Is the Lack of Response of Maize to Fertilization in Soils with Low Bray1-P Related to Labile Organic Phosphorus?

APPELHANS, STEFANIA C.; BARBAGELATA, PEDRO A.; MELCHIORI, RICARDO J. M.; GUTIERREZ BOEM, FLAVIO H.; CAVIGLIA, OCTAVIO P.

Journal of Soil Science and Plant Nutrition

Springer

Año: 2021

0718-9508

The usual soil test phosphorus(P) neglects the P supply from labile organic P (Po) fractions, which couldexplain the nonresponse of maize (Zeamays L.) in sites with soil Ptesting below the critical level. We aim to determine Po and inorganic P (Pi)in NaHCO3 extracts and in the coarse soil fraction (hereinafter,CF) from responsive and nonresponsive sites to P fertilization in maize. Wethen compare the classification errors of the Cate and Nelson method bycomparing the relationship between maize relative yield and the soil Bray1-Pconcentration vs. the new proposed indices. The study included responsive andnonresponsive sites to P fertilization carried out across the Pampas Region inthe center-east of Argentina. Treatments included four P fertilization rates:0, 12, 24, and 36 kg P ha-1.The experiments were laid out in a randomized complete block design with three replicates.We determined Bray1-P, Pi, and Po in NaHCO3 extractsand in the coarse soil fraction. Sites non-responsive to P fertilization andwith Bray1-P concentrations below the critical level showed 70% more Po in thecoarse soil fraction (Po-CF) than sites with high crop response and similarBray1-P level. However, Po-Bic alone did not improve the relationship withmaize relative yield. Po-CF and Bray1-P included in a soil integrative P indeximproved the prediction of crop response to P fertilization and reducedclassification errors, which suggests that Po-CF is a source of available P forthe crops. The novelty reported in this study was to demonstrate the organic Pcontribution to relative yield by including it into an integrative soiltesting. We find that nonresponsive sites to P fertilization, with low Bray1-P,were correctly classified when including Po-CF in a new soil test P. Improvementsin the P fertilization diagnostic prescription tool contribute to an increasein economic profit and reduce environmental impact.