| Water shortage is the main limiting factor for crop productivity of dryland farming area in Loess Plateau. So how to improve water use efficiency ( WUE ) of crops, which is using the limited water to increase yield, is very important . The effects of organic fertilizer and planting density on plant growth and water use were studied under field condition. And the growth and WUE changes of spring maize under four cultivation patterns (include varieties, fertilizer, planting density and mulching) were discussed. The results are as follows:1. Organic fertilizer treatment didn't show obvious stimulative effect on root growth and function of spring maize. Instead, the whole root length and surface area in 30-100cm deep soil layer of organic fertilizer treatments were lower than the controls at pre-tasselling stage. At waxen maturity stage, base organic fertilizer reduced root length, surface area and dry weight in deeper soil and at the position of 1/4 row space, 1/2 row space, under plastic mulch which were farther from plant, so it restricted plant to use water and nutrient resources on a lager scale of soil. Also organic fertilizer didn't show obvious roles of maintaining root function and defering root senility.2. The facilitation of organic fertilizer was mainly expressed at overground part at early growth stage. Base organic fertilizer significantly increased height, leaf area per plant before silking stage, and increased photosynthesis at seeding stage and silking stage, resulting in a significant higher dry matter. Organic fertilizer treatment also advanced transpiration at silking stage, and increased water consumption from seeding stage to silking stage. The effects of organic fertilizer were weaker at later stage. The difference of height, leaf area per plant, LAI and Pn between organic fertilizer treatment and controls was not significant, and so do the yield. The higher water consumption of organic fertilizer treatment leaded to reduce WUE.3. The increase of planting density provided favorable conditions to advance yield because it increased LAI and spikes. The increase of planting density inevitably intensified intraspecies competition, because the water and nutrient resources were limited. The increase of density reduced root growth in plough layer and at planting position, but the difference of water uptake was not significant. Root showed some flexibility by increasing water uptake function per surface area. But high density treatment reduced Pn, and then reduced biomass per plant and grain weight per spike. The corn yield was also reduced. The increase of density decreased WUE because planting density had no significant effect on water consumption. The limit of resources must be considered when increased planting density in field.4. Because of the old maize varieties, low planting density, fertilizer inputs shortage, without mulch covering, traditional cultivation pattern in dryland leaded to lower Pn and slower overground part growth at early stage. What's more, the root growth was also slower than other cultivation patterns, especially in deep soil layer. Though low planting density and weak intraspecies competition leaded to faster growth rate, higher biomass per plant and grain weight per spike at later stage, the yield and WUE of traditional cultivation pattern were still lower. So yield and WUE could significantly improve by selecting good varieties, reasonable increase planting density, mulching, increasing fertilizer inputs and bettering application mode.5. Each cultivation measures affected each other in field condition. The effect of combining application of organic and inorganic fertilizer on increasing yield and WUE was significantly higher than only organic or inorganic fertilizer application. Increasing fertilizer inputs, fertilization balance, changing basal application into dressing and so on could efficiently reduce the loss of intraspecific completion, and be helpful for the increase of yield and WUE. |
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