Yield and yield components of maize and soil physical properties as affected by tillage practices and organic mulching

Maize (Zea mays L.) is an important grains cereal crop. Lots of farmers using tillage and mulching practices influence the final yield, to maintain up with the growing demand for food, fuel and feed. Field experiments were conducted to investigate the effects of tillage practices (i.e. conventional tillage CT, reduced tillage RT, deep tillage DT) and wheat straw mulching (i.e. no mulch and wheat straw mulch of 4, 8 and 12 Mg ha⁻¹, SM0, SM1, SM2 and SM3 respectively) on the growth, yield and yield components of maize and some of soil physical properties. The results showed that compared with RT, DT and CT decreased soil bulk density, as well as led to increase soil water content. Application of mulch treatments increased soil water content. DT and CT have been associated with greater plant height, yield components, grain and biomass yield than RT treatment. Plant height, yield components, grain and biomass yield as well as soil water content increased following mulching treatments. Mulching treatment of SM2 had the largest positive effects on maize yield. DT and CT that have potential to break the compacted zone in soil leading to a better soil environment and crop yield. The application of wheat straw mulch could be an efficient soil management practice for corn production in arid subtropical climate region.     

晚茬麦地膜覆盖栽培膜下CO2浓度的观测

二氧化碳是光合作用的原料。环境中CO_2供应是否充足,对作物的光合和产量有很大的影响。晚茬麦地膜覆盖栽培,改善了小麦赖以生存的环境条件,特别是膜下CO_2浓度的变化,对小麦的正常生长发育至关重要。因此,探讨覆膜麦膜下CO_2浓度的变化规律,对晚茬麦高产理论研究具有重要意义。     

黄土高原地膜春小麦地上干物质累积与转运规律

通过2个生长季的大田试验,研究了黄土高原半干旱地区地膜与露地春小麦地上干物质累积、转运规律.结果表明:与露地春小麦相比,地膜春小麦单株最大叶面积增加17.16%,最大绿叶面积峰值早出现6 d,开花前干物质积累量高8.97%;地膜春小麦叶片、茎秆、颖壳穗轴的输出率分别比露地春小麦高3.23%～3.67%、3.53%～4.55%和1.80%～3.63%;其转换率分别比露地春小麦高0.12%～0.46%、0.92%～1.90%和0.35%～0.87%;各非经济器官输出的干物质对籽粒干物质的贡献率比露地春小麦高1.9%～2.7%;地膜春小麦籽粒起始生长势、最大生长速率、活跃生长期均高于露地春小麦;而达最大生长速率的天数短于露地小麦;地膜春小麦籽粒灌浆期具有较强的生长势,灌浆速率快,灌浆时间长,最终表现为粒重高、产量增加36%.     

Antioxidative defenses and water deficit-induced oxidative damage in rice (Oryza sativa L.) growing on non-flooded paddy soils with ground mulching

Rice (Oryza sativa L.) cultivation under non-flooded conditions using polyethylene film as ground mulching materials, namely plastic film-mulching cultivation system (PFMCS), is an alternative to the conventional rice cultivation system in regions where rainfall and fresh water resources are limited. Two-year field trials (1998–1999) were performed in this study to investigate the growth-stage-dependent changes in activities of antioxidative enzymes and lipid peroxidation in leaves of rice subjected to mulching with plastic film or kraft paper and zero mulching under non-flooded conditions compared with continuously flooded treatment. Significantly higher activities of peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) but lower concentration of malondialdehyde (MDA) were observed in mulching treatments than in zero mulching treatment at all growth stages in the drier growing season (1999). The concentration of MDA was significantly higher especially at late growth stages in zero mulching treatment than in the other treatments. In contrast, essentially no significant difference existed in the activities of the major antioxidant enzymes (except POD) or in the concentration of MDA between any two treatments in the wetter growing season (1998). This change tendency of antioxidant enzyme activity and MDA level over two contrasting growing seasons was in line with both soil and leaf moisture status, and rice yields of different treatments. These results strongly suggest that plastic film-mulching treatment or paper mulching treatment significantly alleviated oxidative damages induced by water-deficit stress in rice. The efficacy of ground-mulching-induced enhancement of antioxidative defense to drought stress is discussed with respect to water deficit status in both soils and rice plants.     

