Soil and Plant Analyses to Diagnose Hop Fields Irregular Growth

In cultivated fields, patches of poorly developed vegetation often appear without a clear indication of what is affecting the growth of the plants. The purpose of this study was to investigate the causes behind these irregularities in the hop (Humulus lupulus L.) fields of NE Portugal which are greatly reducing crop yield and farmers’ profits and to provide guidance to farmers as to appropriate remedial action. Patches of different levels of plant development were selected within hop fields and categorized according to plant vigour (weak, fair and good). Several soil properties were determined and related to the plant nutritional status and dry matter yield of different parts of the plant (hops, leaves, stems). Data was subjected to analysis of variance and principal component analysis. The results suggest that crop yield is reduced mostly due to poor soil aeration and excessive soil and tissue Mn and Fe levels. The plants from the plots of weaker vigour seem to be particularly affected by toxic levels of Mn and the plants from the plots of fair vigour by Fe levels. pH, texture (clay content), cation exchange capacity and organic carbon seem to be other soil properties with some degree of influence on plant performance. From these results, farmers are advised to increase soil aeration by implementing a drainage system and converting to a drip irrigation system, in addition to increasing soil pH by liming to reduce Mn toxicity.