| Water scarcity and droughts occur frequently in arid and semi-arid areas of China. Conventional plow and frequent operation of small machinery applied in this area have run more than20years, which led to strong hardpan, compaction soil layer, and poor soil physical property. Additionally, mineral fertilizers were commonly applied without straw or organic fertilizer returning to the soil. The soil nutrition and moisture preserving capability became weak. Therefore, field experiments were conducted in fluvo-aquic soil (clay) and cinnamon soil (loam) that were two major soil types in central and northern area of Shanxi province. The purpose of this research was to provide theoretical and practical basis for enhancing soil storage capacity and agricultural sustainable development of dryland. The main results were as follows:1Effects of sub-soiling and organic fertilizer application on soil physical and chemical characteristicsSub-soiling could break the plow layer and significantly reduced soil bulk density at10-30cm soil layer both in clay and loam soil. Sub-soiling also regulated soil porosity, including increasing soil total porosity, capillary porosity and non-capillary porosity at10-30cm soil layers in clay soil. Moreover, soil total porosity and capillary porosity at10-30cm soil layer, non-capillary porosity at20-30cm soil layer on loam soil were increased. Sub-soiling improved soil solid, liquid and gas phase conditions at20-30cm soil layer both on clay and loam. Sub-soiling with straw incorporated further optimized the farming environment, significantly reduced crust thickness and compaction of surface soil at the jointing stage of maize as well as alleviated soil hardening conditions of the farming ground and increased rainfall infiltration. Sub-soiling combinedwith straw incorporated, sub-soiling and organic fertilizer increased soil organic matter, total nitrogen, available phosphorus and available potassium content at0-30cm soil layer to different degrees.2Effects of sub-soiling and organic fertilizer application on soil moistureIn loam soil, the sub-soiling with straw incorporated and sub-soiling treatments increased soil moisture at0-120cm soil layer compared with the control treatment before sowing. The sub-soiling and straw crushing returning both significantly increased soil moisture over0-60cm soil layer at jointing and trumpeting stages of maize. The straw crushing returning significantly increased soil water moisture over0-60cm soil layer both at silking and milking stages of maize, but the sub-soiling is not so remarkable. The straw crushing returning also significantly increased soil moisture over0-200cm soil layer at maturity stage of maize, and the sub-soiling was notable as well.In clay soil, the sub-soiling treatment increased the soil moisture at0-200cm soil layer compared with the control treatment before sowing. But the soil moisture reduced remarkably by11.89%(p<0.05) at20～30cm soil layer under sub-soiling compared with the control. The reason might be that sub-soiling in spring could accelerate the loss of soil moisture of20-30cm soil layer. The sub-soiling significantly increased soil moisture over0-60cm soil layer at jointing stage of maize, but the different use levels of organic manure were not distinct and the interplay of those two elements were not as significant. The sub-soiling and the different use levels of organic manure were notable on soil moisture over0-60cm soil layer on trumpeting stage of maize, but the interplay of those two elements were significant. Among them, sub-soiling with medium and high organic manure had the best effect. The sub-soiling and the different use levels of organic manure were not remarkable on soil moisture over0-60cm soil layer at silking stage of maize, and the interplay of those two elements were not as significant too. The cause might be the high rainfall of this period so that farmland soil moisture was in a relatively saturated state. The different use levels of organic manure significantly increased soil moisture over0-60cm soil layer on milking stage of maize, but the sub-soiling was not prominent and the interplay of those two elements were not as significant. The sub-soiling and the different use levels of organic manure were outstanding over0-200cm soil layer on maturity stage of maize, but the interplay of those two elements were not significant.3Root distribution characters of maize under sub-soiling and organic fertilizer applicationCompared to the contrast, the root distribution in soil layer from0to20cm was relatively reduced, and the root dry weight, root length density, root surface area density and root volume density below20cm soil layer became greater under sub-soiling with straw incorporated and sub-soiling treatments. From the soil profile view, root dry weight density, root surface area density and root volume density below40cm soil layer under sub-soiling with straw incorporated treatment was greater than sub-soiling treatment. The reason might be that the good water and fertilization condition in this treatment promoted the root deeper growth and let the root distributed in the deeper soil layer.Volume of xylem sap was increased at silking stage after sub-soiling with straw incorporated and sub-soiling with the different use levels of organic manure treatments. Therefore, the measure of sub-soiling combined with different use levels of organic fertilizer can break the soil plough layer and build reasonable soil structures of the furrow soil. It was conducive to root fixing, alleviated the root growth space stress. The root distribution in the soil was reasonable. The root activity and ability of absorption water and nutrient were increased.4Maize leaf water status and photosynthesis response to sub-soiling and organic fertilizer applicationLeaf water potential and leaf relative water content were increased in different periods of maize growth under sub-soiling with straw incorporated and sub-soiling with organic manure. Meanwhile, above-mentioned treatments always maintained high Chlorophyll SPAD value of leaf at the early and middle stages of maize growth. The sub-soiling with straw incorporated, sub-soiling with medium and high use levels of organic manure and rotary tillage with high organic manure had significantly effective on reducing rate of the Chlorophyll SPAD value of leaf in maize later growth period. The results indicated that sub-soiling with straw or organic manure incorporated could postpone leaf senescence and thus advantageous to the output formatted.The Pn, Tr and Gs of maize were improved significantly by sub-soiling with straw incorporated. Results showed that the Pn, Tr and Gs of maize increased at different degrees after using of different levels organic manure at jointing, tasseling and milking stage of maize, and the sub-soiling was notable and the interplay of those two elements were not significant. 5Effects of sub-soiling and organic fertilizer application on maize growth and development, yield, quality and water use efficiencySub-soiling with straw incorporated and sub-soiling with medium and high use levels of organic manure significantly increased plant height, stem diameter and decreased the ratio of ear and plant height and LSI at the trumpeting, silking and filling stages of maize. At the same time, sub-soiling with straw incorporated and sub-soiling on loam improved the grain protein content, yield, water use efficiency and rain fall use efficiency to different degrees. Sub-soiling and the different use level of organic manure on clay treatments significantly increased maize yield, water use efficiency and rain fall use efficiency and the interplay of those two elements were not significant. |
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