Interpretation of autumn soil tests for hazelnut

Abstract

The suitability of soil-test analyses for fertilizer recommendations for hazelnuts was assessed by detailed examinations of correlations with corresponding leaf-tissue concentrations in an orchard survey study. Correlations were examined only where optimum leaf-tissue nutrient concentrations had previously been established (i.e. N, P, K, S, Mg and Ca). Soil nitrate concentrations tended to increase substantially and relatively consistently in orchards where leaf N concentrations were greater than the optimum range, showing that soil and leaf analyses can be used for fertilizer recommendations for conservation and environmental as well as production considerations. Since most of the trees of the orchards in the study had P that was at or above adequate amounts, only limited conclusions could be made for soil P tests. Data from this survey and other literature showed that hazelnut trees can obtain adequate P from soils that have relatively low Bray-1 extractable P. Ammonium acetate extraction provides a reasonably good estimate of the K and Mg that are available to hazelnuts, and, for both nutrients, K and Mg fertilizer should be recommended for hazelnut (compared with many other crops) when soil-test analyses are relatively high. Ammonium acetate extracted considerable Ca from the soil and the amount extracted was not correlated with the concentration of Ca measured in the leaves. Calcium chloride (which extracts only unadsorbed sulphate) was a relatively poor extractant for available S because of the occurrence of sulphate adsorption in these soils. A surface 15-cm soil sample was adequate for most of the nutrients measured, but supplementation with subsurface analyses would improve nitrate, and possibly subsurface S should be included in the development of a soil test for S Soil testing is necessary to determine whether nutrients are building up in the soil. Also, only soil testing can be used for analysis-based recommendations prior to tree planting. Key words: Hazelnuts, Corylus avellana, filbert, nitrogen, phosphorus, potassium