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1.
Soil organic carbon (SOC) and nitrogen (N) are directly influenced by tillage, residue return and N fertilization management practices. Soil samples for SOC and N analyses, obtained from a 23-year field experiment, provided an assessment of near-equilibrium SOC and N conditions. Crops included corn (Zea mays L.) and soybean [Glycine max L. (Merrill)]. Treatments of conventional and conservation tillage, residue stover (returned or harvested) and two N fertilization rates were imposed on a Waukegan silt loam (fine-silty over skeletal, mixed, superactive, mesic Typic Hapludoll) at Rosemount, MN. The surface (0–20 cm) soils with no-tillage (NT) had greater than 30% more SOC and N than moldboard plow (MB) and chisel plow (CH) tillage treatments. The trend was reversed at 20–25 cm soil depths, where significantly more SOC and N were found in MB treatments (26 and 1.5 Mg SOC and N ha−1, respectively) than with NT (13 and 1.2 Mg SOC and N ha−1, respectively), possibly due to residues buried by inversion. The summation of soil SOC over depth to 50 cm did not vary among tillage treatments; N by summation was higher in NT than MB treatments. Returned residue plots generally stored more SOC and N than in plots where residue was harvested. Nitrogen fertilization generally did not influence SOC or N at most soil depths. These results have significant implications on how specific management practices maximize SOC storage and minimize potential N losses. Our results further suggest different sampling protocols may lead to different and confusing conclusions regarding the impact of tillage systems on C sequestration.  相似文献   

2.
Tillage and residue management practices are sought in the subarctic where small grain production is often curtailed by the lack of soil water. Barley (Hordeum vulgare L.) grain yield and evapotranspiration were compared among four tillage and three residue management practices near Delta Junction, Alaska, USA from 1988 through 1991. Barley was hand-harvested in the fall whereas soil water content was determined biweekly during the growing season by neutron attenuation. Grain yield was similar for spring disk, fall chisel, and conventional (fall and spring disk) tillage across years. No tillage, however, resulted in a 260 kg ha−1 greater yield as compared with fall chisel and conventional tillage in 1990 when evaporative demand exceeded that in other years by nearly 10%. In 1990 and 1991, grain yield from plots devoid of stubble and loose straw was at least 200 kg ha−1 greater than from plots with stubble or stubble and loose straw. Barley consumed at least 15 mm more water to achieve the greater yield on no tillage or no stubble and loose straw plots. Water-use efficiency did not vary among tillage treatments, but was greatest in 1990 for plots devoid of stubble and loose straw. This study suggests that, in dry years with high evaporative demand, no tillage or removal of stubble and loose straw from the soil surface will enhance grain production and water-use efficiency of barley in the subarctic.  相似文献   

3.
Stand establishment and subsequent autumn development and growth are important determinants of winter wheat (Triticum aestivum L.) yield. Soil management practices change soil properties and conditions, which alter seedling emergence, crop development and growth. Pre-plant soil management practices were studied for 6 years in a wheat–fallow rotation in eastern Colorado, USA, to isolate the impacts of pre-plant tillage (PT) and residue level on winter wheat seedling emergence and autumn development and growth. A split plot design was used with PT, using a moldboard plow that incorporated surface residue, and with no-tillage (NT). The tillage systems represented the main plots and three residue levels within each tillage treatment as subplots: no residue (0R), normal residue (1R) and twice-normal residue (2R). Residue amount had little effect on emergence or autumn growth and development. PT resulted in soil water loss from the plow zone. NT plots had more favorable soil water levels in the seeding zone which resulted in faster, more uniform and greater seedling emergence in 4 out of the 6 years. This is especially critical for stand establishment in years with low rainfall after planting. Soil or air temperature did not account for differences among treatments. Earlier and greater seedling emergence in NT treatments resulted in greater autumn development and growth. Shoot biomass, tiller density and leaf numbers were greater in NT, and again residue amount had little effect. At spring green-up, NT treatments had greater soil water in the profile. Grain yield was always equal or greater in NT than in PT, and positively correlated with earlier/greater seedling emergence and autumn growth. NT will enhance soil protection and likely increase snow catch, reduce evaporation and benefit yield in semiarid eastern Colorado.  相似文献   

