Interactive effect of tillage depth and mulch on soil temperature, productivity and water use pattern of rainfed barley (Hordium vulgare L.)

Soil porosity and organic matter content influence the hydrology, thermal status and productivity of agricultural soils. Shape, size and continuity of soil pores are determined by tillage practices. Thus appropriate tillage and mulch management can conserve residual soil moisture during the post rainy season. This can play a key role in enhancing productivity under the rainfed ecosystem of subhumid region in eastern India. A field study was carried out on a fine loamy soil from 1993–1994 to 1995–1996. Two tillage treatments were conventional ploughing (150 mm depth) and shallow ploughing (90 mm) depth. Each tillage practice was tested with three mulch management viz., no mulch, soil dust mulch and rice (Oryza sativa L.) straw mulch. Soil organic carbon, bulk density, moisture retentivity, soil temperature with productivity and water use pattern of barley (Hordium vulgare L.) were measured.Reduction in ploughing depth resulted in nominal increase in profile (0.0–1.2 m) moisture status, yield, and soil thermal status at 14:00 and water use efficiency (WUE). However, it decreased the magnitude of soil temperature in the morning (07:00). Straw mulch conserved 19–21 mm of moisture in the profile (1.2 m) over the unmulched condition. Both soil dust and rice straw mulching elevated soil thermal status at 07:00 as compared to unmulched condition, but this trend was reversed at 14:00. Straw mulching significantly increased grain yield and WUE over soil dust mulch and unmulched condition. Impact of straw mulch was more pronounced under shallow ploughing depth. Shallow tillage with rice straw mulching is recommended to the farmers to obtain higher level of yield and water use efficiency.     

Addition of Leucaena-KX2 mulch in a shaded coffee agroforestry system increases both stable and labile soil C fractions

Agroforestry systems have the potential to increase sequestration of atmospheric carbon dioxide (CO₂) as soil organic carbon (SOC) because of the increased rates of organic matter addition and retention. However, few studies have characterized the relative stability of sequestered SOC in soil. We characterized SOC storage in aggregate size and chemical stability classes to estimate the relative stability of SOC pools after the addition of Leucaena-KX2 pruning residues (mulch) from 2006 to 2008 in a shaded coffee agroforestry system in Hawaii. Soil samples were separated by microaggregate isolation, density flotation and dispersion, and acid hydrolysis, resulting in five distinct fractions that differed in relative stability: coarse particulate organic matter (POM), fine POM, microaggregate-protected POM, silt + clay hydrolyzable soil organic matter (SOM), and silt + clay non-hydrolyzable SOM. With mulch addition, the fine POM fraction increased. There was also a shift in the proportion of SOC to more stable silt + clay fractions. In the absence of mulch there was no significant change in SOC fractions. Given that the turnover time of SOC in silt + clay fractions is on the order of decades to centuries, the potential benefits of active shade management and mulching compensate for the loss of C sequestration in tree biomass from pollarding.     

Carbon sequestration and relationship between carbon addition and storage under rainfed soybean–wheat rotation in a sandy loam soil of the Indian Himalayas

Soil organic matter (SOM) contributes to the productivity and physical properties of soils. Although crop productivity is sustained mainly through the application of organic manure in the Indian Himalayas, no information is available on the effects of long-term manure addition along with mineral fertilizers on C sequestration and the contribution of total C input towards soil organic C (SOC) storage. We analyzed results of a long-term experiment, initiated in 1973 on a sandy loam soil under rainfed conditions to determine the influence of different combinations of NPK fertilizer and fertilizer + farmyard manure (FYM) at 10 Mg ha⁻¹ on SOC content and its changes in the 0–45 cm soil depth. Concentration of SOC increased 40 and 70% in the NPK + FYM-treated plots as compared to NPK (43.1 Mg C ha⁻¹) and unfertilized control plots (35.5 Mg C ha⁻¹), respectively. Average annual contribution of C input from soybean (Glycine max (L.) Merr.) was 29% and that from wheat (Triticum aestivum L. Emend. Flori and Paol) was 24% of the harvestable above-ground biomass yield. Annual gross C input and annual rate of total SOC enrichment were 4852 and 900 kg C ha⁻¹, respectively, for the plots under NPK + FYM. It was estimated that 19% of the gross C input contributed towards the increase in SOC content. C loss from native SOM during 30 years averaged 61 kg C ha⁻¹ yr⁻¹. The estimated quantity of biomass C required to maintain equilibrium SOM content was 321 kg ha⁻¹ yr⁻¹. The total annual C input by the soybean–wheat rotation in the plots under unfertilized control was 890 kg ha⁻¹ yr⁻¹. Thus, increase in SOC concentration under long-term (30 years) rainfed soybean–wheat cropping was due to the fact that annual C input by the system was higher than the required amount to maintaining equilibrium SOM content.     

