Phosphorus uptake and use efficiency of different cotton cultivars in savannah soil (Acrisol)

ABSTRACT Low soil phosphorus (P) is a limiting factor for plant growth in the Brazilian savannah, where P diffuses slowly and has a high fixation rate in soil (as Al-P and Fe-P). In this study, we investigated the variation in P uptake by different cotton cultivars grown in savannah soil. We conducted a greenhouse experiment using a fully factorial 2 x 17 randomized design with two P treatments (low P = 20 mg kg-1 and high P = 120 mg kg-1) and 17 cotton cultivars. The plants were potted in Acrisol soil labeled with radioisotope 32P. There was genetic variation in the P use efficiency among the cotton cultivars. The P treatments significantly influenced the dry weight of shoots (DWS), P accumulation, the specific activity of 32P, and the L-value (both the standardized and L-values discounted the P present in the cottonseed). Hierarchical clustering analysis classified the cotton cultivars into distinct, internally homogeneous clusters. Our results suggest that cotton cultivars could be selected to maximize P absorption efficiency in conditions of low plant-available P. The cultivars FMT 523, FM 910 and CNPA GO 2043 were the most responsive to P fertilization, while Barbadense 01, FM 966LL, IPR Jataí, BRS Aroeira and BRS Buriti were most efficient at absorbing plant-available P.

摘要
巴西热带稀树草原地区土壤磷素（P）有效性低下是限制植物生长的关键因子：该区域土壤中磷素扩散速率缓慢，且易与铝、铁结合形成难溶性的铝磷（Al-P）与铁磷（Fe-P），磷素固定率极高。本研究针对热带稀树草原土壤中种植的不同棉花品种的磷素吸收差异展开探究。
本研究采用2×17完全随机析因试验设计开展温室盆栽试验，设置2个磷素处理水平（低磷组：20 mg·kg⁻¹；高磷组：120 mg·kg⁻¹），共纳入17个供试棉花品种。试验所用盆栽基质为黏化老成土（Acrisol），并采用放射性同位素磷-32（³²P）进行标记。
供试棉花品种间的磷素利用效率存在显著遗传变异。磷素处理水平对植株地上部干重（DWS）、磷素累积量、³²P比活度以及L值（包含标准化L值与扣除棉籽磷素后的L值）均产生显著影响。层级聚类分析将供试棉花品种划分为多个组内均一、组间差异显著的聚类簇。
研究结果表明，可通过筛选适配棉花品种，在土壤有效磷含量低下的环境中最大化磷素吸收效率。其中FMT 523、FM 910与CNPA GO 2043三个品种对磷素施肥的响应效果最佳；而Barbadense 01、FM 966LL、IPR Jataí、BRS Aroeira以及BRS Buriti则对土壤有效磷的吸收利用效率最高。