Phosphorus and potassium soil test and nitrogen leaf analysis as a base for citrus fertilization

Authors: Quaggio J.A.; Cantarella H.; van Raij B.

Source: Nutrient Cycling in Agroecosystems, Volume 52, Number 1, September 1998 , pp. 67-74(8)

Publisher: Springer

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Abstract:

A network of six NPK long-term field trials was carried out on different soils of citrus-producing regions of São Paulo state, Brazil, in order to estimate quantitative relations of fruit yield to NPK fertilization and to determine parameters for fertilizer recommendation based on soil testing and leaf analysis. The experiments were set up in an incomplete factorial design 1/2 4^3 with 32 treatments, with four yearly rates of N (30, 100, 170 and 240 kg N/ha), P (9, 27, 45 and 63 kg P/ha) and K (25, 91, 157 and 223 kg K/ha). Four to seven harvests were recorded for the six experiments. Response surfaces of the type y = bo + b_1N + b_11N^2 + b_2P + b_22P^2 + b_3K + b_33K^2 + b_12NP + b_13NK + b_23PK were adjusted to the average yields of each trial. Correlation were established for yield increases, expressed as relative yields, and results of soil analysis of P and K, and leaf analysis of N. Soil samples taken at 0-20 cm depth in the beginning of each experiment were analyzed for resin extractable P and exchangeable K using an ion-exchange resin procedure. Yield responses for phosphorus and potassium applications were observed respectively in soils with less than 20 mg dm^-3 of P and 20 mmol_c dm^-3 of K^+. Yield responses to nitrogen were related to the total content of nitrogen in leaves, being largest for N values of 23 g kg^-1 and smallest for N of 28 kg^-1. With these field information, a practical approach for fertilizer recommendation for citrus, based on soil analysis for P and K and leaf analysis for N, was developed.

Keywords: citrus; soil analysis; leaf analysis; calibration; fertilizer response; fertilizer recommendation

Language: English

Document Type: Regular paper

Affiliations: 1: Section of Soil Fertility and Plant Nutrition, Instituto Agronômico, Caixa Postal 28, 13001-970 Campinas, SP, Brazil

Publication date: 1998-09-01

Phosphorus and potassium soil test and nitrogen leaf analysis as a base for citrus fertilization

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