4.
Long-term field experiments are among the best means to predict soil management impacts on soil carbon storage. Soil organic carbon (SOC) and natural abundance 13C (δ13C) were sensitive to tillage, stover harvest, and nitrogen (N) management during 13 years of continuous corn (Zea mays L.), grown on a Haplic Chernozem soil in Minnesota. Contents of SOC in the 0–15 cm layer in the annually-tilled [moldboard (MB) and chisel (CH)] plots decreased slightly with years of corn after a low input mixture of alfalfa (Medicago sativum L.) and oat (Avena sativa L.) for pasture; stover harvest had no effect. Storage of SOC in no-till (NT) plots with stover harvested remained nearly unchanged at 55 Mg ha−1 with time, while that with stover returned increased about 14%. The measured δ13C increased steadily with years of corn cropping in all treatments; the NT with stover return had the highest increase. The N fertilization effects on SOC and δ13C were most evident when stover was returned to NT plots. In the 15–30 cm depth, SOC storage decreased and δ13C values increased with years of corn cropping under NT, especially when stover was harvested. There was no consistent temporal trend in SOC storage and δ13C values in the 15–30 cm depth when plots received annual MB or CH tillage. The amount of available corn residue that was retained in SOC storage was influenced by all three management factors. Corn-derived SOC in the 0–15 cm and the 15–30 cm layers of the NT system combined was largest with 200 kg N ha−1 and no stover harvest. The MB and CH tillage systems did not influence soil storage of corn-derived SOC in either the 0–15 or 15–30 cm layers. The corn-derived SOC as a fraction of SOC after 13 years fell into three ranges: 0.05 for the NT with stover harvested, 0.15 for the NT with no stover harvest, and 0.09–0.10 for treatments with annual tillage; N rate had no effect on this fraction. Corn-derived SOC expressed as a fraction of C returned was positively biased when C returned in the roots was estimated from recovery of root biomass. The half-life for decomposition of the original or relic SOC was longer when stover was returned, shortened when stover was harvested and N applied, and sharply lengthened when stover was not harvested and N was partially mixed with the stover. Separating SOC storage into relic and current crop sources has significantly improved our understanding of the main and interacting effects of tillage, crop residue, and N fertilization for managing SOC accumulation in soil.  相似文献   

5.
Soil tillage alters crop residue placement, soil moisture and soil physical properties, which in turn may affect soil chemical and microbial properties. The impact of tillage on microbial populations was investigated by studying soil microbiological, physical and chemical properties after 11 years of a tillage management experiment with continuous sorghum (Sorghum bicolor L. Moench) on an Orelia sandy clay loam (fine-loamy, mixed, hyperthermic Typic Ochraqualf). Soil from 0–7.5 and 7.5–15 cm depths was sampled from four replications of moldboard plow (MB), conventional till (CT), minimum till (MT) and no-till (NT) treatments in March (before planting) and May (during the growing season), 1989. Heterotrophic bacteria (HB) and actinomycete populations differed among tillage treatments before planting. Soil microbial populations differed with soil depth among all tillage treatments before the growing season (when no plants were present), but were similar among tillage treatments when counts by soil depth were composited, indicating that, although microbial distribution differed, total populations were similar. During the growing season, actinomycetes were lower in NT treatments, while HB counts were not significantly different between treatments. The similarity between treatments was attributed to drier soil conditions and the effect of plant roots in all treatments, which may have stimulated microbes similarly in all treatments. Ammonium oxidizers were lowest and dentrifiers highest in the NT soil a the 0–7.5 cm depth before planting. The sample obtained during the growing season indicated that soil nitrifier populations were usually greater in MT and NT treatments. The MB and CT treatments had significantly larger amounts of soil moisture, clay and nitrate than the NT and MT treatments, indicating that soil physical properties and nitrate levels were altered by tillage treatment. Soil nitrate was significantly correlated with nitrogen-transforming bacteria in several instances, although there was no predictable effect from soil depth or sampling date. In some instances, nitrifier counts fell and denitrifier counts increased as soil nitrate increased. HB and actinomycete population levels were not significantly correlated with the soil physical or chemical properties measured in this study. Although there were tillage treatment differences in soil physical (moisture, bulk density and clay content), chemical (nitrate-nitrogen, NO3---N) and microbiological properties (HB, actinomycetes, and denitrifier, nitrifier and ammonium oxidizer activity), generalizations about tillage system effects on soil microbiological properties were difficult to confirm because of the temporal nature of these differences.  相似文献   

