples were collected from the upper 0.15 m of the profile in the spring of 1990 to assess water content, bulk density, saturated hydraulic conductivity, dry aggregate and mechanical stability, penetration resistance, water retention, and particle size distribution. Percent non-erodible aggregates, mechanical stability, and penetration resistance were greater for no-tillage compared to conventional tillage, chisel plow, and spring disk. No-tillage soils were also typically wetter, denser, and had a greater hydraulic conductivity. The spring disk treatment was least susceptible to erosion and also conserved soil water compared with chisel plow. Straw maintained on the surface conserved water and promoted soil stability.     

绿洲灌区小麦免耕秸秆还田对后作玉米产量性能指标的影响

产量性能是决定作物生长发育和产量形成的关键因素,研究前茬秸秆处理方式对后茬作物产量性能指标的影响,对于建立高效种植制度、优化栽培措施具有重要指导意义。2009—2012年,在甘肃河西绿洲灌区,通过田间定位试验,研究了前茬小麦不同秸秆还田和耕作措施(NTSS:25 cm高茬收割立茬免耕;NTS:25 cm高茬等量秸秆覆盖免耕;TIS:25 cm高茬等量秸秆翻耕;CT:不留茬翻耕对照)对后作玉米产量性能指标的影响,以期为优化试区玉米种植模式提供依据。结果表明,与CT相比,前茬小麦秸秆还田降低了后作玉米大喇叭口期之前的叶面积指数(LAI)与光合势(LAD),但增大了吐丝期之后的LAI与LAD,延缓了衰老,以NTSS、NTS延缓衰老作用突出;NTSS、NTS和TIS处理玉米全生育期的平均叶面积指数(MLAI)比CT分别提高12.8%、19.1%和7.0%,总光合势分别提高12.9%、18.6%和6.8%,免耕秸秆还田(NTSS和NTS)提高MLAI和LAD的效果最好。免耕秸秆还田提高了玉米全生育期的平均净同化率(MNAR),以NTSS提高作用明显,较CT高10.7%;但净同化率(NAR)表现为吐丝期之前增大,吐丝期之后降低。NTSS、NTS提高了后作玉米的籽粒产量,比CT分别高13.0%、15.6%,TIS比CT提高7.9%,NTS增产效应最大。不同秸秆还田及耕作方式下,玉米籽粒产量与MLAI、穗数(EN)、穗粒数(KNE)呈极显著正相关性,与收获指数(HI)呈显著正相关性,但与MNAR无显著相关性。MLAI、EN、KNE增加、HI提高是前茬小麦免耕秸秆还田提高后作玉米产量的主要原因。前茬秸秆免耕还田优化后茬玉米主要产量性能指标的效果最好。因此,前茬小麦25 cm秸秆覆盖免耕还田是绿洲灌区优化后作玉米产量性能指标及获得高产的可行栽培措施。     

少免耕与秸秆还田对极端土壤水分及冬小麦产量的影响

为了高效利用天然降雨,缓和农业水资源短缺,该试验在小麦、玉米一年两熟条件下,设置耕作措施和秸秆2个因素,其中耕作措施分为常规耕作、深松耕、耙耕、旋耕、免耕5种,秸秆因素分为玉米秸秆全量还田与不还田,共10个处理,研究了耕作措施与秸秆因素对极端土壤水分和冬小麦产量的效应。结果表明,无论秸秆还田与否,相对于常规耕作,深松耕能提高土壤水分充足期的土壤含水率,增加冬小麦产量,尤其是深松耕秸秆还田,比常规耕作无秸秆还田分别高25.74%和11.45%。秸秆因素在土壤水分充足时影响土壤含水率方面占主导地位,秸秆因素与耕作措施在土壤水分亏缺时影响土壤含水率和冬小麦产量方面均起着重要的作用。免耕、深松耕、耙耕与秸秆还田的交互效应能够增加集雨,提高冬小麦产量。研究结果还表明,冬小麦产量与土壤水分亏缺时土壤含水率相关不显著,而与土壤水分充足期土壤含水率相关显著。     

