Diagnosis of actual situation offield soil deterioration in arid regions and soil amendment by phytoremediation

从土壤盐分积累和作物营养失调的角度对墨西哥南下加利福尼亚州的土壤和作物的实际情况进行了调查。土壤盐分退化最严重的是科蒙杜地区，那里的农作物，特别是果树的生长受到盐分胁迫的抑制。因此，此后的研究主要集中在这一领域。柑橘和芒果出现营养失调，叶片出现盐害症状。叶片中钾、锰、锌的含量较低，钠的含量较高，反映了土壤条件，为农民提供了一种通过分析土壤数据进行土壤盐分累积风险判断的简便方法。对影响盐分积累的相关因素进行评分和总结。然后将总分乘以基于灌溉(方法和水量)的系数。该总分可以方便地用于盐分累积风险的判断。根据盐分对盐分的响应，提出了利用盐角、瑞士甜菜、高粱和甜菜等高耐盐性作物对盐分影响的土壤进行植物修复。结果表明，盐角草可用于碱化土壤的修复，其他3种植物可用于盐碱地的修复。胡椒是南下加利福尼亚州最重要的作物。因此，选择能在果实中转运较少的Na和积累较多的抗坏血酸的品种，对于维持水果的高产和品质具有重要意义。我们将利用这些结果来认识世界干旱地区土壤退化的实际情况，并通过植物修复来改善土壤养护状况。

The actual condition of soils and crops in the State of South Baja California, Mexico, was investigated from viewpoints of salt accumulation in soil and nutritional disorder of crops. The most severe soil deterioration by salts was found in Comondu area where growth of crops, especially of fruit crops, was suppressed by salt stress. The study, therefore, was concentrated in this area thereafter. Nutritional disorder was found in citrus and mango in which symptoms of salt injury were found in leaves. The content of K, Mn and Zn in leaves was low and that of Na was high, which obviously reflected soil condition.A simple method for risk judgment of salt accumulation in soil from analysis of soil data in Comondu area was presented for farmers. The factors related to salt accumulation were scored and summed up. The summed score was then multiplied by a coefficient based on irrigation (method and amount). The total score can be easily used for judgment of salt accumulation risk.Phytoremediation of salt-affected soil by highly salt tolerant crops such as Salicornia, Swiss chard, Kochia and beet, which are utilized for food and forage, was proposed from their response to salts. It was found that Salicornia could be utilized for remediation of sodic soil and other three species for saline soil.The difference between cultivars of peppers in response to salts was investigated. Pepper is the most important crop in the State of South Baja California. It is proposed that selection of cultivars that can translocate smaller amount of Na and accumulate more ascorbic acid in fruits is important in order to maintain high productivity and quality of fruits.We will develop these outcomes to recognize actual condition of soil deterioration in arid regions in the world and to amend conserve soil condition by phytoremediation.