Nitrate leaching loss following application of organic manures to sandy soils in arable cropping.

Abstract. Experiments were set up at two sites to measure nitrogen (N) leaching loss from applications of separated pig/cattle slurry and cattle farmyard manure(FYM), during winters 1990/91–1993/94 (site A) and from broiler litter and FYM, during winters 1990/91–1992/93 (site B). The manures were applied at a target rate of 200 kg ha^-1 total N during the autumn and winter to overwinter fallow or top dressed onto winter rye. The total N in leachate was calculated from leachate N concentrations, in samples collected using ceramic cups buried at 90 cm, and an estimate of drainage volume. Nitrogen losses were greatest following manure applications in September, October and November but losses following applications in December or January were not significantly elevated above those from untreated controls. Losses were consistently lower from FYM than from broiler litter or separated slurry. The presence of a cover crop (winter rye) significantly reduced overall N leaching compared with the fallow, but only reduced the manure N leaching losses at one site during one winter when a high proportion of drainage occurred late. The incorporation of a nitrification inhibitor (DCD) with manures applied in October did not significantly reduce the manure N leaching.     

作物节水灌溉需水规律研究

基于节水灌溉条件下作物需水量试验资料,分析了控制灌溉和覆膜旱作节水灌溉的水稻需水规律以及节水高效灌溉模式下冬小麦、夏玉米和棉花作物的需水规律。结果表明,节水灌溉模式通过对水稻、冬小麦、夏玉米和棉花等作物产生的生长调控作用与补偿生长效应,使植株蒸腾量和棵间蒸发量较大幅度减少,各阶段需水量、需水强度和需水模系数均发生显著变化,形成了节水灌溉模式的主要农作物新的需水规律。可为节水灌溉制度的制定、节水型灌区动态配水及灌溉预报等提供科学依据。     

The effectiveness of cover crops during eight years of a UK sandland rotation

Abstract. Growing cover crops during the winter before spring-planted crops is often suggested as an effective method to decrease nitrate leaching. A four-course crop rotation (potatoes-cereal-sugarbeet-cereal) was followed through two rotations on a sandy soil in the English Midlands. Three management systems were imposed on the rotation to test their effects on nitrate loss. The effects of cover crops on nitrate leaching and crop yields were compared with the more conventional practice of over-winter bare fallow before potatoes and sugarbeet.
Cover crop N uptake was variable between years, averaging 25 kg ha⁻¹, which is typical of their performance on sandy soils in the UK. The cover crops usually decreased nitrate leaching but their effectiveness depended on good establishment before the start of drainage. Over 7 years, cover crops decreased the average N concentration in the drainage from 24 to 11 mg l⁻¹. Potato yield and tuber N offtake increased after cover crops. Ware tuber yield increased by an average of c . 8%; this was unlikely to be due to additional N mineralization from the cover crop because the potatoes received 220–250 kg fertilizer N ha⁻¹, and non-N effects are therefore implicated. Sugar yield was not increased following a cover crop.
After 8 years of nitrate-retentive practices, there were no measurable differences in soil organic matter. However, plots that had received only half of the N fertilizer each year contained, on average, 0.14% less organic matter at the end of the experiment.     

农田生态系统水分循环与作物水分关系研究

通过对我国不同类型农田生态系统水分循环与作物生产力关系的网络研究,探讨了我国主要类型地区小麦、玉米、大豆等几种主要作物的菡散耗水和需水规律、水分利用效率和作物水分生产函数,获得这些地区主要作物耗水需水特征及小麦水分生产函数。结果表明,在不同生态系统优化结构模式中作物与水分关系均得到极大改善,节约了作物用水,提高了作物产量和水分利用效率。     

