Study On Soil Phosphorus Nutrition And Enrichment Of Transformation In Loess Plateau

Increasing fertilizer use efficiency and content of available phosphorus in soil are the key issues of dry farming and modern agriculture. A research of dynamics of phosphorus accumulation and utilization efficiency of winter wheat, fertilization on soil particle composition and phosphorus enrichment, different fertilization methods on content of available phosphorus in soil profile on dry-land in Loess Plateau and treat of incubation experiments of the relationship between available phosphorus content and soil water, temperature in laboratory. The main conclusions were drawn as follows:Maintain the soil nutrient balance is a prerequisite to keep land productivity, but high fertilizer can not achieve the desired crop yield and economic benefits. The effect of phosphorus content of winter wheat plants under phosphate fertilizer presented a "V" shape curve. Phosphorus content was the highest during the early growth period of winter wheat, and decreased with the crop growth, and reached the minimum in the filling stage, then increased. Phosphorus of winter wheat accumulated mainly in two stages which are jointing stage - flowering and filling stages– mature, an important role of good growth on wheat to ensure the supply of phosphorus in the two stages. From phosphorus utilization efficiency, yield and other indicators, in the case of application of nitrogen fertilizer 90 kg/hm², phosphate fertilizer should be controlled a reasonable range in 45⁹0 kg/hm².In the long-term experiment, the smaller soil particle was the higher the proportion of soil aggregates was in four fertilization treatments, but the different fertilizer treatments would influence the proportion of the same particle size. The combined application of nitrogen fertilizer, organic fertilizer on the basis of a single P application (NP,PM,NPM), would help to increase the <0.25 mm proportion of aggregates, the NPM was the most obvious. The long-term application of organic fertilizer could improve available phosphorus in soil aggregates, in same time the proportion of the water-soluble phosphorus in available phosphorus of the soil aggregates may be increased. Available phosphorus in the soil (including Olsen-P, water-soluble phosphorus) mainly enriched in the <2 mm soil aggregates, the highest enrichment rate of available phosphorus was in <0.25 mm soil aggregates. The combined application of nitrogen and phosphorus fertilizer(NP) or nitrogen, phosphorus and organic fertilizer(NPM) could significantly improve enrichment rate of available phosphorus in <0.25 mm soil aggregates, but the application of phosphorus and organic fertilizer(PM) could increase enrichment rate of available phosphorus in 0.25～2 mm soil aggregates.In 0¹00cm soil layer, the available phosphorus content of different fertilization treatments into crop rotation showed a parabolic trend. In the topsoil (0²0cm) the Olsen-P content was the highest and decreases with the soil depth, and all treatments in the subsoil (below 40cm) no significant difference into crop rotation. It seems that the soil phosphorus was more likely to leaching in the organic fertilizer treatment for which obviously improved the ratio of water-soluble phosphorus and Olsen-P. The ratio of water-soluble phosphorus and Olsen-P is also large in bare land on the long-term experiment leading to soil phosphorus and leach for there was no planting. Soil phosphorus also easily leach in the deep profile in the M treatment. Consequently, soil phosphorus leaching may have occurred in bare land, N treatment and M treatment, with a high ratio of water-soluble phosphorus it has a high risk of leaching in deep soil.The results of long-term fertilizer test show that the topsoil has the highest phosphorus content in each treatment and the phosphorus content decreased as the deepening of soil. Rapidly-available phosphorus content has a significant difference in top soil (0²0cm) due to different fertilizing amount among different treatment, while no obvious difference in deep layer, soil rapidly-available phosphorus content has not increased in 20⁶0cm layer in the high concentration phosphorus fertilizer treatment, the content in the N₉₀P₁₃₅ treatment and N₉₀P₁₈₀ treatment increased less than 1ppm compared to that in the N₉₀P₉₀ treatment. Soil water-soluble phosphorus content has the similar trend with soil rapidly-available phosphorus content among the treatments that is the topsoil has the highest phosphorus content and which decreased as the deepening of soil. Soil water-soluble phosphorus content in the top soil increased as the increase of phosphorus fertilizer amount, the highest content was 1.398mg/kg when 180kg/hm² phosphorus fertilizer was used, which was 15 times those in the N treatment.Different soil moisture had a little influence in content difference on soil water-soluble phosphorus content and soil rapidly-available phosphorus content in the same temperature, It appears a decline trend in the whole. In the same soil moisture condition, soil water-soluble phosphorus content and soil rapidly-available phosphorus content appears a drop in different temperature with a small increase while no effect to the whole trend.In the same soil moisture condition, soil effective phosphorus content decreased with the temperature raised from 5℃to 15℃while the effective phosphorus content in 25℃was 1time those in 15℃, the ratio of effective phosphorus in 35℃and effective phosphorus in 25℃is less than one. The change trend of Q₁₀ was increased after a reduce by every 10℃, there was a relatively highest value in 25℃, then it was decreased with the temperature increased.