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Evaluation Of A Controlled Release N-P Fertilizer Using A Modified Drill For Variable Rate Fertilization
1R. A. Ortega, 2J. F. Reyes, 2W. Esquivel, 3J. Orellana
1. Universidad Federico Santa Mar
2. Universidad de Concepci
3. COMPOAGRO Chile Ltda.

Base NP or NPK fertilization is a common practice in cereal production in Chile. Usually, a physical NPK blend is band applied with the seed at planting with the drill. Normal fertilizer rates vary from 400 to 500 kg ha-1; however, there is a tendency in the market to move from physical blend towards chemical blends (monogranule) and, more recently, to controlled release fertilizers (CRF). The CRF are usually recommended at very low rates, varying from 70 to 120 kg ha-1, however this rates are difficult to apply with existing fertilizer systems controlled by the drill’s wheel. The present work had for objective to evaluate the performance of the CRF Basacote P-max using a modified cereal drill capable of variable rate (VR) fertilization. A field trial was designed to evaluate the performance of the CRF at low rates as compared to a physical blend (PB) at normal rates. Soil was grid-sampled and fertility maps were developed; a prescription map with the best physical NP blend was developed for the whole field; a similar map was developed for the CRF. Four treatments were evaluated: CRF uniform, CRF variable, PB uniform, and PB variable in a strip design with three replications. Application accuracy as well as agronomic variables, including yield and test weight, were measured. Results indicate that is technically feasible to apply low CRF rates when controlling the drill with a VR system, and that the performance of CRF was equal or better than a physical blend, with all its advantages from the technical and operational stand points.

Keyword: Variable rate, controlled release fertilizers, fertilizer blends, wheat