Response of Maize to Different Soil Residual Phosphorus Conditions

Abstract

Large reserves of phosphorus (P) in Brazilian soils can be potentially used by crops. However, it is not well known how different tillage systems and past P fertilizer management strategies affect legacy P utilization. A trial was conducted in an Oxisol (Rhodic Haplustox) at Embrapa Cerrados, Federal District, Brazil to investigate the effects of different soil residual P conditions on maize yield. For 17 yr, annual summer crops were fertilized with 80 kg ha−1 yr−1 P2O5 in a split‐plot design consisting of eight treatments: no‐tillage system (NT) or conventional tillage (CT), fertilized with triple superphosphate (TSP) or reactive rock phosphate (RRP), applied to the crop furrow or broadcast. P fertilization was then discontinued and maize grown for 4 seasons relied on the residual soil P under NT or CT. Residual P use efficiency, calculated as a ratio between grain yield and total residual P in the soil, was greater under NT than CT, as a consequence of higher availability of P determined by Bray‐1, Mehlich‐1 and Olsen methods. Past use of RRP sustained better yields and higher residual P use efficiency, especially in NT, due to its lower solubilizing rate. P placement strategy did not change residual P use efficiency. We recommend assess amount of available P to identify sites in which residual P may sustain crop needs. Finally, the use of RRP, especially under NT, is a recommended management strategy for reducing phosphate fertilizer demand in heavily weathered soils of Central Brazil. Core Ideas No‐tillage system promotes efficient P use, especially after discontinued P supply. Due to slow solubilizing rate, reactive rock phosphate sustains better residual P availability. Fertilizer placement did not influence residual P use efficiency.

Long‐term phosphate fertilization strategies evaluation in a Brazilian Oxisol

“…Despite these concerns, Oliveira et al. (2019) affirm all these three methods can all adequately assess STP, provided that results are interpreted considering the respective P source.…”

“…The aforementioned problems were discussed by Oliveira et al (2019) in the same soil type. The authors noticed similar underestimation between Bray-1 and Olsen tests and an overestimation of Mehlich-1 P when dealing with RRP fertilized soils.…”

Distribution of Soil Phosphorus Fractions as a Function of Long-Term Soil Tillage and Phosphate Fertilization Management

“…RRP results in a high accumulation of these calcium phosphates and also P forms adsorbed on Fe and Al oxides and clay minerals of lower lability compared to TSP, evidenced by both the higher levels of HCl Pi and NaOH 0.5 M Pi, as previously reported by Soltangheisi et al (2018) in a similar Oxisol. Although these fractions are considered to be of lower lability, an elevated residual effect and P use efficiency was observed from RRP fertilization after cultivating this area without P input during successive corn crops (de Oliveira et al, 2019).…”

“…Also, depending on the soil layer, the most common order in which the factors influenced P fractions was first the soil management system, then the source of phosphate fertilizer, and finally the method of application. The interaction of phosphate fertilizer management systems with the soil management system is probably related to the fact that CT and NT may provide different degrees of soil/fertilizer contact, possibly modifying the dynamics of the fertilizer solubilization, especially for slowly soluble sources like RRP, which requires more time and greater soil surface contact for dissolution (Pavinato et al, 2017;de Oliveira et al, 2019). In NT, the fertilizer application method directly influences P contents in the different soil layers, while CT minimizes the effect of the placement of the phosphate applied in previous growing seasons.…”

“…This high P input is usually called corrective P fertilization, and P rates depend on STP and soil buffer capacity (Sousa et al, 2010). Excessive fertilization after the P correction phase or incorrect agricultural practices, as observed for soybean monoculture under conventional tillage (de Oliveira et al, 2019) and/or in the absence of cover crop in the rotation system (Sousa et al, 2010), may promote even more legacy P accumulation, with very low P use efficiency under these production systems.…”