少免耕对小麦/玉米农田玉米还田秸秆腐解的影响

为了研究高产灌溉条件下土壤耕作模式对还田玉米秸秆腐解的影响,在山东龙口采用4种土壤耕作模式（常规耕作秸秆还田、旋耕秸秆还田、耙耕秸秆还田、免耕秸秆覆盖）进行了一年两季田间试验,测定了秸秆腐解率、秸秆腐解速率和秸秆的纤维素含量。结果表明：秸秆腐解速率与土壤温度具有显著的相关性。旋耕秸秆还田和耙耕秸秆还田两种少耕模式和常规耕作秸秆还田模式的秸秆腐解率、平均秸秆腐解速率无显著差异,说明少耕模式并不因减少耕作程序而降低作物秸秆在田间的腐解。免耕模式的秸秆腐解率和腐解速度显著低于以上3种耕作模式,经过小麦和玉米两个生长季节后仍有37.78%的玉米秸秆剩余,而且秸秆中纤维素质量分数为20.69%,腐解质量差,会对下年作物的出苗产生 影响。     

Biological soil properties in a long‐term tillage trial in Germany

After 37 years of different soil‐tillage treatments in a long‐term field experiment in Germany, a number of biological soil characteristics was measured. The field trial comprised six major treatments with different implements and various depths. In this paper, results from a comparison of long‐term use of a plow (to 25 cm depth), a chisel plow (to 15 cm depth), and no‐tillage are presented. The biological soil characteristics measured include the soil‐organic‐carbon (SOC) content, microbial biomass, enzyme activities, and the abundance and biomass of earthworms. Long‐term use of a chisel plow and no‐tillage increased the organic‐C content in the uppermost soil layer (0–10 cm) compared with the plow treatment. The microbial biomass and the enzyme activities arginine‐ammonification, β‐glucosidase, and catalase decreased with depth in all treatments. Arginine‐ammonification and catalase were higher in the plow treatment in soil layers 10 to 30 cm. Additionally, the chisel plow caused an increase in number and biomass of earthworms compared to both other tillage treatments. Differences in earthworm numbers and biomass between plowing and no‐tillage were not statistically significant.     

Effects of tillage on productivity of a winter wheat-vetch rotation under dryland Mediterranean conditions

An experiment was conducted to determine the effects of three tillage systems on crop yield in a winter wheat-vetch (Vicia sativa L.) rotation during 3-year growing seasons on a clay-loam soil in the northwest region of Turkey. The three tillage treatments were: (1) conventional tillage (CT); (2) shallow tillage (ST); (3) double disk tillage (DD).The wheat grain yield was significantly affected by tillage when averaged across years. The highest wheat grain yield was obtained with shallow tillage treatment. The year affected wheat grain yield significantly, mainly due to the distribution of rainfall through the growing season and probably due to the wheat-vetch rotation. Heads density and head length increased significantly with shallow tillage when compared with conventional tillage. Tillage practices had no significant influence on thousand kernel weight. Results from this study indicated that for a dryland wheat-vetch rotation cropping system, shallow tillage had higher wheat grain yields than that obtained from conventional tillage. Furthermore, mouldboard ploughing tillage in this crop rotation could be replaced by shallow tillage that would increase yield and would be likely to improve soil properties in the long-term. On the other hand, double disk tillage proved to be a promising soil management practice to improve vetch grain yield when compared with conventional tillage.     