Tephra-mulched soils irrigated with reclaimed urban wastewater in former dry-farming systems of Lanzarote (Spain)

On the island of Lanzarote, under extreme conditions of aridity and water scarcity, a certain amount of rainfed agriculture has been possible due to the use of tephra mulching, a system known locally as arenados, which is a very effective water and soil conservation system. The natural arenados are associated to already present tephra from recent volcanic eruptions. In artificial arenados a 5 to 20 cm layer of pyroclasts is placed over the soil. Over the last decade, the availability of urban reclaimed water (RW) has allowed irrigation networks to be established in artificial arenados with significant increases in crop yields. In this work, a preliminary evaluation of the sustainability of this new form of management was performed. Field plots irrigated with tertiary effluent for almost a decade were studied and compared with adjacent dry-farming fields, both cropped with sweet potatoes. In both cases, the soils had a covering of basaltic tephra mulch. The irrigation lines are placed on top of the mulch. Although this was not a controlled field experiment, since water and soil management was not exactly the same in the studied plots, some significant effects of RW irrigation on soil chemical properties were identified. Crop yields in the irrigated fields can be up to three times the yields obtained under rainfed conditions. The RW quality posed some restrictions for irrigation, particularly as regards salinity, sodicity and boron, although their buildup in soils appears to have been reduced by the mulch effect. In some field plots, crop critical threshold values of soil salinity and boron were reached with no harmful consequences. This developing soil degradation suggests that the sustainability of arenados systems under RW irrigation would appear to be under threat in the mid- to long-term based on current management practices. Further research is required on the salt and boron dynamics in this system, which is an example of conservation agriculture that also helps combat desertification.     

Improvement of rice (Oryza sativa L.) growth in upland conditions with deep tillage and mulch

The productivity of upland rice in Japan as well as in the world is low and unstable owing to scarce and unpredictable rainfall. The objective of this study was to examine whether agronomic methods could enhance grain yield of upland rice. Four field experiments were conducted from 2001 to 2003 in Nishitokyo, Japan, under upland conditions with different water supplies, in order to quantify the effects of deep tillage combined with deep placement of manure (50-cm depth), straw mulch (6 t ha⁻¹), or their combinations on the growth and grain yield of rice. Mulch kept surface soil moisture higher than without mulch even at reproductive stage, and it increased yield to the greatest extent under the most favourable conditions with much rainfall before heading (i.e., 2003). Deep tillage with deep placement of manure induced deep root proliferation and higher nitrogen uptake, increasing biomass production, and panicle number, and consequently grain yield was enhanced under the two lowest yielding environments with less rainfall before heading. Rice plants with deep tillage with deep manure application without mulch tended to have lower leaf water potential and higher diffusion resistance during drought, and negative effects on grain filling and harvest index in some experiments compared with the control. When deep tillage with deep placement of manure was combined with mulching in two experiments in 2002 and 2003, grain yield always enhanced compared with the control (P < 0.10, 6.0 t ha⁻¹ versus 5.4 t ha⁻¹ on average), suggesting their synergetic mechanisms for yield increase and stabilization. The results showed that deep tillage or mulching can improve grain yield of rice under drought-prone rainfed upland conditions in a temperate climate on an Andosol, and their combination had more consistent and greater positive effects.     

