Nitrogen, phosphorus and potassium fertilizers for potatoes in Cyprus

Abstract

SUMMARYA number of experiments to test the effects of N and P fertilizers and a few testing K fertilizer were carried out mainly with Arran Banner and Up-to-Date potatoes in the major potato-growing area of Cyprus (Kokkinoohoria). The optimum nitrogen rate, all applied at planting in January-February, was 60–120 kg N/ha with yields reaching 50 t/ha. Phosphorus increased yields in only 4 out of 21 trials. In two of these cases the soil contained 8 mg bicarbonate-extractable P/kg soil or less. In the other two cases the soil contained 34 and 56 mg P/kg but irrigation was erratic. In only one experiment where soil potassium was depleted to 222 mg exchangeable K/kg through continuous cropping with irrigated crops, without potassium fertilizer, was a clear response to K fertilizer obtained; this, however, is the first response to K fertilizer by any crop reported in a plain area of Cyprus.Concentration of NO2·N in the petiole of the first mature leaf from the top sampled at 80 days from planting under the 120 kg N/ha rate, beyond which seldom were yields increased, was about 0·5%. In the only experiment where a response to K was obtained, concentration of K in entire leaves sampled as above was about 2·5%.It is argued that since growers in this area have used heavy dressings of P and K over recent years, they will seldom get any benefit from applying more than a maintenance dose of 70 kg P and 150 kg K/ha to the potato crop. It is suggested that since in semiarid regions leaching is limited, soil tests of NO3 content can aid farmers in choosing the optimum amount of N fertilizer for each crop.