冀西北黄土丘陵沟壑区梯田地埂植物篱的固埂作用与效益分析

经对张家口地区梯田地埂植物篱的研究表明 ,其固埂作用非常显著 ,且能够改善土壤的理化性状及水分状况 ,有效地拦蓄地表径流及泥沙 ,提高作物产量 ,具有明显的经济效益 ,在当地具有很广泛的推广应用价值     

Influence of conservation tillage on winter bird use of arable fields in Hungary

Bird use of conservation tillage-established (CT—seedbed preparation without soil inversion) crops was assessed at two adjacent sites in western Hungary, in comparison with conventionally established (mouldboard ploughed—P) fields. Bird abundance was assessed in a typical rotation of spring-sown maize and winter wheat in three consecutive winters. In the first winter, several species and the guild of seed-eating passerines were significantly more abundant on CT established plots, in both crop types. In the second winter, only starlings were more abundant on CT plots. In the third winter, only skylarks favoured CT over P plots. In combination with agri-environment scheme measures designed to provide resources for biodiversity, conservation tillage could play a role in softening the impact of agriculture on farmland birds in Hungary and elsewhere in Eastern Europe, in addition to its potential for reducing soil erosion and diffuse pollution.     

陡坡地灌桑垄槽栽培研究

陡坡地灌桑垄槽栽培研究结果,免除土壤侵蚀的危害,其５０ｃｍ、１００ｃｍ土壤中,比对照区持水量高１０.２０％～３３.６７％、８.２７％～６５.３７％,含全氮率为对照的９０％,含全磷率高２.９％、２６.２％,含全钾率高３.１８％、８.０１％,而水解氮均为对照的６１.５％,速效磷高较对照３９.０２％、９７.７２％,速效钾为对照的９１.４８％、９２.５４％。公顷产桑叶量和蚕茧量均较对照高５～１０倍,经济效益较对照高１１.８８倍。     

MODELING SEDIMENT AND PHOSPHORUS LOSSES IN AN AGRICULTURAL WATERSHED TO MEET TMDLs1

ABSTRACT: This paper studies the effectiveness of alternative farm management strategies at improving water quality to meet Total Maximum Daily Loads (TMDLs) in agricultural watersheds. A spatial process model was calibrated using monthly flow, sediment, and phosphorus (P) losses (1994 to 1996) from Sand Creek watershed in south‐central Minnesota. Statistical evaluation of predicted and observed data gave r² coefficients of 0.75, 0.69, and 0.49 for flow (average 4.1 m³/s), sediment load (average 0.44 ton/ha), and phosphorus load (average 0.97 kg/ha), respectively. The calibrated model was used to evaluate the effects of conservation tillage, conversion of crop land to pasture, and changes in phosphorus fertilizer application rate on pollutant loads. TMDLs were developed for sediment and P losses based on existing water quality standards and guidelines. Observed annual sediment and P losses exceeded these TMDLs by 59 percent and 83 percent, respectively. A combination of increased conservation tillage, reduced application rates of phosphorus fertilizer, and conversion of crop land to pasture could reduce sediment and phosphorus loads by 23 percent and 20 percent of existing loads, respectively. These reductions are much less than needed to meet TMDLs, suggesting that control of sediment using buffer strips and control of point sources of phosphorus are needed for the remaining reductions.     

长期不同耕作方式对紫色水稻土重金属含量及有效性的影响

通过长期定位试验,研究了常规平作、水旱轮作、免耕冬水、垄作免耕和厢作免耕5种耕作方式对紫色水稻土剖面重金属(Fe、Mn、Cu、Zn、Pb、Cd)总量、有效量及水稻根、茎叶和糙米重金属含量的影响.结果表明,经过22 a的耕作,5种耕作方式对紫色水稻土剖面Fe、Cu、Zn、Pb、Cd总量的剖面分布状况影响不显著,而对土壤Mn的剖面分布状况影响显著,常规平作、水旱轮作及免耕冬水均导致表层土壤Mn向下层淋失.5种耕作方式下土壤Fe、Cu、Zn、Pb和Cd的有效量均随土层深度的增加呈降低趋势,而常规平作、免耕冬水、垄作免耕及厢作免耕土壤Mn有效量则表现出随土层深度的增加而增高的趋势.5种耕作方式下,表层土壤Fe、Mn有效量以水旱轮作最高,Zn、Pb有效量以常规平作最高,而Cu有效量受耕作方式的影响不显著.相关分析结果表明,表层土壤有效Fe与pH呈极显著的负相关关系,与有机质呈显著的负相关关系,有效Mn与pH和有机质均呈极显著的负相关关系,有效Zn与总Zn呈显著正相关关系.水旱轮作、垄作免耕及厢作免耕条件下水稻根部Fe、Mn含量,茎叶Fe、Mn、Cu、Cd含量,糙米Cu含量均高于常规平作和免耕冬水,水旱轮作能明显降低Cd向糙米的迁移系数,对降低糙米Cd含量有明显的效果,且水旱轮作条件下糙米Cd含量低于国家食品卫生标准.水稻根部Fe含量与pH呈极显著负相关关系,与有效Fe呈极显著正相关关系,根部Mn含量与pH呈极显著负相关关系,与有效Mn呈极显著正相关关系,茎叶中Mn含量与pH呈显著的负相关关系,与总Mn及有效Mn呈显著的正相关关系,茎叶和糙米Cu含量与pH均呈极显著的负相关关系,糙米中Zn含量与pH呈显著负相关关系,与CEC呈极显著正相关关系.结果表明,耕作方式主要通过影响土壤pH而影响土壤重金属的有效量及水稻重金属的含量,水旱轮作可提高表层土壤Fe、Mn活性,降低土壤Zn、Pb和Cd活性,并能在一定程度上降低糙米Pb、Cd含量,但也应注意长期的水旱轮作可能会导致表层土壤Mn过度向下层淋溶.     

