Summary Some intensive agricultural practices result in soil degradation through loss of soil organic matter. Organic farming may mitigate this problem, if managed properly, but may result in a yield penalty compared with conventional systems. Biochar addition to soil could influence both agricultural systems, but previous studies are not definitive about its impact on soil processes. Sandy soils are more susceptible to the effects of reduced soil organic matter on soil hydrology and nutrient dynamics. Nitrogen (N) is important for crop growth and soil water content can influence its transformation and cycling. This study explored the effect of biochar amendment on soil water retention and nitrification processes in soils under organic and conventional management. Carbon dioxide evolution was used as an indicator of related microbial activity. A water release curve study and a 60‐day incubation experiment were set up to consider the effect of biochar application on organically and conventionally managed sandy loam soils. The results showed that addition of biochar increased water retention for both soils and this is attributed to its porous structure. On incubation of an organically managed soil, with green‐waste compost, initial ammonium level was small, reflecting microbial demand for N. The large cation exchange capacity of the organically managed soil retained ammonium, reducing availability for nitrification. Carbon dioxide evolution increased with continuing small contents of ammonium and nitrate when biochar was added to the organically managed soil. Biochar enhanced nitrification without increased respiration during incubation of a conventionally managed soil with added mineral N; a possible explanation for this enhancement is the increase in pH resulting from the biochar addition.

The rapid development of industry and urban areas, population growth and rising living standards have all resulted in an increased water demand for non-agricultural uses in the North China Plain, therefore decreasing the water availability for irrigation. Technologies that favour a reduced demand and water-saving practices in irrigation are required to assure the sustainability of water use in agricultural production. This paper presents main research results relative to the integration of water and soil management technologies which may contribute to improving the use of water and land in agricultural production, reducing demand for irrigation, and more efficient use of groundwater. Improved estimates of crop irrigation requirements, better irrigation scheduling for the winter wheat crop and improved surface irrigation systems, result in water saving corresponding to about 100 mm in very dry years and up to 250 mm in average years with a small yield increase. These savings represent 16-33% of water use during the wheat crop season. Improvements in soil management lead to improved soil fertility and physical properties (including hydraulic conductivity). These improvements produce potential increases in summer maize yields of between 10 and 20%. Copyright # 2003 John Wiley & Sons, Ltd.key words: evapotranspiration; crop irrigation requirements; irrigation scheduling; basin irrigation; tillage; soil amendments; reduced demand; wheat; maize RÉ SUMÉ Dans la Plaine du Nord de la Chine, le développement rapide de l'industrie et des zones urbaines, la croissance de la population et l'amélioration de leur niveau de vie ont donné lieu à une demande en eau pour des usages non agricoles toujours accrue, ce qui a fortement diminué sa disponibilité pour l'irrigation. Des technologies qui favorisent la réduction de la demande agricole et l'économie d'eau en irrigation sont donc requises pour assurer la durabilité de l'utilisation de l'eau en irrigation. Cet article présente des résultats de recherche relatifs à la gestion de l'eau et du sol à l'échelle de la parcelle qui peuvent contribuer à améliorer l'utilisation de l'eau et de la terre, la réduction de la demande et l'utilisation plus efficiente des eaux souterraines. En irrigation, les solutions proposées concernent l'estimation plus rigoureuse des besoins en eau des cultures irriguées, l'amélioration de la conduite des arrosages et la modernisation des systèmes d'irrigation de surface, ce qui peut conduire à réduire la demande de 100 mm pour les années de sécheresse et jusqu'à 250 mm pour l'année moyenne. Ces réductions représentent à peu près 16 à 33% de l'eau utilisée pour l'irrigation du blé, la principale culture irriguée dans la région. D'autre part, l'amélioration des pratiques de gestion du sol peut conduire à des effets positifs sur les proprietés hydrauliques et la fertilité du sol, ce qui pourrait conduire à augmenter la productivité du maïs en pluvial de 10 à 20% dû tant à une meilleure utilisation des pluies d'été qu'à des conditions de sol plus propi...

Soil erosion is potentially a problem on most land restoration projects on steep slopes. By removing the topsoil, washing out seeds and young plants, and cutting rills and gullies into the landscape, erosion can hinder revegetation and either delay or prevent the establishment of the vegetation cover which will provide the long-term protection of the slope. Even moderate erosion can scar the landscape and delay or prevent the growth of vegetation, thereby hindering restoration work. Uncontrolled erosion can result in environmental damage downslope where sediment can bury farmland, cover roads and settlements in silt, and pollute water bodies, with detrimental effects on fish and other aquatic life. Along pipeline rights-of-way, there is the additional hazard that, if unchecked, erosion can lead to the removal of backfill to depths of several metres and to exposure of the buried pipe. The control of erosion during and immediately after pipeline construction is important in order to prevent the exposure of shallow-laid pipes, avoid liabilities for environmental damage and promote the rapid establishment of vegetation. With reference to pipeline corridors in Colombia, South America and Georgia, southeast Europe, this paper presents a procedure for evaluating the risk of erosion during the period between reinstatement of the soil and vegetation establishment, and for comparing the effectiveness of different methods of erosion control.

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