Long-term energy use and economic evaluation of three tillage systems for cereal and legume production in central Spain

Three different experiments have been carried out in the area to the northeast of Madrid (central Spain) over 10 years with winter wheat (Triticum aestivum L.), winter barley (Hordeum vulgare L.), spring barley and vetch (Vicia sativa L.) grown for hay. In these experiments, three tillage systems were compared: conventional tillage (primary tillage was mouldboard ploughing to 300 mm depth), minimum tillage (primary tillage was spring tine cultivation either with a chisel or a cultivator to 150 mm depth) and zero tillage (direct drilling), in relation to energy consumption, production costs, energy efficiency and productivity, and economic returns. The experiments were performed on a Vertic Haploxeralf of a clay loam texture.The aforementioned variables were calculated considering every input (i.e. fertilisers, seeds, herbicides, machinery and fuel) including all the labour practices performed to harvesting. Post-harvesting activities were not included.The results showed that important energy and production cost savings may be achieved through minimum tillage and zero tillage, compared with conventional tillage. These energy savings ranged from 7 to 11% for cereal crops, whereas for vetch crops the reduction was 10% for minimum tillage and 15% for zero tillage. Production costs for minimum tillage were 13–24% less than for conventional tillage. For zero tillage these reductions ranged from 6 to 17%. For cereal crops, minimum tillage and zero tillage had energy productivities which were 18% and 20%, respectively, greater than that for conventional tillage. In most cases, yields of winter crops were similar, regardless of the tillage system considered. Only spring barley showed lower yields with zero tillage. For winter cereals the profitability with minimum tillage and zero tillage is higher than that with conventional tillage. However, spring barley is less profitable when using zero tillage.     

秸秆还田结合减氮调控旱地土壤硝化潜势维持作物产量的机理

  【目的】  氮肥过量使用所导致的氮素利用率低和环境污染等问题严重影响现代农业生产。研究秸秆还田改善旱地农田土壤性质、提升土壤肥力和氮素利用率的潜力和作用机理，为减少氮肥用量、提高作物氮素利用率和土壤肥力提供科学依据。  【方法】  本研究选取河南许昌潮土和云南曲靖红壤两种典型旱作农田，2016～2018年开展了田间玉米－大麦/小麦轮作定位试验，在两地同时设置以下4个处理:不施氮 (CK)、常规施氮 (N)、减氮20% (80%N)、减氮20%配合秸秆还田 (80%NS)，研究不同处理对土壤养分、土壤硝化潜势和作物产量及氮肥利用率的影响。  【结果】  与N处理相比，80%NS处理可稳定保持麦季抽穗期和玉米季抽雄期两种旱地土壤可溶性有机碳氮养分含量，促进土壤中NH₄+-N的积累并降低了NO₃–-N含量；80%NS处理使潮土和红壤硝化潜势分别降低了5.5%～33.9%和7.8%～37.5%；3年连续减施20%氮肥配合秸秆还田能够稳定产量并表现出一定的增产效果 (11.2%～20.4%)，提高氮肥利用率6.4%～10.3%；而80%N处理会使作物产量下降3.9%～13.4%，氮肥利用率降低1.8%～38.9%。  【结论】  连续3年减少常规氮施用量20%配合秸秆还田，不仅增加了土壤有机碳氮含量，还减缓了土壤的硝化作用，增加了土壤铵态氮积累，实现对作物所需养分的持续供应，因而在维持和提高作物产量的同时，提高了氮肥利用率。单纯降低氮肥用量则有降低作物产量的风险。     

保护性耕作条件下小麦田N2O排放及影响因素研究

采用静态箱—气相色谱法对保护性耕作和常规耕作小麦田的N_2O排放进行了原位测量,测量了土壤温度、水分、无机氮等相关影响因子。结果表明:(1)保护性耕作及常规耕作麦田N_2O的排放具有明显的季节性变化规律,各处理变化趋势较为一致。(2)N_2O的平均排放通量和季节排放量,除免耕秸秆还田外,保护性耕作与常规耕作差异显著。(3)在小麦生长季内,保护性耕作农田均表现为N_2O的排放源。(4)各处理N_2O季节排放量大小顺序为:耙耕秸秆还田(1.64 kg/hm~2)>旋耕秸秆还田(1.59 kg/hm~2)>常规耕作秸秆还田(1.48 kg/hm~2)>深松秸秆还田(1.42 kg/hm~2)>常规耕作无秸秆还田(1.34 kg/hm~2)>免耕秸秆还田(1.33 kg/hm~2),即,与常规耕作相比,保护性耕作(除免还)N_2O排放量增加。(5)温度是制约N_2O排放的关键因素,随着温度的升高N_2O表现出增加的趋势。(6)N_2O排放与水分、土壤无机氮含量无相关性。     

