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.

中文翻译：

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土壤和植物分析以诊断啤酒花田不规则生长

在耕地中，通常会出现一片片发育不良的植被，而没有明确指示影响植物生长的因素。本研究的目的是调查葡萄牙东北部啤酒花 (Humulus lupulus L.) 田中这些不规则现象背后的原因，这些现象大大降低了作物产量和农民的利润，并为农民提供了适当补救措施的指导。在啤酒花田中选择不同植物发育水平的斑块，并根据植物活力（弱、一般和良好）进行分类。确定了几种土壤特性，这些特性与植物不同部分（啤酒花、叶子、茎）的植物营养状况和干物质产量有关。数据进行方差分析和主成分分析。结果表明，作物产量减少的主要原因是土壤通气不良以及土壤和组织中锰和铁含量过高。来自较弱活力地块的植物似乎特别受有毒浓度的锰的影响，而来自中等活力地块的植物受铁含量的影响。pH、质地（粘土含量）、阳离子交换能力和有机碳似乎是对植物性能有一定影响的其他土壤特性。根据这些结果，建议农民通过实施排水系统并转换为滴灌系统来增加土壤通气，此外还可以通过撒石灰来提高土壤 pH 值以降低锰毒性。来自较弱活力地块的植物似乎特别受有毒浓度的锰的影响，而来自中等活力地块的植物受铁含量的影响。pH、质地（粘土含量）、阳离子交换能力和有机碳似乎是对植物性能有一定影响的其他土壤特性。根据这些结果，建议农民通过实施排水系统并转换为滴灌系统来增加土壤通气，此外还可以通过撒石灰来提高土壤 pH 值以降低锰毒性。来自较弱活力地块的植物似乎特别受有毒浓度的锰的影响，而来自中等活力地块的植物受铁含量的影响。pH、质地（粘土含量）、阳离子交换能力和有机碳似乎是对植物性能有一定影响的其他土壤特性。根据这些结果，建议农民通过实施排水系统并转换为滴灌系统来增加土壤通气，此外还可以通过撒石灰来提高土壤 pH 值以降低锰毒性。