Wheat (Triticum aestivum L.) response to boron in contrasting soil acidity conditions

Abstract

Wheat cultivation in acid soils may be simultaneously limited by metal toxicity, deficiency or Ca and Mg imbalance, and B deficiency. The aim of the present study is to assess whether the wheat response to B increases, as the crop condition in the acid soil becomes more stressful. The study was conducted in a greenhouse, and an Oxisol sample was used as the substrate. It assessed the interaction between three soil acidity treatments (low [pH-CaCl2 5.6], very high [pH-CaCl2 4.2] and very high acidity with gypsum [pH-CaCl2 4.3]) and five B treatments (0, 0.15, 0.40; 1.25 and 3.50 mg dm-3). The very high addition of gypsum into a very acid soil caused a nutritional imbalance in wheat (mainly to Mg) and led to lower dry matter accumulation values, a condition in which B presented stress alleviation. Such condition resulted in significant changes in root growth, transpiration and the availability of Mg and Ca/Mg ratio in the rhizosphere soil. The concentration of K, Ca, Mg, P, Fe, Mn, Zn, Cu and Al was little affected by B, since the K:Mg ratio was more important. The treatment with very high acidity, with gypsum, also showed higher B toxicity. Thus, wheat has shown higher B response in acid soil under the most stressful condition.