
%0 Journal Article
%A Cripps, JEL 
%T Response of apple trees to soil applications of phosphorus, nitrogen and potassium
%J Australian Journal of Experimental Agriculture
%D 1987/12/01
%V 27
%N 6
%P 909-914
%K 
%R https://doi.org/10.1071/EA9870909
%U https://www.publish.csiro.au/paper/EA9870909 
%X An experiment was conducted at Manjimup Research Station in Western Australia from 1973 to 1982 to determine the optimum rates of fertilizer applications for apple trees (Granny Smith/MM.104 and Hi Early Red Delicious/MM.104) growing in a P-deficient soil (about 6 mg/g bicarbonate-extractable P). The trees were planted at 6.1 multiply 6.1 m spacings. Superphosphate at 5 or 8 kg/tree consistently increased fruit set, but the increase varied from year to year from 8 to 91%. Weight of prunings increased by 24-29% and tree height multiply width by 11-16%. When results were averaged over both cultivars, weight of fruits harvested from 1973 to 1982 was increased from 853 to 1226 kg/tree by superphosphate application at 5 kg/tree. Ammonium nitrate applied at up to 4 kg/tree gave small non-significant increases in growth and no increase in weight of fruits harvested for Granny Smith, but the weight of the Red Delicious crop rose by 11%. No response to potassium chloride at 1 kg/tree was found. P fertilizer application increased P concentration in the first fully mature leaves of Granny Smith trees from approximately 0.14% to 0.17-0.19% and in Red Delicious leaves from 0.17 to 0.20-0.21%. N fertilizer application increased N concentration in Granny Smith leaves from approximately 2.3 to 2.5%. Lack of P was the main limiting factor on growth and cropping and it is suggested that the importance of P nutrition in Western Australian apple orchards has been underestimated. 