Weed seedbank response to tillage and crop rotation in a semi-arid environment

Seedbanks of five weed species were monitored in response to tillage and crop rotations in a semi-arid location in northern Jordan. Tillage practices of mouldboard- or chisel-plowing and cropping patterns of barley (Hordeum vulgare) planting or fallow were evaluated on permanently established subplots. Soil samples were collected from the upper 10 cm for three consecutive years, immediately after performing tillage and prior to planting. Soil seedbanks of the five dominant weed species (Anthemis palestina, Diplotaxis erucoides, Hordeum marinum, Rhagadiolus stellatus, and Trigonella caelesyriaca) were estimated by recovering viable seeds through greenhouse and laboratory procedures. At initiation, more viable seeds were present in soil subjected to mouldboard plowing than chisels plowing. In the following two sampling seasons, significant rotation by tillage interaction affected the seedbank of each species. Generally, mouldboard plowing increased weed seedbanks when combined with frequent fallowing. Conversely, chisel plowing combined with barley cropping generally reduced weed seedbank sizes. Results emphasized the importance of managing weeds during fallow to avoid the build up of H. marinum, a serious grass weed in semi-arid environments.     

旱作麦田保护性耕作蓄水保墒和增产增收效应

为了揭示渭北旱塬连作麦田不同保护性耕作措施下土壤蓄水保墒效果和冬小麦增产增收效应。于2007－2009年通过田间试验研究了渭北旱塬夏闲期免耕、深松和翻耕等3种耕作方式对麦田夏闲期蓄水保墒效果,以及3种耕作处理与平衡施肥、常规施肥和低肥等3种施肥处理组合对冬小麦生育期土壤水分动态、产量和经济效益的影响。免耕和深松较翻耕保墒作用好,夏闲期免耕、深松较翻耕0～300 cm土层3 a平均土壤含水率分别增加了0.6和0.5个百分点,平均贮水量分别增加了24.2和21.5 mm;生育期内平衡施肥免耕、深松较翻耕处理0～200 cm土层2 a平均土壤贮水量分别增加了17.7和14.4 mm;以平衡施肥深松处理产量最高,2 a平均产量高达5033.1 kg/hm2,较平衡施肥翻耕和平衡施肥免耕分别增产5.5%和6.3%;以平衡施肥免耕经济效益最高,2 a平均纯收益高达5 553.7元/hm2,较平衡施肥深松和平衡施肥翻耕分别增收3.3%和9.2%。综合考虑各处理土壤蓄水保墒效果和小麦增产增收效应,平衡施肥深松处理是渭北旱塬连作麦田较佳的耕作和施肥处理组合。     

Carbon dioxide emissions after application of tillage systems for a dark red latosol in southern Brazil

Soil tillage may influence CO₂ emissions in agricultural systems. Agricultural soils are managed in several ways in Brazil, ranging from no tillage to intensive land preparation. The objective of this study was to determine the effect of common soil tillage treatments (disk harrow, reversible disk plow, rotary tiller and chisel plow tillage systems) on the intermediate CO₂ emissions of a dark red latosol, located in southern Brazil. Different tillage systems produced significant differences in the CO₂ emissions, and the results indicate that the chisel plow produced the highest soil carbon loss during the 15 days period after tillage treatments were performed. Emissions to the atmosphere increased as much as 74 g CO₂ m⁻², at the end of a 2-week period, in the plot where the chisel plow treatment was applied, in comparison to the non-disturbed plot. The results indicate that the total increase on the intermediate term soil CO₂ emissions due to tillage treatments in southern Brazil is comparable to that reported for the more humid and cooler regions.     