6.
Conventional tillage creates soil physical conditions that may restrict earthworm movement and accelerate crop residue decomposition, thus reducing the food supply for earthworms. These negative impacts may be alleviated by retaining crop residues in agroecosystems. The objective of this study was to determine the effects of various tillage and crop residue management practices on earthworm populations in the field and earthworm growth under controlled conditions. Population assessments were conducted at two long-term (15+ years) experimental sites in Québec, Canada with three tillage systems: moldboard plow/disk harrow (CT), chisel plow or disk harrow (RT) and no tillage (NT), as well as two levels of crop residue inputs (high and low). Earthworm growth was assessed in intact soil cores from both sites. In the field, earthworm populations and biomass were greater with long-term NT than CT and RT practices, but not affected by crop residue management. Laboratory growth rates of Aporrectodea turgida (Eisen) in intact soil cores were affected by tillage and residue inputs, and were positively correlated with the soil organic C pool, suggesting that tillage and residue management practices that increase the soil organic C pool provide more organic substrates for earthworm growth. The highest earthworm growth rates were in soils from RT plots with high residue input, which differed from the response of earthworm populations to tillage and residue management treatments in the field. Our results suggest that tillage-induced disturbance probably has a greater impact than food availability on earthworm populations in cool, humid agroecosystems.  相似文献   

7.
A wide range of tillage systems have been used by producers in the Corn-Belt in the United States during the past decade due to their economic and environmental benefits. However, changes in soil organic carbon (SOC) and nitrogen (SON) and crop responses to these tillage systems are not well documented in a corn–soybean rotation. Two experiments were conducted to evaluate the effects of different tillage systems on SOC and SON, residue C and N inputs, and corn and soybean yields across Iowa. The first experiment consisted of no-tillage (NT) and chisel plow (CP) treatments, established in 1994 in Clarion–Nicollet–Webster (CNW), Galva–Primghar–Sac (GPS), Kenyon–Floyd–Clyde (KFC), Marshall (M), and Otley–Mahaska–Taintor (OMT) soil associations. The second experiment consisted of NT, strip-tillage (ST), CP, deep rip (DR), and moldboard plow (MP) treatments, established in 1998 in the CNW soil association. Both corn and soybean yields of NT were statistically comparable to those of CP treatment for each soil association in a corn–soybean rotation during the 7 years of tillage practices. The NT, ST, CP, and DR treatments produced similar corn and soybean yields as MP treatment in a corn–soybean rotation during the 3 years of tillage implementation of the second experiment. Significant increases in SOC of 17.3, 19.5, 6.1, and 19.3% with NT over CP treatment were observed at the top 15-cm soil depth in CNW, KFC, M, and OMT soil associations, respectively, except for the GPS soil association in a corn–soybean rotation at the end of 7 years. The NT and ST resulted in significant increases in SOC of 14.7 and 11.4%, respectively, compared with MP treatment after 3 years. Changes in SON due to tillage were similar to those observed with SOC in both experiments. The increases in SOC and SON in NT treatment were not attributed to the vertical stratification of organic C and N in the soil profile or annual C and N inputs from crop residue, but most likely due to the decrease in soil organic matter mineralization in wet and cold soil conditions. It was concluded that NT and ST are superior to CP and MP in increasing SOC and SON in the top 15 cm in the short-term. The adoption of NT or CP can be an effective strategy in increasing SOC and SON in the Corn-Belt soils without significant adverse impact on corn and soybean yields in a corn–soybean rotation.  相似文献   

8.
Crop management practices are needed that increase crop residue groundcover and reduce soil erosion after winter wheat (Triticum aestivum L.) planting in the Palouse region of northern Idaho and eastern Washington. Trials were conducted in 1997 and 1998 at the University of Idaho Kambitsch Research Farm near Genesee, Idaho, using farm scale equipment to evaluate dry pea (Pisum sativum L. subsp. sativum) and lentil (Lens culinaris Medik) residue production and groundcover across cultivars and tillage intensity. After harvest, legume plot areas were prepared for winter wheat seeding using four main plot tillage systems designed to give progressive levels of tillage intensity: no-till (NT), Ripper–Shooter™ (RS), RS plus one cultivation, and RS plus two cultivations. In 1997, the two dry pea cultivars produced significantly greater residue than the lentil cultivars. In 1998, ‘Pro 2100’ dry pea had significantly higher residue production than ‘Columbian’ pea and ‘Crimson’ lentil cultivars. In 1997, initial residue cover was highest with NT, averaging 74% groundcover across legume cultivars. After winter wheat seeding, residue cover declined for all tillage treatments, but was still highest at 40% residue cover under NT. In 1998, residue cover was lower for all tillage treatments across all cultivars than in 1997, but NT still had the highest initial residue cover. Wheat yield was not affected by tillage or previous crop treatments in either year. This study showed that NT and reduced tillage systems can maintain previous crop residue on the surface for soil conservation and subsequent crop yields.  相似文献   

