平衡施肥及其对豫西旱地冬小麦水分利用率的影响

A study on balanced fertilization was conducted by means of long-term field experiments,and a conve-nient table for balanced fertilization was compiled.The experimental results about the effect of fertilization on water use efficiency of upland wheat showed that the input of inorganic fertilizer should be reduced in dry years.     

黄土高原沟壑区水平沟覆膜玉米种植试验及效益分析

黄土高原沟壑区水平沟覆膜玉米种植试验及效益分析党发宁（甘肃省正宁县水土保持工作站，７４５３００）黄土高原沟壑区是黄土高原地区的重要地貌类型之一，源、坡、沟、川台、梁峁为其基本地貌单元。区内气候温和，年降水量５５０～６５０ｍｍ，源西土壤侵蚀较轻，沟蚀严...     

小麦品种的抗旱性试验测定

在豫西邙岭旱区和豫西红土丘陵旱区，连续进行了４年小麦品种抗旱性筛选试验，选出了１０个抗旱性强、水分利用效率较高、耗水系数较低的小麦品种。并在豫西进行了大面积示范推广，取得了很好的效果     

Phosphorus requirements and nitrogen accumulation by N2-fixing and non-N2-fixing leguminous trees growing in low P soils

The variation in P uptake and use efficiency and N accumulation by Gliricidia sepium (N₂-fixing tree), Senna siamea and S. spectabilis (leguminous non-N₂-fixing trees) were examined in the field at Fashola (savanna zone), southwestern Nigeria, using four P rates, 0, 20, 40 and 80 kg P ha^-1. Growth of G. sepium and S. spectabilis responded to P application at 24 weeks after planting (WAP) and average yield increases of 58% and 145% were observed by the application of 40 kg P ha^-1 for the two species, respectively. Such a P response was not found in S. siamea at 24 WAP and for any of the species at 48 WAP. G. sepium accumulated more P (on average 162%) than S. siamea and S. spectabilis at 24 WAP and had greater root length and a higher percentage of mycorrhizal infection. However, at 48 WAP S. siamea had 2.5 times more P than G. sepium. Differences in the physiological P use efficiency (PPUE) between G. sepium and the non-N₂-fixing trees were significant at the 0 P level, being higher for S. siamea (average, 0.61 g shoot mg^-1 P) than for G. sepium (0.27 g shoot mg^-1 P). G. sepium had a consistently lower atom % ¹⁵N than S. spectabilis, while that of S. siamea for most of the time did not differ from that of G. sepium. The reference plant affected N₂ fixation extimates, with negative values and a higher variability (CV 60%) associated with S. siamea than with S. spectabilis (CV<20%). Consequently, S. spectabilis was selected as a better reference plant for measuring N₂ fixation in G. sepium. G. sepium fixed on average 35% and 54% of its N at 24 and 48 WAP, respectively. Except at the lowest P rate, percentage and amount of N fixed were not generally enhanced by P application.     

Economic land evaluation: why and how

Abstract. Economic land evaluation is a method for predicting the micro-economic value of implementing a given land-use system on a given land area. This is a more useful prediction of land performance than a purely physical evaluation, since many land-use decisions are made on the basis of economic value. Measures of economic suitability include the gross margin, net present value, internal rate of return, benefit:cost ratio, and utility functions based on these. The economic value of the in-situ resource quality of a land area may be inferred directly from land characteristics or from Land Qualities which, when less than optimum, result in decreased yields or increased costs. The economic value of geographic land characteristics may be determined by spatial analysis. Single or multi-criteria economic optimization and risk analysis can extend the economic land evaluation from a natural resource or management unit to a production or planning unit. Computerized tools may be used to assist in economic land evaluation.     

有机化工废弃物的土地处理研究

本文对三种供试工业废弃物，经土地处理后表明，发光细菌毒性明显降低，有的废渣处理物毒性已消除；Ａｍｅｓ试验和发光细菌自发暗变种的遗传毒减弱，由阳性下降为阴性，或阳性程度明显减弱。     

从15年变迁看西北黄土高原农业可持续发展之路--以延安市生态农业建设为例

以1981年、1985年分别对西北黄土高原农业生态系统考察的若干对比数据及其巨变，证实了生态农业建设是中国农业可持续发展的战略选择。分析了全国50个生态农业建设试点县（市）这一延安市七大生态工程原理与效益，说明了生态农业的可行性与可持续性，是适于我国国情、改善环境与农业生产同步发展的有效途径。     

小麦水分利用效率研究进展

介绍了小麦叶片冠层的水分利用效率估算模型,并阐述了小麦光合与水分利用效率关系的研究进展,为当前节水农业提供了大量信息。     

利用方式对红壤水稳定性团聚体形成的影响

本文研究了五种利用方式对红壤水性团聚体形成的影响。结果表明，＞稳定性团聚体含量：林地＞旱地＞荒地＞茶园＞果园。水稳定性团聚体数量以及团聚的水稳定性均与有机质的含量呈正相关。红壤开垦后，有机抽分解加快或补充减少是导致团聚体稳定性下降和水稳定稳定团聚体减少的主要原因。同理，恢复和改良红壤结构性及结构稳定性的关键是增加有机质的投入。     

Landsliding related to land-cover change: A diachronic analysis of hillslope instability distribution in the Sierra Norte,Puebla, Mexico

This study examines mass movement associated with land use change, particularly deforestation, from multiple perspectives. The significance of such understanding is related to the degree of impact landsliding may cause on human settlements and economic activities, and on forest ecosystems. In this paper, the distribution of hillslope instability in the Sierra Norte, Puebla, Mexico is addressed by means of a diachronic analysis, which involves the development of vegetation indexes, as well as vegetation fragmentation derived from Landsat-5 (TM) and Landsat-7 (ETM+) satellite images from 1989 and 1999, respectively. The time period was chosen to compare vegetation cover conditions prior and after the extreme October 1999 rainfall event that triggered hundreds of slope failures in the study area. Results suggested there was a significant vegetation reduction from 1989 to 1999, which was strongly expressed by an increase of 809 km² of bare surfaces. Additionally, areas with highest vegetation density (91–100%) decreased considerably, from 1245 to 363 km², resulting in a net vegetation reduction of 70%. Furthermore, it was possible to highlight that landslide concentration was much higher on surfaces that were bare and had low vegetation density (0–50%), representing 85% of hillslope instability, than on surfaces having a greater density of vegetation cover. Land use change and land degradation are precursors to environmental hazards, such as mass movement events, that pose serious threats to regional population distributions and economic vitality.