Straw mulching with fertilizer nitrogen: An approach for improving crop yield,soil nutrients and enzyme activities

Field experiments were conducted to study soil properties, soil enzymes activities, water use efficiency (WUE) and crop productivity after six years of soya bean straw mulching in the semi‐arid conditions of China. The experiment included four treatments: CK (Control), N (240 kg N ha^‐1), H (soya bean straw mulching at half rate 700 kg ha^‐1 with 240 kg N ha^‐1) and F (soya bean straw mulching at full rate 1,400 kg ha^‐1 with 240 kg N ha^‐1). Soil organic carbon (SOC), soil labile organic carbon (LOC), soil available N (AN), available P (AP) and enzyme activities were analysed after wheat harvesting in 2016 and 2017. Results show that straw amounts had positive effects on the soil fertility indices being higher for treatment F. The SOC, LOC, AN, AP and enzyme activities (i.e. saccharase, urease and alkaline phosphatase) were in the order of F > H > N > CK. High wheat grain yield and WUE were observed for F treatment. A total of six years mulching along with 240 kg ha^‐1 nitrogen fertilizer application is sufficient for wheat yield stability and improving soil properties except urease activities in the semi‐arid condition of China. However, the straw mulching amount should be further studied with minimum nitrogen fertilizer for an environment‐friendly and effective approach for improving the soil biological properties with adequate crop production on a sustainable basis in the semi‐arid region of China.     

Management influence on maize–wheat system performance,water productivity and soil biology

Cereal cropping productivity in the Indo‐Gangetic Plain (IGP) of India is declining, which may be overcome by diversification, alternate crop establishment methods and mulching. This study was conducted to determine whether no‐till flat (NTF), permanent raised beds (PRB) and nontraditional ex situ mulching would improve crop and water productivity, economic profitability and soil biological properties in an irrigated maize (Zea mays)–wheat (Triticum aestivum) system (MWS). NTF systems produced 10% higher economic net returns compared with PRBs. Non‐traditional mulching (Sesbania, Jatropha and Brassica) increased yields by >10% and net returns by >12% compared with no‐mulch. The water saving in PRBs compared with NTF systems was 79, 94 and 173 mm/ha in maize, wheat and MWS, respectively. PRBs saved 29.2% of irrigation water and improved the MWS irrigation water productivity (WP_I) by 24.5% over NTF. On average, mulching saved 23.8 mm/ha irrigation water over no‐mulch and improved WP_I by 12.0%. PRBs with ex situ mulching produced wheat and maize equivalent system yields lower than NTF but improved WP_I and soil biological properties. Jatropha and Sesbania mulching improved yield, water saving, WP_I and system profitability. In limited irrigation and no crop residue availability conditions, Sesbania, Jatropha and Brassica vegetation material have potential applications for ex situ mulching under PRBs for water saving and NTF for productivity.     

Effect of land use types on decomposition of 14C-labelled maize residue (Zea mays L.)

The effect of three land use types on decomposition of ¹⁴C-labelled maize (Zea mays L.) residues and soil organic matter were investigated under laboratory conditions. Samples of three Dystric Cambisols under plow tillage (PT), reduced tillage (RT) and grassland (GL) collected from the upper 5 cm of the soil profile were incubated for 159 days at 20 °C with or without ¹⁴C-labelled maize residue. After 7 days cumulative CO₂ production was highest in GL and lowest in PT, reflecting differences in soil organic C (SOC) concentration among the three land use types and indicating that mineralized C is a sensitive indicator of the effects of land use regime on SOC. ¹⁴CO₂ efflux from maize residue decomposition was higher in GL than in PT, possibly due to higher SOC and microbial biomass C (MBC) in GL than in PT. ¹⁴CO₂ efflux dynamics from RT soil were different from those of PT and GL. RT had the lowest ¹⁴CO₂ efflux from days 2 to 14 and the highest from days 28 to 159. The lowest MBC in RT explained the delayed decomposition of residues at the beginning. A double exponential model gave a good fit to the mineralization of SOC and residue-¹⁴C (R² > 0.99) and allowed estimation of decomposition rates as dependent on land use. Land use affected the decomposition of labile fractions of SOC and of maize residue, but had no effect on the decomposition of recalcitrant fractions. We conclude that land use affected the decomposition dynamics within the first 1.5 months mainly because of differences in soil microbial biomass but had low effect on cumulative decomposition of maize residues within 5 months.     

