坡耕地等高反坡阶整地年限对土壤改良和玉米产量的影响

为探究等高反坡阶整地改良红壤坡耕地土壤质量的效果,利用田间定位试验,以滇中昆明松华坝迤者流域坡耕地试验区已实施等高反坡阶整地措施3(CRT 3),7(CRT 7),9(CRT 9)年的样地及原状坡耕地(CK)为研究对象,结合各样地玉米产量探明实施年限对土壤结构、肥力和酶活性特征的影响.结果 表明:等高反坡阶整地年限显著...     

晋陕峡谷河流阶地枣林土壤水分有效性及干燥化分析

选取晋陕峡谷河流阶地枣林土壤作为研究对象，采用土壤水分有效性指标A_w、土壤干燥化强度指数（SDI）等，定量研究河流阶地0~500 cm土层土壤水分有效性及干燥化的空间差异。结果表明：不同阶地土壤水分有效性A_w具有显著性差异（P<0.05），一级阶地（0.36）显著高于二级（0.08）和三级（0.14）阶地。不同深度土壤水分有效性差异为：0~200 cm土层土壤，除60~100 cm土层外，各层一级阶地显著高于二级、三级阶地（P<0.05）；110~300 cm、310~500 cm土层土壤水分有效性分别表现为一级阶地最低（最大值-0.06）和最高（最大值1.04）的水分状况(P<0.05)。对土壤水分有效性分级，一级阶地多处于无效水和富余水状态，二、三级阶地多处于难效水状态。200~500 cm土层土壤平均干燥化强度为：三级阶地（69.87%）>二级阶地（69.23%）>一级阶地（-24.78%）。综合考虑土壤水分相关指标及植被生长规律,河流三级阶地更适合枣树生长，而一级、二级阶地需加强灌溉管理，并增加适当的农艺措施才能满足枣树的正常生长发育条件。     

Quantifying soil displacement and tillage erosion rate by different tillage systems in dryland northwestern Iran

Redistribution of soil particles by the force applied by tillage is a major factor in soil degradation of agricultural land. Decreasing tillage intensity can reduce the amount of soil displaced and the distance moved and hence may reduce rates of erosion. To understand the relative importance of erosion, we tabulated machine, soil and landform properties likely to be involved. We compared soil displacement and tillage erosion rates under different systems, including mouldboard ploughing (conventional tillage), chisel ploughing (reduced tillage), stubble cultivator (minimum tillage) and no‐tillage under dryland agriculture in northwestern Iran. The area was undulating and so all tillage took place along contours. Metallic tracers were buried in the soil at known locations and depths and their recovery after tillage provided a measure of soil displacement and tillage erosion. Conventional tillage along a contour line caused significantly greater soil displacement (≃57 cm) in the direction of tillage than reduced and minimum tillage systems (~20 and ~15 cm, respectively). Conventional tillage also caused more lateral soil displacement (downwards in the main direction of slope, the tillage erosion rate) than reduced or minimum tillage systems (48 cm or 152 kg/m vs. 5 and 4 cm or 16 and 7 kg/m, respectively). Although a range of factors contribute to the tillage systems used by farmers, our results suggest that under dryland conditions, similar to those found in our study area, adoption of noninversion, reduced tillage along the contour, for example by chisel ploughing can substantially limit tillage erosion relative to conventional tillage.     

中国历史上的森林保护和农田开发

中国历史上在秦汉以前,森林资源的保护和利用处理得较好,有理论,有措施.汉以后对森林资源的保护即失控,甚至“罢山林之禁,与民共之”.农田开发是森林破坏的主要因素.唐宋以后,梯田遍及长江流域以南山区.明末清初甘薯、玉米引入中国后,更在边远山区掀起毁林垦荒高潮.毁林现象迄今未能制止.故必倾把人口、森林、农田、环境和生态纳入一个宏观的用养结合规划,建立新的“林-农”系统,才能扭转这一趋势.     