Crop responses to applied soil compaction and to compaction repair treatments

Crop responses to annual compaction treatments (applied to whole plots) and management treatments to ameliorate compacted soil were determined in a field experiment on a Vertisol. Initially, all treatments except a control were compacted with a 10 Mg axle load on wet soil (26% gravimetric water content compared with a plastic limit of 22%). Annually applied axle loads of 10 and 6 Mg on wet soil (25–32% soil water) tended to reduce seedling emergence, grain yield (wheat, sorghum and maize), soil water storage and crop water use efficiency (WUE). Annual applications of an axle load of 6 Mg on dry soil (<22% soil water) had little effect on crop performance. Mean reductions in the yield of five crops (three wheat, one sorghum and one maize) in comparison with the uncompacted control were 23% or 0.79 Mg ha⁻¹ (10 Mg on wet soil), 13% or 0.44 Mg ha⁻¹ (6 Mg on wet soil) and 1% or 0.03 Mg ha⁻¹ (6 Mg on dry soil). Maize grown in the fifth year of treatment application was most affected by compaction of wet soil, its WUE being reduced from 14.3 to 9.7 kg ha⁻¹ mm⁻¹ in response to an axle load of 10 Mg. Reduced WUE was associated with delayed soil water extraction at depth. A 3-year pasture ley was the most successful amelioration treatment. A wheat and a maize crop grown after the ley outyielded the control by 0.33 and 0.90 Mg ha⁻¹, respectively. So the pasture not only ameliorated the initial compaction damage, with respect to crop performance, but resulted in improvements in two subsequent crops.     

低植酸作物的研究进展及展望

对植酸的含量与贮存形式及其生理功能、低植酸作物的营养功能、低植酸突变体作物的培育与研究、低植酸突变的分子遗传学特性及其可能机理进行了综述 ,并对今后的工作提出了展望。     

干旱状况下小区域灌溉冬小麦农田生态系统水热传输

该文采用涡度相关技术测定小区域灌溉冬小麦农田实际蒸散量和农田能量平衡各分量,分析表征农田地表获取能量再分配经典参数Priestly-Taylor系数（α=LE/LEeq）的变化特征。结果表明,在华北地区冬小麦返青至成熟期内,日变化过程中白天时间段内, Priestley-Taylor系数呈“U”型变化趋势,7︰00～18︰00 时刻内,α平均值为（1.324±0.334）,正午前后保持在1.05～1.17之间。 在冬小麦生育期季节变化过程中,Priestley-Taylor系数（α）平均值为（1.473±0.454）,远高于在湿润下垫面时（α＝1.26）的数值,在抽穗开花期内土壤水分充足时α最大值为2.317,拔节时期土壤水分胁迫时α值为0.410。干旱少雨状况下,进行小面积充分灌溉时,由于存在农田热平流现象将导致过多的蒸发蒸腾水分耗散,降低农田灌溉水的利用效率。     

转Bt基因作物毒素在土壤中降解特性的研究进展

总结了国内外转Bt基因作物在土壤中降解特性的研究结果,讨论了土壤有机、无机组分与毒素蛋白的关系,阐明了转基因毒素蛋白在土壤中的降解与影响因素,揭示了转Bt基因作物在土壤中降解的生态环境效应,并提出了今后应深入研究的问题和方向.     

葡萄利用结果枝副梢二次结果栽培试验

摘要：在桂林葡萄产区开展利用结果枝副梢促花二次结果的栽培试验,总结在新梢生长期喷多效唑（或矮壮素）、对新梢重度修剪促进冬芽提早萌发是整齐促放葡萄二茬果的关键技术,观测了二茬果果品品质和效益,提出了生产二茬果注意的技术问题。     

不同前茬作物与种植密度对大蒜农艺性状的影响

为研究不同前茬作物和种植密度对大蒜生长发育的影响,通过设定大豆茬(A1)、谷子茬(A2)和不同密度(M1、M2)两因素试验,测定不同处理的大蒜农艺性状指标和产量。试验结果表明,大蒜的农艺性状指标A1处理高于A2处理,M2处理高于M1处理,处理间产量没有显著差异。在生产中可以通过优化前茬作物和种植密度来提升大蒜商品性。