Local de aplicação do fósforo, sistema radicular e produtividade da cultura da soja em plantio direto

Abstract

Modern agriculture presents constant challenges, among them productive and economical. The target on greater productivity and efficiency in the field leads to improvements of techniques performed today. Before a production system such as no-till and its limitations, the management of fertilization, especially phosphorus, is highlighted. Therefore, fertilization management can alter the P uptake dynamic, as much as the plant's capacity to adapt to different environmental conditions. The field study consists of three steps, resulting from experiments conducted near Não-Me-Toque-RS (Field 1) and Sao-Sepe-RS (Field 2), Southern Brazil, during the agricultural year 2014/2015. The experimental conditions where the plants were evaluated had similar climate, incident solar radiation and relief characteristics, but different soil physical and chemical characteristics. The soil management system adopted in both experimental areas is no-till. The experimental design was a randomized complete blocks with four replicates and five treatments. Individual plot size was 15 m wide x 200 m long. The treatments consist of five P allocation depths: subsoiler + deep band (20 cm), subsoiler + in-furrow (10 cm), broadcast, in-furrow (10 cm), and above seed (0-5 cm). The phosphorus source used was triple superphosphate (0-42-0) at rate of 70 kg ha-1. The results are presented and discussed in the form of articles, and addressed aspects related to changes in root growth provided by the P placement (Article 1), use and balance of P in each P placement (Article 2) and the impact of P placement in water stress conditions (Article 3). Finally, for a general approach of the study it was necessary a discussion covering the three studies. Phosphorus deep band showed higher root growth at 20-25 cm depth, greater soil P recovery and use, and lower losses by water stress.