Boron and lime effects on yield and deficiency symptoms of rice grown in greenhouse on acid Typic Glossaqualf

No boron (B) deficiencies have been reported for rice (Oryza sativa L.) grown in the United States and, when occurring elsewhere, reports often lack details of deficiency symptoms and leaf-B critical values. An experiment was conducted to determine the effect of B and lime on yield, pollen viability, and to determine diagnostic symptoms of B deficiency in rice. Rice cv. "Bengal" was grown in the greenhouse on a soil acquired from a rice farm from SW Louisiana in the United States, a Caddo silt loam (Caddo sl) (Typic Glossaqualf, fine-silty, siliceous, thermic), treated with 0.44 mg B kg(-1) (+B) or no B (-B). Split plots were limed at rates of (i) none; (ii) 224 mg kg(-1) CaO + 40.3 mg kg(-1) MgO; and (iii) 673 mg kg(-1) CaO + 121 mg kg(-1) MgO. Rice was also grown in -B and +B potting media and in -B sand culture using nutrient solution identical to that used in other studies of ours. Rough-rice yields from the +B Caddo sl treatment was 11% higher than from the -B treatment (29.3 vs. 26.3 g pot(-1); P=0.02). The yield increase was likely due to fewer damaged pollen (8%) found from the +B than the -B treatment (17%; P=0.014). Leaf-B at tillering was 11.3 mg kg(-1) for the B-treated rice and 7.1 mg kg(-1) from the -B treatment. Liming did not significantly affect leaf B or yields. Boron deficiency symptoms were found only in the -B sand-culture where yields were 1.1 gpot(-1), 96% less than that from the +B Caddo sl. Symptoms were like those found in our earlier hydroponic studies with twisted and whitish leaf tips starting at tillering and 1-cm white bands across the width of leaves. Maturity was delayed about four weeks. Boron deficiency from the Caddo sl and sand treatments occurred with leaf B less than or equal to 7 mg kg(-1) and with a Caddo sl soil B of 0.18 mg hws (hot-water soluble) B kg(-1). Given that no B deficiency symptoms were found in rice experiencing moderate yield loss grown on the rice soil, one must rely on soil and plant analyses to help detect likely candidates for moderate B deficiency.