Responses of Cowpeas to Applications of P and Fe in Calcareous Soils1

Abstract

AbstractThe relationship between P and Fe in nutrition and development of plants have been studied in detail for some crop species. However, there is no such report available on cowpeas (Vigna sinensis L.). This study was initiated to investigate the effects of P and Fe on growth and mineral contents of cowpeas in two arid region soils.Cowpeas were grown for 8 weeks in two soil types (Typic Xerofluvent and Xerollic Xerochrept) from two locations (Airport and Kooshkak, respectively) containing various levels of P (0, 50, 100, and 200 ppm) and Fe (0, 5, 10, and 20 ppm). Airport soil (loam) had high soluble salts, high exchangeable Na and low organic matter, N, Fe, Zn, and Mn as compared to Kooshkak soil (silty clay).Symptoms of Fe deficiency developed only on plants growing in the Airport soil when no Fe was applied. With the application of Fe as little as 5 ppm, the symptoms were prevented. The dry matter yield of plants grown in the Airport soil was significantly lower than that grown in Kooshkak soil under all treatments. Best plant growth was obtained when 50 or 100 ppm P were added to each soil; however, no Fe was required in the Kooshkak soil while 20 ppm Fe were needed in Airport soil for optimum growth.The mineral contents in the tops of plants grown in either soil type were affected differently with increased levels of applied P or Fe. Significant interactions were observed between P and Fe treatments for most of the characteristics measured.