Organic carbon and stable C isotope in conservation agriculture and conventional systems

Conservation agriculture might have the potential to increase soil organic C content compared to conventional tillage based systems. The present study quantified soil organic carbon (SOC) and soil C derived from C₃ (wheat) and C₄ (maize) plant species using δ¹³C stable isotope. Soil with 16 y of continuous application of zero tillage (ZT) or conventional tillage (CT), monoculture (M) or rotation (R) of wheat and maize, and with (+r) and without retention (−r) in the field of crop residues were studied in the central highlands of Mexico. The highest SOC content was found in the 0-5 cm layer under ZTM and ZTR with residues retention. The soil cultivated with maize showed a higher SOC content in the 0-10 cm layer with residue retention than without residue. In the 10-20 cm layer, the highest SOC content was found in the CT treatment with residue retention. The SOC stock expressed as equivalent soil mass was greatest in the 0-20 cm layer of the ZTM (wheat and maize) and ZTR cultivated treatments with residue retention. After 16 y, the highest content of soil δ¹³C was found in ZTM + r and CTM + r treated soil cultivated with maize; −16.56‰ and −18.08‰ in the 0-5 cm layer, −18.41‰ and −18.02‰ in the 5-10 cm layer and −18.59‰ and −18.72‰ in the 10-20 cm layer respectively. All treatments had a higher percentages of C-C₃ (derived from wheat residues or the earlier forest) than C-C₄ (derived from maize residues). The highest percentages of C-C₄, was found in ZTM + r and CTM + r treated soil cultivated with maize, i.e. 33.0% and 13.0% in 0-5 cm layer, 9.1% and 14.3% in the 5-10 cm layer and 5.0% and 6.8% in 10-20 cm layer, respectively. The gross SOC turnover was lower in soil with residue retention than without residues. It was found that the ZT system with residue retention and rotation with wheat is a practice with a potential to retain organic carbon in soil.     

Soil structure and organic carbon relationships following 10 years of wheat straw management in no-till

Crop residue retention is important for sequestering soil organic carbon (SOC), controlling soil erosion, and improving soil quality. Magnitude of residue management impacts on soil structural properties and SOC sequestration is, however, site specific. This study assessed long-term (10 year) impacts of three levels (0, 8, and 16 Mg ha⁻¹ on a dry matter basis) of wheat (Triticum aestivum L.) straw applied annually on SOC concentration and physical properties of the bulk soil and individual 5- to 8-mm aggregates for the 0- to 50-cm soil depth under no-till (NT) on a Crosby silt loam (fine, mixed, active, mesic Aeric Epiaqualfs) in central Ohio. This study also quantified relationships between soil properties and straw-induced changes in SOC concentration. Changes in soil properties due to straw mulching were mostly confined to the upper 5 cm of the soil. Mulching increased SOC concentration, but it did not significantly change cone index (CI) and shear strength (SHEAR). Within the upper 0–5-cm soil depth, mulching decreased bulk density (ρ_b) by 40–50%, aggregate density (ρ_agg) by 30–40%, and particle density (ρ_s) by 10–15%, and increased tensile strength (TS) of aggregates by up to 14 times as compared to unmulched soil. At the same depth, soil with mulch retained >30% more water than soil without mulch from 0 to −1500 kPa potentials. The SOC amount was 16.0 Mg ha⁻¹ under no straw, 25.3 Mg ha⁻¹ under 8 Mg ha⁻¹ straw, and 33.5 Mg ha⁻¹ under 16 Mg ha⁻¹ straw in the 0- to 10-cm depth. Below 10 cm, differences in SOC pool between mulched and unmulched soil were not significant. Overall, SOC from 0- to 50-cm depth was 82.5 Mg ha⁻¹ for unmulched soil, 94.1 Mg ha⁻¹ for 8 Mg ha⁻¹ mulch, and 104.9 Mg ha⁻¹ for 16 Mg ha⁻¹. About 33% of C added with straw over the 10-year period was sequestered in soil. This means that 2/3 of the wheat straw applied was not converted to SOC and most probably was lost as emissions of CO₂ and CH₄. The annual rate of total C accrual was 1.2 Mg ha⁻¹ in soil mulched with 8 Mg ha⁻¹ and 2.2 Mg ha⁻¹ in soil mulched with 16 Mg ha⁻¹ of straw in the 0- to 50-cm depth. The percentage of macroaggregates (>5-mm) was six times higher under 8 Mg ha⁻¹ of straw and 12 times higher under 16 Mg ha⁻¹ compared to unmulched treatments. Macroaggregates contained greater SOC than microaggregates in mulched soil. The SOC concentration explained the variability in aggregate properties by as much as 96%. Overall, long-term straw mulching increased SOC concentration and improved near-surface aggregate properties.     

