| The sustainable agriculture in Red Soils area of China is restricted severely by the seasonal drought in summer and water erosion in spring. During the period of agricultural structure adjustment, soil erosion is accelerated due to soil disturbancing frequently. The ideal soil and water conservation practies are the measures that not only are able to rapidly block water erosion in rainy season, but also reduce the seasonal drought hazards coming several tens days later in dry season.To accomplish proposed goals, the research area was established on newly mechanical ploughed slope field of Red Soil. Six treatments (Straw mulch, PAM, Contour hedgerow and combinated treatments) were tested in a randomized complete block design (RCBD) on the cultivated plots with peanut and three treatments (Straw mulch, PAM and control) were selected to two parent material of red soil on bare runoff plots The slope water circulation, soil water characteristic, soil drought degree (D) and the crop drought index (SDD) were monitored during erosion and seasonal drought period in each plot. According to the integration of lab and field experiments, we researched the effect and mechanisms on seasonal drought.The red soil water characteristic was changed by the rapidly water erosion blocking treatments. Soil moisture was increased and soil water retention properties were improved by using PAM and contour hedgerow treaments. The values of suction at 10-2 of soil specific water capacity were used to evaluate the performance of its water supply, we found soil treated with PAM or straw mulch have stronger ability to supply water than soil treated with sole or combined pasturage. Due to the abundant precipitation in rainy season, the differences of soil water retention characteristic and reduction of surface soil water evaporation among different treatments were not reflected on the soil water storage in rainy season. It meant the effect of water conservation using different treatments in the rainy season has no significant difference. However, in the drought season, water consumption rate shown the difference from different treatments, it is one of the mechanisms of the effect of soil water conservation.Temporal and spatial distribution of red soil moisture was affected by the rapid water erosion blocking treatments. PAM treatment could effectively increased soil water content in 30-40 cm and 40-50 cm soil layer, while the straw cover treatment compared to PAM was more effective to improve the surface 0-10cm layer of soil water content. Results from the spatial interpolation of soil moisture showed that, the slope soil moisture in different parts were improved comprehensively by the PAM and straw mulch treatment. The slope water microhabitat during the seasonal drought period was improved by the increase in spatial continuity of soil water.The water erosion blocking measures would not only slowing down Red soil seasonal drought but also reduce the drought degree of groundnut. From the rainy season to the dry season, the degree of soil drought (D) increased, drought degree of each treatment was less than the control. The effects of different water erosion blocking measures on drought degree were not the same. The straw mulch more effectively alleviated the surface soil drought than PAM, while the PAM was better in deeper soil layer. In term of the whole soil, PAM can mitigate the drought, while the Paspalum natatum has no significant effect. The water blocking measures also alleviated the drought of groundnut, and increased crop yields. However, its effect outcome on was not completely consistent with the reduction of the degree of soil drought, it is showed that other mechanisms besides soil moisture also possibly involved the reduction of crop drought degree.The combined application of different kinds of water erosion blocking measures could alleviate the seasonal drought. Sole application of lines in groundnut has no significant effect on drought. However, the combination treatments of Paspalum natatum and PAM had positive impact on groundnut growth. Straw mulch and PAM has different mechanisms to water conservation. This is presumed to be associated with the two measures can effectively reduce water erosion and seasonal drought.
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