Indexing of potassium, phosphorus and ca +mg in wheat grown on six benchmark soil series of northern India

In a nutrient indexing survey of wheat crop in the north-western Indo-Gangetic plains, foliage samples were collected at anthesis stage to study potassium, phosphorus, calcium and magnesium status in the leaf tissue. The analysis indicated a widespread potassium deficiency. Wheat crops growing on three of the six soil series, viz. Lukhi, Nabha and Bagru had 75, 47 and 42% samples moderately deficient in K, respectively, whereas in Khatki, Akbarpur and Rarha soil series from Uttar Pradesh, 23, 20 and 26% samples were found moderately deficient in K, respectively. Phosphorus was found to be sufficient in wheat plants growing on all the soil series, except Bagru. The Ca+Mg content ranged from 15.62 to 81.25 cmol(p⁺)kg⁻¹ leaf dry matter. On an average, sum of the macronutrient-cations (Ca+Mg+ K) in wheat foliage was found to be almost similar in all the soil series; ranging from 107 in Bagru to 114 cmol(p⁺)kg⁻¹ in Akbarpur. This indicates that wheat plants growing on these alluvial soils tend to maintain a constant cationic balance irrespective of their soil K fertility status. Though, a negative association between K concentration and that of Ca+Mg content was also observed which indicated that K has an antagonistic relationship with Ca+Mg in wheat.