<Emphasis Type="Italic">Trichoderma</Emphasis> inoculation and trash management effects on soil microbial biomass,soil respiration,nutrient uptake and yield of ratoon sugarcane under subtropical conditions

A field experiment was conducted during 2003–2005 and 2004–2006 at the Indian Institute of Sugarcane Research, Lucknow, India to study the effect of Trichoderma viride inoculation in ratoon sugarcane with three trash management practices, i.e. trash mulching, trash burning and trash removal. Trichoderma inoculation with trash mulch increased soil organic carbon and phosphorus (P) content by 5.08 Mg ha⁻¹ and 11.7 kg ha⁻¹ over their initial contents of 15.75 Mg ha⁻¹ and 12.5 kg ha⁻¹, respectively. Soil compaction evaluated as bulk density in 0- to 15-cm soil layer, increased from 1.48 Mg m⁻³ at ratoon initiation (in April) to 1.53 Mg m⁻³ at harvest (in December) due to trash burning and from 1.42 Mg m⁻³ at ratoon initiation (in April) to 1.48 Mg m⁻³ at harvest (in December) due to trash mulching. The soil basal respiration was the highest during tillering phase and then decreased gradually, thereafter with the advancement of crop growth. On an average, at all the stages of crop growth, Trichoderma inoculation increased the soil basal respiration over no inoculation. Soil microbial biomass increased in all plots except in the plots of trash burning/removal without Trichoderma inoculation. The maximum increase (40 mg C kg⁻¹ soil) in soil microbial biomass C, however, was observed in the plots of trash mulch with Trichoderma inoculation treatment which also recorded the highest uptake of nutrient and cane yield. On an average, Trichoderma inoculation with trash mulch increased N, P and K uptake by 15.9, 4.68 and 23.6 kg ha⁻¹, respectively, over uninoculated condition. The cane yield was increased by 12.8 Mg ha⁻¹ with trash mulch + Trichoderma over trash removal without Trichoderma. Upon degradation, trash mulch served as a source of energy for enhanced multiplication of soil bacteria and fungi and provided suitable niche for plant–microbe interaction.     

Carbon input, loss and storage in sub-tropical Indian Inceptisol under multi-ratooning sugarcane

Changes in residue management and incorporation of organic manures may help in carbon sequestration, restoring soil organic carbon (SOC) and sustaining the productivity of land under a cropping system. An experiment of multi-ratooning sugarcane (Saccharum officinarum L.) was initiated in 2003 in Inceptisols of Indian subtropics, to assess the effect of different organic manures and chemical fertilizer, on the crop productivity and soil quality. The annual sugarcane shoot biomass production in organic manure treatments was at par with the chemically fertilized treatment. Gross input of carbon (GIC) by the sugarcane crop was estimated to be 11.7–12.4 t ha⁻¹ y⁻¹ in different organic manure treatments compared to 8.4 and 5.0 t ha⁻¹ y⁻¹ in NPK and control treatments, respectively. The respiratory loss of C (RLC) increased linearly with increasing input of C in soil and it ranged from 3.3 to 4.1 t ha⁻¹ y⁻¹ in different treatments with maximum in FYM and minimum in control treatment. The sugarcane biomass added in the soil humified at a rate constant of 0.38 in sub-tropical conditions and an addition of 3.9 t C ha⁻¹ y⁻¹ is required to maintain SOC in equilibrium. After 5 years of sugarcane cropping (one plant + four ratoons) an increase of 2.3–17.1 t ha⁻¹ in SOC over initial content was recorded with different treatments. Results in coming years from this long-term experiment shall add to the present calculated relationships between carbon addition and storage in sugarcane multi-ratooning crop production system under sub-tropical condition of India.     

