Long-term management strategies to optimize phosphorus utilization in a tropical maize and soybean succession

Abstract

Context or problem

The efficiency of phosphorus (P) input utilization in Brazilian agricultural systems is low (50 %) but can be improved by adopting appropriate management strategies.

Objective or research question

The objective of this study was to assess and quantify the combined long-term effects of soil tillage and rates and forms of P fertilizer inputs on soybean [Glycine max (L.) Merr.] and maize (Zea mays L.) yield, P use efficiency and soil P availability in a high P-fixing tropical soil.

Methods

A comprehensive 22-year field experiment was undertaken in a Brazilian Cerrado soil with two soil tillage systems (conventional-CT and no-tillage-NT) combined with five P fertilizer management, being two sources of P [triple superphosphate (TSP) and Gafsa reactive phosphate rock (RPR)], under two annual rates of P (22 and 44 kg ha^–1), and one control (no P application). Measurements included crop yield, removed P, partial P balance, and soil P [total P, legacy P, and labile P (Mehlich-3)].

Results

The NT and CT systems were equally productive. Plant yield responses were similar for TSP and RPR when 44 kg ha^–1 of P was applied annually, although maize grain yield was 6 % higher for TSP compared with RPR at the lower rate of P application (22 kg ha^–1 yr^–1of P). The low P input rate was not enough to meet crop demand since the partial P balance was 131 % compared with 80 % for the high P input rate, both under TSP application. The same behavior was verified under RPR application, being 115 % compared with 74 % for the low and high rate of P, respectively. In the soil, CT system showed narrower differences between treatments, with a homogeneous distribution of P in depth compared with NT, while the NT system resulted in enhanced P accumulation in the topsoil, especially at the high rate of P fertilizer input.

Conclusions

Our findings indicate that the use of an intermediate rate between 22 and 44 kg ha^–1 yr^–1 of P by RPR or TSP, especially under NT, is a recommended management strategy to optimize P utilization by maize and soybean while increase soil P bioavailability in a high P fixing tropical soil.

Implications or significance

This study confirms that improving phosphate fertilization and soil management practices is key to ensuring the sustainable and efficient utilization of P in tropical agricultural systems.