Estratégias de absorção e utilização de fósforo por genótipos de soja

Abstract

Currently, crops such as soybeans are highly dependent on applying phosphate fertilizers. However, phosphorus (P) is a finite natural resource and proposing alternatives for P rational use is an urgent demand at a global level. Therefore, proposing studies that (a) help understand the mechanisms of P absorption and utilization adopted by soybean plants grown under low P availability; (b) evaluate the influence of low P availability in the soil on the partition and redistribution of the nutrient, investigating physiological markers of P deficiency during the crop cycle, and (c) verify changes in P forms in the rhizosphere soil and the tissues of soybean plants grown under low P availability; may help to select efficient genotypes and optimize P use through better management of fertilizers. The objective of this study was to investigate the P nutritional efficiency of soybeans based on physiological and morphological parameters and to evaluate changes in soil and plant tissues caused by low P availability in soils with different textures. Thus, three studies were carried out in a greenhouse (one in a hydroponic system and two in soil), using different levels of P availability. Study I showed that soybean genotypes with high P utilization efficiency (PUE) showed greater use of light energy and higher leaf area than the others. Furthermore, only the BMX 50i52 IPRO genotype was efficient in both P acquisition and utilization, as well as responsive to P. In addition, leaf area was a good indicator of P efficient genotypes. Study II revealed that soybean plants grown in soils unfertilized with P decreased their growth and altered the P redistribution and partitioning patterns within plant tissues. In addition, inorganic (Pi) and organic (Po) P concentrations decreased in plants grown on unfertilized Alfisol, while only Pi decreased in plants grown in unfertilized Oxisol. Similar to Study I, the leaf area was a physiological indicator sensitive to short-term P stress for soybeans. Finally, in Study III, we found that the inorganic P pool increased in the rhizosphere after soybean cultivation. However, our results showed that soil P pools with moderate and low lability, such as organic P and calcium-bound P, can also be accessed in the rhizosphere, even under high P availability. Additionally, soybean P uptake was closely related to changes in soil available P pool (Mehlich-3). Finally, we demonstrate the possibility of using plant variables as indicators of soil P changes. These results will help to increase the yield of soybean crop, reduce the use of phosphate fertilizers, reduce the risk of environmental contamination, and increase the profitability of soybean farmers.