9.
Conservation of soil water is an important management objective for crop production in the semi-arid tropics where droughts are persistent. Identification of the best tillage methods to achieve this objective is thus imperative. The integrated effects of conservation tillage on soil micro topography and soil moisture on a sandy loam soil were evaluated. The field experiment consisted of five tillage treatments, namely tied ridging (TR), no till (NT), disc plough (DP), strip catchment tillage (SCT) and hand hoe (HH). Data measured in the field included soil moisture content, surface roughness, infiltration and sorghum grain yield. A depth storage model was used to estimate depression storage TR treatment and the higher the surface roughness, the greater the depression storage volume. Regression analysis showed that random roughness decreased exponentially with increase in cumulative rainfall. Higher moisture contents were associated with treatments having higher depressional storage. Infiltration rate was significantly higher in the tilled soils than the untilled soils. The DP treatment had the highest cumulative infiltration while NT had the lowest. The Infiltration model which was fitted to the infiltration data gave good fit. Grain yield was highest in TR and least in NT, whereas DP and HH had similar yields.  相似文献   

10.
【目的】 探讨秸秆还田方式与施氮量对东北春玉米产量、干物质和氮素积累、转运的影响,明确适宜的秸秆还田方式及施氮量。 【方法】 连续两年在辽宁铁岭市进行了田间试验。设置秸秆还田方式 (旋耕、翻耕) 与施氮量两因素田间定位试验,研究了春玉米产量及干物质和氮素积累、转运特性。 【结果】 秸秆旋耕和翻耕还田产量和籽粒氮素积累量差异并不显著,但前者显著增加了地上部干物质和氮素积累量,及花后氮素积累量、花后干物质积累对籽粒干物质积累贡献率、花后氮素积累对籽粒氮素积累贡献率,而后者则显著提高了花前营养器官干物质、氮素转运量和转运率,花前营养器官干物质和氮素转运对籽粒干物质和氮素积累贡献率分别达到了12.4%、44.1%。随着施氮量的增加,产量和籽粒氮素积累量,地上部干物质和氮素积累量呈逐渐增大的趋势。但施氮量超过262.5 kg/hm2后,产量和籽粒氮素积累量差异则不显著。施氮量262.5 kg/hm2时,花前营养器官干物质和氮素转运量和转运率最高,花前营养器官干物质和氮素转运对籽粒干物质和氮素积累贡献率分别达到了16.7%、45.2%。 【结论】 短期秸秆旋耕和翻耕还田,春玉米产量和籽粒氮素积累量差异不显著,然而秸秆旋耕还田作业成本较低,且配施262.5 kg/hm2氮产量较高,可作为秸秆还田初期推荐施氮量。   相似文献   

11.
Dryland wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor (L.) Moench) are often grown using a wheat–sorghum-fallow (WSF) crop rotation on the semiarid North American Great Plains. Precipitation stored during fallow as soil water is crucial to the success of the WSF rotation. Stubble mulch-tillage (SM) and no-tillage (NT) residue management practices reduce evaporation, but the sparse residue cover produced by dryland crops, particularly sorghum, is insufficient to reduce soil crusting and runoff. Subsoil tillage practices, e.g., paratill (PT) or sweep (ST), fracture infiltration limiting soil layers and, when used with residue management practices, may increase soil-water storage and crop growth. Our objectives were to compare the effects of PT to 0.35 m or ST to 0.10 m treatments on soil cone penetration resistance, soil-water storage, and dryland crop yield with NT and SM residue management. Six contour-farmed level-terraced watersheds with a Pullman clay loam (US soil taxonomy: fine, mixed, superactive, thermic Torrertic Paleustoll; FAO: Kastanozems) at the USDA—Agricultural Research Service, Conservation and Production Research Laboratory, Bushland, TX, USA (35°11′N, 102°5′W) were cropped as pairs using a WSF rotation so that each phase of the sequence appeared each year. In 1988, residue management plots received PT or ST every 3 years during fallow after sorghum resulting in five treatments: (i) NT–PT, (ii) NT–NOPT, (iii) NT–ST, (iv) SM–PT, and (v) SM–NOPT. Cone penetration resistance was the greatest in NT plots and reduced with PT after 12, 23, and 31 months. Mean 1990–1995 soil-water storage during fallow after wheat was greater with NT than with SM, but unaffected by PT or ST. Dryland wheat and sorghum grain yields, total water use, and water use efficiency (WUE) were not consistently increased with NT, however, and unaffected by PT or ST tillage. We conclude, for a dryland WSF rotation, that: (1) NT increased mean soil-water storage during fallow after wheat compared to SM, and (2) ST and PT “subsoil” tillage of a Pullman did not increase water storage or yield. Therefore, NT residue management was more beneficial for dryland crop production than subsoil tillage.  相似文献   

