Salinity and boron effects on growth and yield of tepary and kidney beans

Crops tolerant to salt and boron have an advantage when grown in soils, near power plants, that are contaminated by saline cooling tower water or by waste products such as coal fly ash containing high levels of B. In addition, tolerant crops may have higher yields in and and semi and regions where salt and B problems coexist. This greenhouse study was conducted in order to compare the response of tepary bean (Phaseolus acutifolius A. Gray) and kidney bean (Phaseolus vulgaris L.) to combinations of high levels of solution B and chloride salts. The plants of both species were grown in 10-L plastic buckets containing silica sand and were irrigated with half-strength Hoagland's No. 1 nutrient solution to which boric acid and a mixture of NaCl and CaCl2.2H(2)O on a 1:1 equivalent ratio were added. Boron treatments consisted of 5, 20, and 25 mg.L-1 and the target electrical conductivity (EC) levels were 1, 4, 8, 12, and 15 dS.m(-1). The maximum growth and yield for tepary bean occurred at 5 mg.L-1 B and 4 dS.m(-1). These values of B and salinity were 6.5 and 4 times higher than those threshold values reported for kidney bean. Furthermore, tepary bean produced profitable yield (80% of control) in the 5 mg.L-1 B, 8 dS.m(-1) treatment and it even produced beans at B concentration as high as 20 mg.L-1 B, four times higher than that observed for kidney bean.