Integrated Effects of Mulching Treatment and Nitrogen Fertilization on Cotton Performance under Dryland Agriculture

ABSTRACT

Crop production in arid regions is characterized with high temperature, drought and salinity which decrease water and nutrient use efficiency. This study was conducted to investigate the effect of wheat residue mulch in relation to N fertilizer application rates for cotton productivity under dryland condition of Uzbekistan. Main plots were control of no mulch addition and a 5 t ha^?1 mulch treatment. These plots were split into 5 N rate plots of 0, 70, 140, 210 or 280 kg of N ha^?1. The results showed that mulching pattern decreased soil temperature by 0.7–1.5°C as compared to conventional treatment (CT), regardless of N fertilization rates. The soil water storage increased by 41.8, 17.3, 48.0 mm in the flowering, boll formation and ripening stages of cotton, respectively under mulching treatment. Soil available N concentration and nutrients uptake by plants consistently increased with the increase of N fertilization rates with positive correlations. At flowering period, the plant height, chlorophyll content, stem diameter, and a number of fruit branches in plants were higher by 32.3%, 46.8%, 26.7% and 55.3%, respectively at 210 kg N ha^?1 under mulching treatment as compared to the non-fertilized control. The highest cotton yield was obtained at 210 kg N ha^?1 application under mulching treatment. The correlation difference between mulch and N application rates was higher (R² = 0.97) than the difference in CTs and N application rates (R² = 0.89). This study showed that mulching had a greater impact to preserve nutrients and water resources in the soil, thereby improved cotton growth and yield.     

麦秸覆盖条件下土壤蒸发阻力及蒸发模拟

模拟覆盖条件下的土壤蒸发对于农田水管理具有重要的作用。该文分析了留茬和秸秆覆盖模式下影响土面蒸发的因素,提出了留茬覆盖模式下蒸发阻力和土面蒸发模型,基于试验数据确定了公式中的参数。主要结果和结论:当表层2 cm土壤含水率高于0.23 cm3/cm3(约60%田持)时,土面相对蒸发量(土面蒸发量与20 cm蒸发皿蒸发量比值)基本保持稳定;当表层2 cm土壤含水率在0.05~0.23 cm3/cm3之间时,土面相对蒸发量随土壤含水率的降低而线性减小。覆盖会明显降低土壤蒸发,覆盖阻力随秸秆覆盖量增加呈指数增长。当表层2 cm土壤含水率在0.05~0.23 cm3/cm3之间时,土壤表面阻力随土壤体积含水率降低而线性增加。验证结果显示建立的土面蒸发模型及相应阻力参数能较好的模拟覆盖条件下的土面蒸发量。     

地膜覆盖对黄土高原旱作春玉米田土壤碳氮组分的影响

基于2年田间试验,研究了地膜覆盖对旱作春玉米田土壤有机碳、全氮及其组分的影响,试验包括地膜覆盖玉米田、无覆盖玉米田和裸地休闲3个处理,分层测定了0—40cm土层有机碳、全氮、颗粒有机碳氮、潜在矿化碳氮和微生物量碳氮含量。结果表明:在0—40cm土层,各处理间土壤有机碳和全氮含量均无显著差异。与不覆盖相比,地膜覆盖处理0—40cm土层颗粒有机碳氮及其所占比例分别降低了29.0%,33.3%,29.9%,35.7%;0—10cm土层潜在可矿化碳及其所占比例分别降低了17.8%和16.1%,潜在可矿化氮和微生物量碳及其所占比例无显著差异,但在0—10cm土层地膜覆盖微生物量氮含量及其所占比例分别较不覆盖处理提高了10.6%和10.5%(p0.05)。与裸地休闲相比,无覆盖处理0—40cm土层潜在可矿化碳氮分别提高了12.8%和14.7%,地膜覆盖处理则分别提高了7.8%和6.5%(p0.05),但种植玉米降低了微生物量碳氮含量及其所占比例。在0—40cm土层覆盖与否对潜在可矿化碳氮和微生物量碳氮影响不显著。总体来看,地膜覆盖能够在一定程度上提高表土微生物量氮组分及其所占比例,但显著降低了中活性碳氮组分含量及其比例,不利于长期的土壤碳氮固定。     

Effects of grass vegetation strips on soil conservation and crop yield under rainfed conditions in the Indian sub‐Himalayas