12.
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.  相似文献   

13.
Field experiments were conducted for 6 years on a silty clay loam to study the effect of soil management on soil physical properties, root growth, nutrient uptake and yield of rainfed maize (Zea mays L.) and wheat (Triticum aestivum L.) grown in a sequence. Treatments were: no-tillage (NT), NT+pine needle mulch at a rate of 10 t ha−1 (NT+M), conventional tillage (CT), CT+pine needle mulch at a rate of 10 t ha−1 (CT+M) and deep tillage (DT). The soil is classified as a Typic Hapludalf and has compact sub-surface layers. The NT treatment increased the bulk density of the surface layer but this problem was not observed in the no-tilled treatment having mulch at the surface (NT+M). The CT+M and NT+M treatments favourably moderated the hydro-theregime resulting in greater root growth, nutrient uptake and grain yields of maize and wheat. The DT treatment, imposed only once, at the beginning of the study, also enhanced root growth and grain yields. The yields were similar to the mulched treatments for maize and somewhat less than the mulched treatments for wheat. Mulched treatments generally showed significantly greater total uptake of N, P and K than corresponding unmulched ones. Since NT+M was comparable to CT for maize and superior for wheat, the latter is preferable since it does not require ellaborate tillage.  相似文献   

14.
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。  相似文献   

15.
免耕覆盖有效提高夏玉米产量及水氮利用效率   总被引：3，自引：0，他引：3  
【目的】在旱区农业生产中,保护性耕作因具有保持水土、增产增收的优点而受到广泛关注,但其效应因地域环境、气候条件和栽培体系而异。本研究比较了半湿润易旱区旋耕垄作、免耕和免耕覆盖 3 种保护性耕作方式对夏玉米产量及水、氮利用效率的影响,为本地区筛选优化保护性耕作方式提供技术支撑。 【方法】试验于 2014 年和 2015 年 6～10 月份在陕西关中地区进行。采用裂区试验设计,主区为旋耕垄作 (RT)、免耕 (NT) 和免耕覆盖 (NTM) 3 种保护性耕作方式;副区为施氮 (N230) 和不施氮 (N0) 2 个施氮处理。 【结果】1) 与免耕和旋耕垄作相比,免耕覆盖处理可提高夏玉米耕层土壤生育期内含水量,降低高温季节耕层土壤温度,具有显著的增产效应,两年籽粒产量平均值的增幅分别为 13.2% 和 41.8%;2) 与旋耕垄作相比,免耕和免耕覆盖处理可显著降低夏玉米耗水量、增加地上部吸氮量,提高夏玉米的水、氮利用效率。其中,免耕和免耕覆盖的水分利用效率较旋耕垄作分别显著增加 7.1 和 10.3 kg/(hm2· mm),氮肥利用率分别增加 3.8 百分点和 10.1 百分点;3) 与不施氮相比,施氮能够促进夏玉米生长,提高地上部吸氮量、产量及水分利用效率,施氮各处理籽粒产量和水分利用效率的平均值较不施氮处理显著提高 49.5% 和 50.5%。 【结论】免耕和免耕覆盖尤其是免耕覆盖可有效调节土壤水热变化,解决本地区夏玉米生产中苗期干旱少雨导致的土壤水分匮乏问题,提高夏玉米籽粒产量及水氮利用效率。  相似文献   