Trees,grasses, and weeds: species choices in farmed-developed contour hedgerows

Innovations intended to conserve soils and improve soil nutrient cycling have not been widely adopted because of technical problems and lack of fit with farmers' cricumstances. Research in Claveria, the Philippines, facilitated and monitored farmers' adaptation of contour hedgerows to fit their particular needs. Farmers tested different establishment methods and many hedgerow species. They initially planted a combination ofGliricidia sepium (a legume tree) andPennisetum purpureum. (grass). Later adoptors chose fodder grasses (especiallySetaria spp.) or naturally occuring vegetation in their hedgerows-either solely or in combination with other species, including weeds such asRottboellia cochinchinensis identified as crop problems. Upland rice and maize farmers who adopted contour hedgerows from 1987 through 1991 were interviewed in 1992. Although hedgerow-crop competition, grazing by neighbors' cattle, and added labor were problems, farmers viewed hedgerows as a way to reduce soil erosion and provide fodder. Farmers planting mulberry were disappointed after a silkworm project folded. Farmers now face the problem of soil nutrient depletion, leading to fallowing of fields with hedgerows and shifting to other parcels. A farmer decision tree model of the minimum necessary criteria for sustainable adoption of contour hedgerows is hypothesized.     

滴灌用水动活塞叠片式自动过滤装置的研制

以滴灌过滤装置自动化、节能和降低运行成本为目标,攻克了高效过滤、自动反冲洗和连续出水等关键技术难题,自主开发了水力驱动活塞反冲洗装置、螺旋盘、凹槽式叠片组合结构,成功研制了水动活塞叠片式过滤装置,并已批量生产和应用。试验结果表明,该装置具有自动过滤、清洗和排污功能,节能降耗效果显著,过滤洁净率大于95%,可替代进口产品。该装置的成功研制与推广应用对促进我国滴灌系统自动化和国产化具有重要意义。     

不同农艺措施组合对云南红壤坡耕地氮素平衡和流失的影响

通过对野外坡度为26．05％的径流小区实地观测，研究种植方式、施肥方式和等高植物篱条带3种农艺措施不同组合对云南红壤坡耕地氮素投入、带走平衡的影响。结果表明，在等高种植＋平衡施肥＋等高植物篱条带组合农艺措施条件下，收获玉米带走的氮为177．24kg·hm^-2，占水土流失和收获玉米带走氮总量的99．42％，水土流失带走1．03kg·hm^-2的氮，占水土流失和收获玉米带走氮总量的0．58％；顺坡种植＋农民习惯施肥收获玉米带走的氮仅为120.31kg·hm^-2，占水土流失和收获玉米带走氮总量的79．36％，而水土流失带走31．29kg·hm^-2的氮，占带走氮总量的20．64％。等高种植比顺坡种植增加收获玉米带走氮素13．36kg·hm^-2，减少水土流失带走氮素18．53kg·hm^-2；等高种植和平衡施肥条件下，等高植物篱条带因占用少量土地而减少收获玉米带走氮素6．09kg·hm^-2，减少水土流失带走氮素5．73kg·hm^-2；顺坡种植和习惯施肥条件下，等高植物篱条带减少收获玉米带走氮素5．39kg·hm^-2，减少水土流失带走氮素29．97kg·hm^-2；平衡施肥比习惯施肥增加收获玉米带走氮素49．66kg·hm^-2，减少水土流失带走氮素6．00kg·hm^-2。云南红壤坡耕地氮素的平衡主要与氮肥、钾肥施用量和玉米籽粒、秸秆产量有密切关系，施氮量高，氮素投入高于带走；平衡施肥玉米籽粒、秸秆产量高，氮带走总量较多，氮素带走略高于投入；习惯施肥玉米籽粒、秸秆产量低，氮素投入高，带走较少。     

Optimization of the contour ridge system for controlling nitrogen and phosphorus losses under seepage condition

Contour ridging can enhance the occurrence of deep seepage because more rainwater concentrates in the low areas along furrows when soil is saturated. Greater seepage could significantly increase nonpoint source pollution. To optimize the contour ridge system to effectively control nutrient losses under seepage condition, 23 treatments with three variables (row grade, field slope and ridge height) in five levels were arranged in a quadratic orthogonal rotation combination design. Results showed that field slope and interactions between the three factors did not significantly influence NO₃‐N and PO₄‐P losses. The dominant factor that controlled NO₃‐N loss was ridge height, followed by row grade. The smallest NO₃‐N loss was obtained at a ridge height of 8.72 cm and a row grade of 7.05°. The dominant factor that controlled PO₄‐P loss was ridge height. The optimal ridge height for efficiently controlling PO₄‐P loss was 9.79 cm. For simultaneously maximally controlling NO₃‐N and PO₄‐P losses, a ridge height of 9.26 cm, a row grade of 7.05° and a field slope of 5° were optimum. This study provides guidance for implementing the contour ridge system.