Vegetation strips (VS) along with conservation tillage, application of organic amendments and weed mulching improve crop yields by reducing run‐off and topsoil erosion. To investigate these issues, an experiment was conducted under rainfed conditions using grass VS for four and a half years (June 2007 to October 2011) at Dehradun, Uttarakhand, in the Indian Himalayan region. VS were incorporated in the experimental plots (Entisols) in a randomized complete block design in permanent 100 × 20 m (2000 m²) plots with a 2% slope to evaluate the effects of vegetation strips on run‐off, soil loss and crop yield. Three treatments were evaluated: (i) without VS with recommended NPK under conventional tillage, (ii) panicum as VS with recommended NPK under conventional tillage and (iii) palmarosa+ that consists of palmarosa as VS along with organic amendments (farmyard manure, vermicompost and poultry manure) and weed mulch under minimum tillage. The results show that soil loss and run‐off were significantly lower (P < 0.05) in plots under palmarosa+ than without VS treatment. Mean soil loss of 3.4, 5.2 and 7.1 t/ha was recorded from palmarosa+, panicum and without VS treated plots, respectively. Mean run‐off was 234, 356 and 428 mm from plots under palmarosa+, panicum and without VS, respectively. Maize yield was lower on the plots under palmarosa+ compared with panicum, but significantly higher (P < 0.05) than without a strip. The succeeding rainfed wheat yield was significantly greater in plots under palmarosa+ than in the initial years. The wheat yield equivalent was significantly higher in plots under palmarosa+ followed by panicum and without VS. Thus, vegetation strips are recommended for wider adoption to reduce run‐off and soil loss and to increase crop yield. The long‐term goal is to achieve a palmarosa+ system (palmarosa as a vegetation strip along with organic amendments, farmyard manure, vermicompost and poultry manure) and weed mulch under minimum tillage.     

旱地雨养农业覆膜体系及其土壤生态环境效应

覆膜技术作为一项有效提高粮食产量的重要手段,在中国西北地区雨养农业中得到广泛的推广应用。本文综述了地膜覆盖体系关于作物产量、土壤水分、土壤温度、土壤养分转化和迁移以及微生物数量和活性等方面的研究进展,以期为旱地雨养农业发展和完善覆膜技术体系提供理论支撑。研究表明:玉米、小麦和马铃薯覆膜处理增产显著,其平均增产率分别为26.2%、37.1%和29.8%;同时,增产受到覆膜方式影响,全覆膜处理增产效果最好,其玉米、小麦和马铃薯平均产量分别比半覆膜处理高30.0%、5.1%和26.4%。覆膜下玉米、小麦与马铃薯的水分利用效率分别比不覆膜处理高42.8%、10.9%和92.8%。覆膜处理影响硝酸盐在土体的空间分布,硝酸盐在膜下出现表聚现象;同时覆膜能够提高氮肥利用效率,减少氮素淋溶损失,降低氨挥发。但关于覆膜下反硝化过程的研究结论不一,还需进一步深入的探讨。覆膜对有机碳的影响与气候、土壤、作物、覆膜年限等有关,其研究结论尚有争议。另外,覆膜增加了农田土壤微生物量,改变土壤物理性状。尽管覆膜显著提高作物产量,其对生态环境却可能存在一定的影响,比如"奢侈耗水"现象,温室气体排放增加,土壤有机质耗竭,农膜残留等问题。因此,进一步系统研究覆膜对土壤生态环境的影响机理,完善覆膜技术体系与应用,全面评估覆膜体系的生态环境影响,对其在中国干旱地区农业生产的可持续发展具有重要意义。     

Impact of cultivation on soil organic carbon and carbon sequestration potential in semiarid regions of China

Dynamic changes in soil organic carbon (SOC) have become a popular topic in global research on organic carbon as part of the increasing attention being paid to food security and reducing greenhouse gas emissions. In this paper, the semiarid regions of China were selected as a research focus, and SOC data from 1980 to 2015 were analysed using IBM SPSS Statistics 20.0 software. SOC in farmland varied according to cultivated land type, mulching material type and planting method in the studied regions. The SOC content is 10.3–10.8 g kg⁻¹ in supplementally irrigated land and flat dry land, 7.1–8.7 g kg⁻¹ in terraced dry land and river beach land, and 6.2–6.4 g kg⁻¹ in sloping dry land. The SOC content increased to 16.1–17.4 g kg⁻¹ when crop stalks were used as mulch. The increase was only 11.5–13.5 g kg⁻¹ in soils mulched with film or sandstone. The SOC value in wheat, maize and potatoes sown on single or double ridges was 2.4%–3.2%, 35.7%–36.4% and 4.4%–4.8%, respectively, which are higher than the values for wheat, maize and potatoes sown using the flat planting method. The SOC sequestering potential also varied according to the previously noted factors and was improved from 224.1% to 383.8% depending on cultivated land type, from 96.5% to 182.3% depending on mulching material type and from 96.1% to 191.3% depending on planting method. The SOC sequestering potential can be improved by 453.2%–757.4% with the integration of the optimal cultivated land type, mulching material type and planting method. Thus, there is substantial soil carbon sequestration potential in China's semiarid regions.     

