Abstract

Boron (B) is an essential micronutrient in the growth of reproductive plant parts. Its deficiency and/or toxicity are widespread in arid and semi-arid soils with low clay contents. This study was planned to determine the response of sorghum (Sorghum bicolor L., non-leguminous crop) and cowpea (Vigna sinensis L., leguminous crop) to boron (0, 2, 4, and 16 mu g g(-1)) on four distinct soil series from Punjab, Pakistan i.e., Udic Haplustalf (Pindorian region), Typic Torrifluvent (Shahdra region), Halic Camborthid (Khurianwala region), and Udic Haplustalf (Gujranwala region). Overall, there was a significant difference (p 0.05) in yield between the sorghum (3.8 to 5.5 g pot(-1) of 5 kg dry soil) and cowpea (0.2 to 3.2 g pot(-1) of 5 kg dry soil) in response to B application. The highest yield was observed in both sorghum and cowpea either in control or at 2 mu g g(-1) B application in all four soils. Cowpea showed the same yield trend in all four soils (i.e., an increase in yield at 2 mu g g(-1) B application, followed by a significant decrease at the higher B levels). In contrast, sorghum exhibited greater variability of response on different soils; Udic Haplustalf (Pindorian region) produced the greatest yield at low levels of B application. However, Halic Camborthid produced its lowest yield at that level. Boron concentration in shoots increased with the levels of B application, particularly in sorghum. In cowpea, the plant growth was extremely retarded-and most of the plants died at higher levels of B application even if a lower concentration of B was measured within the shoot. Hot water-extractable B was the most available fraction for cowpea (R-2 = 0.96), whereas the easily exchangeable B was most available for sorghum (R-2 = 0.90). Overall, these results have implications for micronutrient uptake for both leguminous and non-leguminous crops.