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

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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.