16.
Little is known about the long-term effects of tillage and crop residue management on soil quality and organic matter conservation in subarctic regions. Therefore, we quantified wet aggregate stability, bulk density, pH, total organic C and N, inorganic N, microbial biomass C and N, microbial biomass C:N ratio, microbial quotient, and potential C and N mineralization for a tillage/crop residue management study in central Alaska. Soil from no-till (NT), disked once each spring (DO), and disked twice (DT, spring and fall) treatments was sampled to 20 cm depth in spring and fall of the 16th and 17th years of the study. Crop residues were either retained or removed after harvest each year. Reducing tillage intensity had greater impact on most soil properties than removing crop residues with the most notable effects in the top 10 cm. Bulk density was the only indicator that showed significant differences for the 10–20 cm depth, with values of 0.74 Mg m−3 in the surface 10 cm in NT compared to 0.86 in DT and 1.22 Mg m−3 in NT compared to 1.31 in DT for the 10–20 cm depth. Wet aggregate stability ranged from 10% in DT to 20% in NT. Use of NT or DO conserved soil organic matter more than DT. Compared to measurements made in the 3rd and 4th years of the study, the DT treatment lost almost 20% of the soil organic matter. Retaining crop residues on the soil conserved about 650 g m−2 greater C than removing all residues each year. Soil microbial biomass C and mineralizable C were highest in NT, but the microbial C quotient, which averaged only 0.9%, was not affected by tillage or crop residue treatment. Microbial biomass C:N ratio was 11.3 in DT and 14.4 in the NT, indicating an increasing predominance of fungi with decreasing tillage intensity. Barley grain yield, which averaged 1980 kg ha−1 over the entire 17 years of the study, was highest in DO and not significantly different between NT and DT, but weeds were a serious problem in NT. Reduced tillage can improve important soil quality indicators and conserve organic matter, but long-term NT may not be feasible in the subarctic because of weed problems and build up of surface organic matter.  相似文献   

17.
Limited information is available on the influence of high surface residue tillag systems and the interaction of weed control methods, cultivar maturity, and phosphorus fertilizer placement on yield parameters of dry bean (Phaseolus vulgaris L.) A 3-year field study was conducted on a Fargo clay (fine, frigid, montmorillonitic Vertic Haplaquoll) to evaluate the influence of surface or deep band placed phosphorus fertilizer, tillage systems (PLOW, SWEEP, STRIP, NOTILL) and weed control methods on harvest plant populations, seed yield and seed weight of ‘Upland’ (early maturity) and ‘C-20’ (late maturity) dry bean cultivars. Yield variables were influenced by cultivar planted and climatic conditions. Zinc deficient plants and decreased yield were observed with the ‘C-20’ cultivar when grown on PLOW system plots where phosphorus fertilizer was surface applied. Zinc deficient plants were not present when the phosphorus fertilizer was deep banded or none was applied. No zinc deficient plants were observed on NOTILL, STRIP and SWEEP system plots. Both cultivars matured 7 to 10 days earlier with NOTILL, STRIP and SWEEP systems when compared with the PLOW system. Dry bean yields were reduced 180 to 310 kg ha−1 by cultivation for weed control. Little difference in yields occurred among tillage systems when climatic conditions were normal. During a cool wet season, seed yields on PLOW system plots were 150 to 400 kg ha−1 higher than on plots of systems with surface residue. Seed weight, although lower on the late maturity cultivar, was not greatly changed by tillage or weed control method. Results from this study indicate that dry beans can be successfully grown with small grain surface residue systems in northern climatic areas where growing degree days exceed 1200 and growing season precipitation does not exceed 400 mm. Further, deep band placement of phosphorus fertilizer is essential in dry bean rotations to eliminate potential zinc deficiency on soils low in zinc. Switching to a high residue management system may require a special cultivator design to eliminate yield loss due to pruning of shallow roots present with high surface residue.  相似文献   

