干旱季节不同耕作制度下作物─红壤水势关系及其对干旱胁迫响应

RELATIONSHIP BETWEEN WATER POTENTIALS OF RED SOILAND CROP LEAVES UNDER FIVE FARMING SYSTEMS ANDTHEIR RESPONSES TO DROUGHT STRESS IN DRY SEASON

季节性干旱是南方红壤地区旱地农业生产中的主要障碍因素。本文报道了田间条件下作物土壤水势关系及其对干旱胁迫响应。结果表明ＳＰＡＣ中水势梯度为：叶气系统＞叶土系统＞７０ｃｍ以上土层，且约以１００倍左右递减，水势日变化结果表明免耕较常耕，窄垄较宽垄叶土水势差下降，水分胁迫更强；花生的耐旱性较强，大豆和玉米的则较弱；作物叶水势与土壤基质势呈正相关，可以用二项式表示。作物叶水势与不同土层土壤基质势关系表明，垄作处理作用层次更深，免耕处理仅与表层土壤基质势相关。土壤基质势和叶水势都随环境温度提高而降低；不同耕作制度改变了土壤温度和微气候，进而影响了水势的温度效应。结果说明高温和水分胁迫导致并加剧了红壤季节性干旱胁迫。

Seasonal drought is one of the main constraints to agricultural development ofupland in the area of red soil of China. The responses of crops under five farmingsystems to drought stress are reported in this paper. The differences of waterpotentials between air and crop leaves were about 100 times higher than thosebetween crop leaves and soil in the surface layer of 10cm. The differences betweenthe latter were around 100 times higher than those between soils in the layers of 10cmand 70cm as well. The differences of water potentials were lower in the treatments ofminimum tillage and narrow ridge tillage than those in the treatments of conventionaltillage and wide ridge tillage respectively, indicating the serious water stress in formertreatments. The results of diurnal variation of water potentials in soil-plant-atmospherecontinuum (SPAC) indicated that peanut is more tolerant to drought than soybean andcorn. Leaf water potential decreased with the increase of soil water potential and itsrelationship could be expressed by binomial equations. In the treatments of ridge tillage,leaf water potential was more related to the water potential of soil in deeper layersthan to that of soil surface in the treatment of minimum tillage. Water potentials ofsoils or leaves increased with the increase of soil and air temperatures respectively.The effect of temperature on water potentials of soils and leaves were affected byfarming practices and crop communities. Results showed that seasonal drought in theregion is caused by integration of water stress and high temperature.