Residue,tillage and N-fertilizer rate affected yield and N efficiency in irrigated spring wheat

Yield and nitrogen (N)-content in wheat was studied under applied treatments of crop residues (legume vs. cereal), tillage depths (deep vs. shallow) and N-fertilizer rates (0, 40, 80, 120 and 160 kg ha^?1) at wheat-maize cropping systems. Experiments were conducted at Agronomy Research farm, the University of Agriculture, Peshawar Pakistan, during winter season 2009–2010 and 2010–2011 crop growth seasons. Well-chopped crop residues (5 t ha^?1) on dry matter basis of legume (Vigna unguicuata) and cereal (Zea mays) were applied to soil and subsequently plowed with mold-board plow as deep tillage (DT) and cultivator as shallow tillage (ST) treatment (main plot treatments). A month after residue and tillage application, seedbed was prepared and wheat was planted with drill in rows 25 cm apart in middle of November each year. Phosphorus and potassium were applied uniformly 80 and 40 kg ha^?1, respectively during seedbed preparation. N-fertilizer rates were applied in two splits: half 15 days after sowing (DAS) and other half 45 DAS (sub-plot treatment). Uniform cultural practices were applied during crop growth and development. Legumes residues amendments showed better responses than cereal but lower than no-residue treatment for N-content in leaf blade before anthesis (LBA), after anthesis (LAA), straw N-content (SNC), grain N-content (GNC), grain N-uptake (GNU), crop N-removal (CNR), recovery efficiency of added nitrogen (REAN), N-use efficiency (NUE), grain N-uptake (GNU) and grain yield. Likewise, shallow tillage proved better than deep tillage system for LBA, LAA, SNC, GNC, GNU, CNR, REAN, NUE, GNU and grain yield. Increased N-fertilizer from control onwards showed significant (p > 0.05) increments in LBA, LAA, SNC, GNC, GNU, CNR, N-uptake and grain yield. Treatments interaction was also found significant (p > 0.05). Study suggested, regardless of the given treatments, GNU and grain yield were in strong positive linear relationship. Legume residue incorporated shallow out yielded GNU and NUE of spring wheat in wheat-maize cropping system. It is concluded that LR and ST with 120 kg N ha^?1 ensures production of good wheat quantity and quality.     

Carbon sequestration in a long-term conventional versus conservation tillage experiment

The impact of conservation tillage practices on carbon sequestration has been of great interest in recent years. Changes in the soil organic carbon (SOC) as influenced by tillage, is more noticeable under long-term rather than short-term tillage practices. This experiment analyzed the organic carbon status of soils sampled at depth increments from 0 to 60 cm after 25 years of five tillage treatments in a silt loam soil. Zero tillage (ZT) treatment was compared to conventional tillage practices of mouldboard and chisel plow operations conducted either during the fall or spring season in a randomized complete block design with four replications. The SOC was calculated on depth and equivalent soil mass bases. Contrast analysis showed a significantly (5%) higher soil bulk density for zero versus fall and zero versus chisel tillage operations at 5–10 cm soil depth. The SOC concentration was dependent on the depth of tillage operation and followed the trend of higher SOC for zero, chisel, and mouldboard tillage at 0–5, 5–10, and 20–40 cm depth, respectively. There were more significant differences in the SOC storage when expressed on depth compared to an equivalent soil mass basis. SOC storage was significantly higher for ZT at the 0–5 cm soil depth compared to conventional tillage practices. Contrast analysis on an equivalent mass basis showed that SOC storage was significantly higher for spring tillage compared to fall tillage at 0–60 cm depth. In conclusion, ZT practices increased SOC concentration and storage compared to conventional tillage operations only for the surface layer but not for the entire soil profile.