Determining Mehlich‐3 and DTPA extractable soil zinc optimum economic threshold for maize

MARTÍNEZ CUESTA, NICOLÁS; WYNGAARD, NICOLÁS; SAÍNZ ROZAS, HERNÁN; REUSSI CALVO, NAHUEL; CARCIOCHI, WALTER; EYHERABIDE, MERCEDES; COLAZO, JUAN CRUZ; BARRACO, MIRIAM; GUERTAL, ELIZABETH A.; BARBIERI, PABLO

SOIL USE AND MANAGEMENT

WILEY-BLACKWELL PUBLISHING, INC

Año: 2020

0266-0032

Maize (Zea mays L.) is one of the most susceptible crops to zinc (Zn) deficiency. However, inmuch of the world, soil Zn tests are poorly calibrated, and thus determining a critical soil test level forZn is challenging. The objectives of this study were to: i) produce a field calibration of the ZnMehlich-3 (M3-Zn) method for predicting maize grain yield response to Zn fertilizer application, ii)compare the capacity of DTPA extractable Zn (DTPA-Zn) with M3-Zn for predicting the response ofmaize yield to Zn fertilizer, iii) determine whether inclusion of soil pH, organic matter (SOM) andextractable phosphorus in a M3-Zn model improves its predictive capacity, and iv) evaluate aneconomic approach for determining soil Zn thresholds. We conducted 55 field experiments covering a wide range of edaphic and climatic conditions. Maize responded to Zn fertilizer in 29% of the trials. The capacity of M3-Zn and DTPA-Zn to predict relative yield of maize was similar. Inclusion of other soil variables (pH, extractable phosphorus, and SOM) did not or only slightly improve the prediction of M3-Zn. Based on the relationship between M3-Zn and DTPA-Zn (R2 = 0.89), one test can be predicted from the other without affecting the calibration. The M3-Zn ?economic threshold? ranged from 0.98 to 2.79 mg kg-1, while for DTPA-Zn it varied from 0.41 to 1.61 mg kg-1. The broad range of economic thresholds shows that differences in maize productivity and grain price between regions and seasons make establishing a single Zn threshold for all economic-productive situations inappropriate.