Effect of mulch and tillage system on soil porosity under wheat (Triticum aestivum)

Crop residues and reduced tillage become current tendency in modifying tillage due to better water management, organic and nutrient supply and increasing crop production. This study was carried out to quantify the effect of fodder radish mulching and different tillage systems in wheat production. In 2004–2006 the field trial was set up on Luvic Chernozems derived from loess. This experiment consisted of two factors: tillage system (conventional or reduced) and mulch (with or without). The air–water properties of soil with particular focus on macropore characteristics were investigated.The tillage system and mulch application significantly influenced physical properties of investigated soil. Reduced tillage, without mouldboard plough, increased the soil density with respect to conventional tillage. However, in the upper soil layer (0–10 cm) with mulch residues the bulk density decreased and reached the similar value as those obtained at conventional tillage (1.25 g cm⁻³). The macroporosity of soil with conventional tillage (14.79%) was significantly higher in comparison with reduced tillage (6.55%). The mulch of fodder radish added at reduced tillage increased the macroporosity in pore diameter range of 50–500 μm. These changes referred to all shape classes: regular, irregular and elongated pores. The lowest transmission pores content (0.078 cm³ cm⁻³) was noticed at the reduced tillage without mulch at the 0–10 cm layer. Due to lack of differences in storage pores the tillage and mulching had no effect on both AWC (available water content) and PWC (productive water content) values. The higher value of AWC was noticed in the upper soil layer (0.198 cm³ cm⁻³ in average), whereas in the 10–20 cm soil layer it was 0.186 cm³ cm⁻³. Similar relation was recorded in PWC values, 0.165 and 0.154 cm³ cm⁻³, respectively. The results obtained in physical properties of soil reflected in wheat yields. The yields obtained at reduced tillage system without mulch (5.54 t ha⁻¹) were significant lower with respect to treatment when mulch applied (6.79 t ha⁻¹). The mulch residues did not affect yields at conventional tillage (6.53 t ha⁻¹ without mulch and 7.00 t ha⁻¹ with mulch). The main conclusion is that the mulching can help to avoid yield reduction in wheat production when reduced tillage is used.     

柠条秸秆和地膜覆盖对土壤水分和玉米产量的影响

为了探讨北方农牧交错带不同保墒措施下旱地玉米的土壤水分特征及其对产量的影响,以甘农118为试验材料,监测了单膜(SFP)、双膜(DFP)、柠条秸秆沟埋(CPDP)和裸地(CK)4种不同处理下0~100 cm土壤水分季节变化、垂直变化及年际变化,测定了玉米产量和水分利用效率。结果表明:SFP和DFP处理明显改善0~40 cm土层土壤体积含水率,较CK处理保墒效果提高35.65%~47.91%,但随着玉米生育期的推进,由于玉米生长耗水和土壤蒸发作用,建植后土壤体积含水率均接近或低于萎蔫系数(7.20%)。连续2 a种植玉米4种处理土壤贮水量均有不同程度的减少,CPDP和CK处理土壤贮水量分别减少了68.42和68.07 mm,其次为SFP(53.49 mm),DFP减少最小(48.98 mm),说明研究区内玉米生长需要消耗大量土壤水分。SFP和DFP能够增加玉米对降雨和土壤水的利用,不同年份产量水分利用效率较CK处理分别提高12.55%~35.71%和25.11%~54.70%。SFP和DFP耗水量、产量和水分利用效率均无显著差异(P0.05),因此建议在研究区种植玉米时可以采取SFP措施,而CPDP耗水量较高、产量和水分利用效率相对较低,不宜采取此种保墒措施。