Mechanisms Of Phosphorus Availability In The Rhizosphere With Different P-efficient Wheat Genotypes

A pot experiment on calcareous soil (Lu soil) and acid soil (Red soil) was carried out to investigate the impacts of two group different phosphorus (P)-efficient wheat genotypes on pH, acid phosphatase activity and P fractions in the rhizosphere at three rates of P fertilizer using a thin slicing technique. Four different P-efficient wheat genotypes were selected in this study and divided into two groups: Xiaoyan 54 and Jing 411, Luofulin and Zhongguochun. Xiaoyan 54 and Luofulin were high P-efficient wheat genotypes; Jing 411 and Zhongguochun were low P-efficient wheat genotypes. The purpose of this paper is to understand the mechanisms of phosphorus availability in the rhizosphere soil between different P-efficient wheat genotypes on different soil types. The results in this experiment were showed as follows:(1).The seedling growth of two group wheat genotypes was significantly different. On calcareous soil, the root growth of high P-efficient wheat genotype was significantly higher than that of low P-efficient wheat genotype at phosphorus efficient and sufficient conditions. Meanwhile on acid soil, the shoot growth of high P-efficient wheat genotypes was significantly higher than that of low P-efficient wheat genotypes under phosphorus deficient conditions.The total phosphorus uptake of high P-efficient wheat genotypes was significantly higher than that of low P-efficient wheat genotypes, which indicated that the ability of phosphorus uptake of high P-efficient wheat genotypes was stronger than that of low P-efficient wheat genotypes.(2). The rhizosphere pH of two group wheat genotypes was significantly different with soil types. In P deficient conditions, Xiaoyan 54 caused greater pH reduction in the zone 1～5 mm from the mesh compared with the bulk soil, while the Jing 411 reduction zone was 1～3 mm. Under P deficient conditions, the rhizosphere pH of Xiaoyan 54 on calcareous soil was significantly lower than that of Jing 411. While on acid soil, the rhizosphere pH of Xiaoyan 54 was slightly lower than Jing 411.The rhizosphere pH of two group wheat genotypes was decreased compared with the bulk soil, but the pH reduction range of two group wheat genotypes was differently due to soil types. On calcareous soil, the pH reduction range of high P-efficient wheat genotypes was higher than that of low P-efficient wheat genotypes, which can activation soil phosphorus. The results were differently on acid soil, the pH reduction range of high P-efficient wheat genotypes were lower than that of low P-efficient wheat genotypes, which maintain suitable rhizosphere pH inorder to retain P availability.(3). The rhizosphere soil phosphatase activity existed difference for two group wheat genotypes. Compared with the bulk soil, the phosphatase activity of acid and alkaline in the rhizosphere was increased with two group wheat genotypes, especially for acid phosphatase activity. Under P deficient conditions, the highest values of acid phosphatase activity was observed at root surface soil, and decreased with increasing rates of P applied.The acid phosphatase activity of root surface soil of two group wheat genotypes was differently due to soil types. On calcareous soil, the acid phosphatase activity of root surface soil at high P-efficient wheat genotypes was higher than that of low P-efficient wheat genotypes; while on acid soil, the acid phosphatase activity of root surface soil at Xiaoyan 54 was lower than that of Jing 411, and the acid phosphatase activity of root surface soil at Luofulin was higher than that of Zhongguochun.(4). The content of water soluble-P of different P-efficient wheat genotypes was differently due to soil types. The water-soluble P of root surface soil of Xiaoyan 54 was significantly lower than Jing 411 on calcareous soil; while on acid soil, the water-soluble phosphorus of root surface soil of Xiaoyan 54 was significantly higher than Jing 411. Reversely, the water-soluble phosphorus of root surface soil at Luofulin was significantly higher than Zhongguochun on calcareous soil and significantly lower than Zhongguochun on acid soil.