18.
In irrigated grain-growing soils on Canada's prairies, straw management can affect nitrogen (N) fertility and long-term soil organic matter reserves. We conducted a 2-year field experiment in southern Alberta, on a Dark Brown Chernozemic Lethbridge loam (Typic Boroll), to determine the effects of straw removal, tillage, and fertilizer timing on crop uptake of soil and fertilizer N. During the study (1991 and 1992), the crop was oat (Avena sativa L.) and wheat (Triticum aestivum L.), respectively, in an experiment that had been in a wheat-wheat-oat-wheat rotation since 1986. Five straw-tillage treatments were: straw-fall plow, straw-pring plow, no straw-fall plow, no straw-spring plow and no straw-direct seeding. Fertilizer N was applied in fall or spring. Ammonium nitrate (5 at.% 15N) was added at 100 kg N ha−1 in fall 1990 or spring 1991. For oat (1991), plant N derived from soil was higher under fall plow than under spring plow, higher with tillage than direct seeding, and unaffected by straw removal. The plant N derived from fertilizer was not affected by straw removal in fall plow treatments, but under spring plow, it was higher with straw removal. The plant N derived from fertilizer showed a significant straw-tillage × fertilizer timing interaction; with fall incorporated straw, plant N derived from fertilizer was 44.0 kg N ha−1 for spring-applied, and 30.6 kg N ha−1 for fall-applied N, but in other straw-tillage treatments there was no effect of fertilizer timing. Cumulative fertilizer N recovery (plant + soil) over the 2 years averaged 64.2%, and was unaffected by straw-tillage treatment. Fertilizer N recovery, however, was less with fall-applied N (61.3%) than spring applied N (66.8%). At mid-season, fall plow treatments had higher soil inorganic N and inorganic N derived from fertilizer than spring plow treatments, apparently because of less immobilization. The fall plow treatments also retained higher inorganic N after harvest. Straw removal and fertilizer timing did not influence soil inorganic N and soil inorganic N derived from fertilizer. N removal in straw (16 kg N ha−1 yr−1) could deplete soil N in the long-term. Long-term effects of tillage timing on soil N will depend on the relative amount of N lost by leaching with fall plowing and that lost by denitrification under spring plowing. With direct seeding, crop yield and uptake of soil N was less, and N losses by denitrification could be greater. Application of N in spring, rather than fall, should enhance crop N uptake, reducing N losses and enhancing long-term soil organic N.  相似文献   

19.
Soil organic matter (SOM) and phosphorus (P) fractions play a key role in sustaining the productivity of acid-savanna oxisols and are greatly influenced by tillage practices. In 1993, a long-term experiment on sustainable crop rotation and ley farming systems was initiated on a Colombian acid-savanna oxisol to test the effects of grain legumes, green manures, intercrops and leys as possible components that could increase the stability of systems involving annual cereal crops. Five agropastoral treatments (maize monoculture—MMO, maize–soybean rotation—MRT, maize–soybean green manure rotation—MGM, native savanna control—NSC and maize-agropastoral rotation—MAP) under two tillage systems (no till-NT and minimum tillage-MT) were investigated. The effects of NT and MT on SOM and P fractions as well as maize grain yield under the five agropastoral treatments were evaluated. Results showed that soil total C, N and P were generally better under no-till as compared to minimum-tilled soils. While P fractions were also generally higher under no-till treatments, SOM fractions did not show any specific trend. Seven years after establishment of the long-term ley farming experiment (5 years of conventional tillage followed by 2 years alternative tillage systems), MT resulted into moderately higher maize grain yields as compared to NT. The MGM rotation treatment had significantly higher values of maize yield under both tillage systems (4.2 Mg) compared to the NSC (2.3 Mg ha−1). Results from this study indicate that the rotational systems (maize–soybean green manure and maize-pastures) improved the soil conditions to implement the no-till or minimum tillage systems on Colombian savanna oxisol.  相似文献   

20.
The effects of five tillage treatments: no tillage (NT), disc harrowing (DH), mouldboard ploughing followed by disc harrowing (MPH), disc ploughing followed by disc harrowing (DPH), and disc ploughing followed by two passes of disc harrowing (DPHH) on crop residue cover, soil properties and some yield parameters of cowpea were investigated for a derived savannah ectone soil. The residue left on the soil surface for NT, DH, and MPH is not significantly different. The NT left 32.1 and 44.3% more residue on the soil surface than the DPH and DPHH treatments, respectively. The NT treatment had least average value of soil bulk density of 1.01 g/cm3. The mean soil bulk densities for the DH, MPH, DPH and DPHH vary between 1.20 and 1.35 g/cm3. The soil moisture content decreased with increasing soil depth. At the soil depth of 10–30 cm, the cone penetration resistance at NT was 1.18 MPa compared with 0.92 MPa for the DH treatment, although these were not significant (p≤0.05). The tillage treatments had a significant effect on grain yield, mass of leaves and stems, root length density, and number of pods per plant of cowpea except on the germination count. DH and NT treatments gave different grain yield and number of pods per plant but these values were not statistically different and represent the highest grain yield and number of pods per plant among the other treatments were considered. The root zone exploration revealed highest root density at shallow depths with the DH and MPH treatments.  相似文献   

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