短期保护性耕作措施对大豆-冬小麦轮作系统温室气体排放的影响

通过田间试验,在大豆和冬小麦生长季,进行常规翻耕(conventional tillage,T)、免耕(no-tillage with no straw cover,NT)、常规翻耕+秸秆(conventional tillage with straw cover,TS)、免耕+秸秆(no-till with straw cover,NTS)4种耕作措施处理,采用静态箱-气相色谱法测定土壤-作物系统CO_2和N_2O排放通量.结果表明:在大豆生长季,与T相比,NTS在开花-结荚期显著增加了CO_2累积排放量(P=0.045),增幅达27.9%;NT在鼓粒-成熟期显著降低了CO_2累积排放量(P=0.043),降幅达28.9%.与T相比,NT在鼓粒-成熟期的N_2O累积排放量降低了28.3%(P=0.042).在冬小麦生长季,与T相比,TS、NT在拔节-孕穗期使CO_2累积排放量降低了24.3%(P=0.032)和36.0%(P=0.041),在成熟期降低了26.8%(P=0.027)和33.1%(P=0.038).在返青期,NT、NTS、TS的N_2O累积排放量与T比较均没有明显差异,NTS比NT的N_2O累积排放量降低了42.0%(P=0.035).可见,保护性耕作措施对土壤-作物系统CO2排放的影响较大,对N2O排放的影响不明显.     

高台位旱地石灰性紫色土培肥研究

本文研究了高台位旱地石灰性紫色土的肥力退化因子,并针对紫色母岩矿质养分丰富、易风化成土的特点,以一种培肥耕作法-聚土免耕耕作法培肥土壤。结果表明,采用此耕作法的土壤具有防蚀、抗旱、培肥和自调能力,能提高系统生产力。     

SOIL EROSION AWARENESS AND USE OF CONSERVATION TILLAGE FOR WATER QUALITY CONTROL1

Water pollution through loss of topsoil from farmland continues to be a major problem, despite nearly 50 years of providing farmers technical and financial assistance for soil and water conservation. The technology for controlling erosion and water pollution is available, but farmers have been slow in implementing control practices. Past research has shown that farmers tend to be unaware of the seriousness of the erosion problem on their own operations. Using a random sample of farmers from central Iowa, the relationship is examined between awareness of a soil erosion problem and the use of conservation tillage. Results indicate that awareness of a soil erosion problem effects the use of conservation tillage, and that awareness can be enhanced by experiential educational strategies such as the development and implementation of a soil and water conservation plan.     

EFFECTS OF CROPPING SYSTEMS ON NO3-N LOSSES TO TILE DRAIN1

Abstract: Diverse cropping systems can have significant impacts on nutrient losses through tile drain systems and to surface water bodies (rivers and streams). Increased transport of nitrogen to water bodies can reduce dissolved oxygen and enrich the supply of nutrients, resulting in hypoxic zones. With the objective of reducing the transport of nutrients from agricultural watersheds, long term studies (1990 to 1998) were conducted in Iowa to investigate the impact of tillage, crop rotation, and N-management practices on NO₃-N leaching losses to tile drain water. Results of these studies indicated that continuous corn production systems required higher input of nitrogen fertilizers and resulted in significantly higher NO₃-N leaching losses compared to rotated corn in plots either fertilized with manure or urea ammonium nitrate. Also, rotated corn gave higher corn yields, 8 megagrams per hectare (Mg/ha) versus 6 Mg/ha, than continuous corn. The higher N application rates resulted in increased NO₃-N concentrations in tile water. A strip cropping system with alfalfa lowered NO₃-N concentrations in tile water to less than 10 mg/l. These studies indicated that better land use practices can reduce NO₃-N leaching losses to surface and ground water systems and will help in mitigating environmental concerns of the production agriculture.     

APPLICATION OF AN ENVIRONMENTAL AND ECONOMIC MODELING SYSTEM FOR WATERSHED ASSESSMENTS1

ABSTRACT: A National Pilot Project (NPP) on Livestock and the Environment was initiated in 1992 to help provide solutions to environmental problems associated with livestock production. A major development of the NPP was the Comprehensive Economic and Environmental Optimization Tool‐Livestock and Poultry (CEEOT‐LP), an integrated modeling system designed to produce economic and environmental indicators for alternative policy scenarios applied to intensive livestock production watersheds. The system consists of a farm‐level economic model (FEM) and two environmental models: the field‐scale APEX model and the watershed‐level SWAT model. To date, CEEOT‐LP has been applied to two watersheds in Texas and one in Iowa. Predicted reductions in P losses for two P‐based manure application rate scenarios, relative to baseline conditions, ranged from ?4 to ?54 percent across the three watersheds; however, N loss impacts ranged from a decrease of 34 percent to an increase of 79 percent. For five other alternative scenarios that were simulated for only one watershed, N and P loss impacts ranged between a reduction of 78 percent to an increase of 20 percent. Aggregate watershed‐level economic impacts of the seven scenarios spanned a spectrum of a 27 percent decrease to a 25 percent increase in profit, relative to the baseline.