Copper mobility and toxicity of soil percolation water to bacteria in a metal polluted forest soil

In order to assess the success of in situ remediation of coniferous forest soil polluted by a Cu–Ni smelter, the total Cu concentration in soil percolation water, the fluxes of Cu down through the soil profile, and the toxicity of soil percolation water to soil bacteria were studied. Total Cu in percolation water was also fractionated into free ionic and complexed forms. The toxicity of the percolation water was measured by the [³H]-thymidine incorporation method, which measures bacterial growth rates. Soil percolation water was collected during one growing season by zero tension lysimeters inserted at depths of 0.2 and 0.4 m in the soil. The treatments consisted of a control, mulch application to the forest floor (M) and mulch application after removing the polluted organic soil layer (MR). The mulch consisted of a mixture of compost and woodchips (1/1; vol/vol). Analysis of Cu species and dissolved organic carbon (DOC) indicated that DOC leached from the mulch and complexed Cu into forms that were less toxic to soil bacteria. At 0.2 m depth percolation water toxicity was 19% lower in the M and 42% lower in the MR treatment than in the control. Toxicity correlated with the Cu²⁺ concentration, which was 61 and 84% lower in the M and MR treatments, respectively, compared to the control. However, there were signs that total Cu had leached down through the soil profile, the leaching being more pronounced in the MR treatment.     

陕北半干旱区沟垄覆膜集水模式下糜子边际效应及生理特性

通过连续3年大田定位试验,研究了陕北半干旱区不同沟垄覆膜集水模式下糜子边际效应和生理特性.试验设4种不同的沟垄宽度(带型),垄∶沟分别为40 cm∶40 cm(P₄₀)、60 cm∶60 cm(P₆₀)、80 cm∶80 cm(P₈₀)、100 cm∶100 cm(P₁₀₀),对照为露地平播(NM).结果表明: 随着沟垄宽度的增大,糜子的产量边际效应指数和边际效应增大,边行的增产作用呈上升趋势,最大增产率达207.7%,而中行的增产作用呈下降趋势,增产幅度最低仅为103%.带型60 cm∶60 cm的糜子产量在3年中均为最高.同一处理内,边行对糜子产量的贡献率大于中行,差异达到显著水平.不同带型边行的叶绿素含量、Chl a/Chl b、光合速率均大于中行;沟垄宽度越大,边行的光合能力越强,中行的光合能力越弱.带型60 cm∶60 cm是陕北半干旱区糜子种植的适宜带型.     

农业活动及转基因作物对农田生物多样性的影响

农田生物多样性是生态系统生物多样性的重要组成部分,但较少受到关注.近50年来,由于农业活动引起的环境污染、生境破碎和单一化种植等严重威胁着农田生物多样性.为了了解各因素对农田生物多样性的影响程度,优化农田管理措施,以提高农作物产量并降低环境影响,本文综述了种植方式、地膜覆盖、农药和化肥使用等农业活动及转基因作物对我国农田生物多样性的影响.农药和化肥的过度使用对农田生物多样性的影响最大;而转基因作物对农田生物多样性的影响受诸多因素影响,如携带的转基因性状等.需要加强转基因作物生态环境影响评价研究,特别是对农田生物多样性的潜在影响.农业生产活动应当与农田生物多样性保护密切结合,不仅有利于提高农作物产量,同时也可减少对环境的负面影响.     

不同有机物覆盖对冷凉地区苹果园土壤水温环境及速效养分的影响

为了探究不同有机物覆盖对冷凉地区果园土壤理化性质的影响,在‘寒富’苹果园设置了杂草、稻草、玉米秸秆、粉碎枝条4个覆盖处理,对比分析了各处理果园土壤水分、养分等指标的变化.结果表明: 有机物覆盖增加了土壤含水量,以干旱季节最为明显;减缓了春季土壤温度上升速度,不利于果树前期生长,但降低了夏季土壤的最高温,提高了秋冬季土壤的最低温;提高了土壤的pH值,以玉米秸秆覆盖处理最为明显,减轻了土壤酸化,使土壤pH接近中性;不同程度提高了土壤有机质含量,以杂草覆盖处理最为明显.覆盖还增加了土壤碱解氮、速效磷、速效钾含量,但稻草覆盖处理碱解氮含量低于对照.     

秸秆覆盖和灌溉对冬小麦农田光能利用率的影响

研究了秸秆覆盖和灌溉对冬小麦农田光能利用率的影响.结果表明,秸秆覆盖降低了冬小麦的基本苗、分蘖数及生育前期的叶面积指数,但到生育后期,覆盖处理的叶面积指数反而升高.覆盖和灌溉降低了光合有效辐射（PAR）的底层透射率和冠层反射率,使PAR总截获率升高.覆盖和灌溉主要增加了40～60 cm高度的PAR截获率.覆盖处理籽粒光能利用率降低,茎叶光能利用率和总光能利用率升高.