Soil heterotrophic respiration and nutrient mineralization are strongly affected by environmental conditions, in particular by moisture fluctuations triggered by rainfall events. When soil moisture decreases, so does decomposers' activity, with microfauna generally undergoing stress sooner than bacteria and fungi. Despite differences in the responses of individual decomposer groups to moisture availability (e.g., bacteria are typically more sensitive than fungi to water stress), we show that responses of decomposers at the community level are different in soils and surface litter, but similar across biomes and climates. This results in a nearly constant soil-moisture threshold corresponding to the point when biological activity ceases, at a water potential of about -14 MPa in mineral soils and -36 MPa in surface litter. This threshold is shown to be comparable to the soil moisture value where solute diffusion becomes strongly inhibited in soil, while in litter it is dehydration rather than diffusion that likely limits biological activity around the stress point. Because of these intrinsic constraints and lack of adaptation to different hydro-climatic regimes, changes in rainfall patterns (primary drivers of the soil moisture balance) may have dramatic impacts on soil carbon and nutrient cycling.

The study evaluated effects of drought on some agro-morphological traits of 60 rice genotypes comprising 54 introgression lines with their parents, IR 64 (Oryza sativa) and TOG 5681 (Oryza glaberrima) and four NERICA-L varieties developed from the same parents for comparison. The genotypes were subjected either to full irrigation from sowing to maturity (control) or to 21-day drought applied by stopping irrigation from the 45th day after sowing (DAS) onward (drought) in the dry seasons of 2006 and 2007-2008. Plant height, spikelet fertility, grain yield and leaf area at harvesting were consistently reduced by drought in both seasons. Values of leaf temperature, leaf rolling, leaf tip drying, leaf blast, days from seeding to flowering and maturity were higher under drought. The results on SPAD and number of tillers were not consistent. Significant relationship (P<0.05) was observed between all traits evaluated and grain yield under drought. Introgression lines, SEN-L13-2, MPL-15-3, SEN-L10-1, SEN-L26-3 and SEN-L21-2 showed significantly higher yield than the highest yield NERICA-L variety (all of them had higher yield than the parents). Among them, SEN-L13-2 showed the lowest yield loss by drought and MPL-15-3 had high yield potential and considerably low yield loss by drought.Copyright © 2011. Published by Elsevier Ireland Ltd.

以皖稻153、两优0293等9个品种为材料，利用土壤水势张力计控制土壤水分，在分蘖期和孕穗期进行自然干旱处理与常规水分管理，研究干旱对不同品种水稻生长、生理特性和产量的影响。结果表明：分蘖期和孕穗期水稻土壤水势控制在-75kPa左右10d时间，对水稻的株高、分蘖动态、绿叶面积、叶片水势和叶片含水量均产生明显影响；水稻植株生理指标对干旱胁迫响应明显，MDA浓度、POD活性、SOD活性、可溶性糖含量和脯氨酸含量均有不同程度增加，且差异均达极显著水平；从产量上看，新两优6号、新两优香4号和两优0293三个品种抗旱性较强，其中，新两优6号干旱处理分别比对照减产最小，仅是3.32%和4.27%；新两优香4号和两优0293两个品种虽然也减产，但减产幅度在10%以内。

Using 9 rice varieties as materials,this paper studied the effects of soil water stress (soil water potential) on the growth and physiological feature and yield by pot experiment by manual rigorously controlling soil potential with tension-meter.The results indicated that the plant height, tillering dynamics, green leaf area, leaf potential, and leaf water content were affected to different degree when the soil water potential (SWP) reduced to - 75 kPa during different growth periods.Under drought stress,leaves of 4 varieties of Hydrangea of different physiological changes occur,content of Methane Dicarboxylic Aldehyde and POD and SOD activity and proline and total soluble sugar marly all increase.The difference reached to a most significant level.As for yield, the drought resistance of Xinliangyouxiang 4, Xinliangyou6 and Liangyou0293 are strong.Yield of Xinliangyouxiang4 for the drought treatment were lower than the CK by 3.32% and 4.27%,the other two decreased within 10%.

为进一步探明水稻生长与水分养分之间作用机制，充分发挥水肥耦合效应，在湖北省灌溉试验中心站开展了水肥综合调控模式试验研究。设置了常规淹灌模式（W0）、间歇灌溉模式（W1）、蓄雨型间歇灌溉模式（W2）3种灌溉模式；不施氮肥处理（N0）、当地实际施氮水平（N1）、当地施氮水平的75%（N2）3种施氮水平；基肥+一次追肥（F1）、基肥+二次追肥（F2）2种施肥方式。结果表明，与淹灌相比，间歇灌溉有利于水稻后期生长及高产，总氮排放负荷减少26%、总磷减少11%，氮肥利用率提高5.2%；与间歇灌溉相比，蓄雨型间歇灌溉会促进水稻全生育期生长，但后期茎叶过盛使产量略有减少，总氮排放负荷减少29%、总磷减少39%，氮肥利用率相当；在一定范围内增加施氮量可促进水稻的生长发育与高产；高施氮量下增加追肥次数可促进水稻后期生长与高产，但低施氮量下增加追肥次数可能会产生相反效果。

In order to further explore the mechanism between rice growth and water nutrients, give full play to the coupling effect of water and fertilizer, the experimental study on the comprehensive regulation of water and fertilizer was carried out at Hubei Provincial Central Station. Three irrigation modes were set up: conventional flooding irrigation mode (W0), intermittent irrigation mode (W1), and rain-storing intermittent irrigation mode (W2), as well as three levels of nitrogen application: no nitrogen fertilizer treatment (N0), local actual nitrogen level (N1), local application nitrogen level 75% (N2); There are two kinds of fertilization methods: base fertilizer + primary topdressing (F1), base fertilizer + secondary topdressing (F2). The test results show that compared with flooding irrigation mode (W0), intermittent irrigation mode is beneficial to the late growth and high yield of rice, the total nitrogen emission load is reduced by 26%, the total phosphorus is reduced by 11%, and the utilization rate of nitrogen fertilizer is increased by 5.2%; Compared with intermittent irrigation mode, rain-storing intermittent irrigation mode will promote the growth of rice during the whole growth period, but in the later stage, excessive stems and leaves will slightly reduce the yield, total nitrogen emission load decreased 29%, total phosphorus decreased 39%, and the nitrogen fertilizer utilization rate is equivalent; Increasing the amount of nitrogen in a certain range can promote the growth and high yield of rice; And increasing the number of topdressing under high nitrogen can promote the late growth and high yield of rice, but increasing the number of topdressing under low nitrogen may have the opposite effect.