Physical and chemical soil variability in a characteristic Hop field of Galicia (Spain)

Abstract

The variability of the physical properties of the soil, as well as the nutritional levels, is a crucial aspect toward improving the management of hop cultivation, increasing its productivity. The European regulations that pursue a reduction in inputs, such as efficient control of nitrogenous fertilizers, require detailed studies to allow differential nutrition to be carried out. Specific fertilizer recommendations for the cultivation of hops depend on the type of soil and cultivar, and so they must be obtained based on soil analysis. Laboratory analyses are highly demanding in terms of time and cost, and so the existence of other analysis techniques should be explored. The determination of the soil apparent electrical conductivity (ECa) has shown a close relationship with various physical-chemical properties of the soil, for which the following objectives were established in this work: i) analyzing the relationships between ECa and the main physical-chemical parameters of the soil, and ii) evaluating the spatial variability of soil properties in a characteristic plot of hops. A soil sampling design was carried out, where the results of the soil samples show a great degree of spatial variability, with variables such as P and N, and with variation coefficients (CV) of > 50 %. Positive relationships (Spearman correlations) were obtained between C, N, and OM and ECa-H (ECa, 0.75 m), and a negative relationship was obtained with ECa-V (ECa, 1.5 m); moreover, a positive relation was obtained with the effective cation exchange capacity (eCEC) and ECa-H. The spatial distribution shows different patterns depending on the property represented, where areas with low levels of P and low pH are observed. Based on the relationships established between ECa and OM, and C and N, it is possible to monitor these parameters over the years. In the case of elements such as P, it is necessary to continue with a classical soil analysis, combined with foliar analysis. Areas with extreme values obtained in the study should be used as sampling areas to assess the nutrients and to proceed with their correction, when necessary.