Long-term phosphorus fertilization of wheat, soybean and maize on Mollisols: Soil test trends, critical levels and balances

SUCUNZA, FA; ALVAREZ R, GUTIERREZ BOEM FH, RUBIO G.; GARCIA FO; BOXLER M; RUBIO G

EUROPEAN JOURNAL OF AGRONOMY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018 vol. 96 p. 87 - 95

1161-0301

Few reportshave compared the P critical level between different crops under equivalentgrowing conditions and the impact of P balance and P fertilization practices onthe long term dynamics of soil available P. The objectives of this study were:i) to determine and compare, under similar field conditions, the P criticalvalues for soybean, maize and wheat; and ii) to evaluate the effect oflong-term application of P fertilizer on P balance and soil-test P. Resultsfrom a long-term experiment (2000/01 and 2013/14) involving soybean, maize andwheat crops in five experimental sites located at the Pampean Region(Argentina) were analyzed. Phosphorus levels included a ?P treatment without P applicationand a +P treatment with continuous P fertilization (annual average 37 kg Pha-1).Thecritical Bray-P thresholds were 14.3, 12.4 and 19 mg kg-1 for soybean, maizeand wheat, respectively.   The rate ofdecline of the Bray-P pool in the ?P treatments was described by an exponentialdecay function common to the five study sites. Obtained results indicated thata net extraction of 327 kg P per hectare is needed to reduce their initialBray-P values by half, regardless of the initial soil Bray-P value. The soilsfertilized with P showed a significant and linear increase in Bray-P. It waspossible to fit a single function after pooling the data of the five sites.This combined function indicated that 3.2 kg P ha-1 were necessary to increaseBray- P in 1 mg kg-1. Obtained data on crop P critical levels and rates atwhich soil-test P declines or increases according to the P balance constitutesa useful tool for sustainable use of P resources in Mollisols and related soilunits. They can help to monitor future changes of soil P levels and to estimatethe P demand of croplands.