Response of Potassium Use Efficient Cassava Genotypes under Different Levels of N and K in an Ultisol of Kerala, India

Abstract

Among the different factors contributing to the production potential of a crop, the genetic potential of the crop in terms of nutrient acquisition, transport and utilization is important with respect to its nutrient use efficiency in reducing the external application of fertilizers. The research work conducted on screening K efficient cassava genotypes resulted in the identification of six genotypes viz., Aniyoor, W-19, 7 Sahya-2, 6-6, CR 43-8 and 7 III E3-5 based on their inherent physiological efficiency. These six genotypes were evaluated under different levels of K and N (0, 50, 100, 150 kg ha-1) to standardise the optimum dose of these nutrients for economic yield and also to confirm the N use efficiency potential of the K efficient genotypes. In this regard, observations were taken on nutrient use efficiency (NUE) parameters viz., HI, nutrient HI, nutrient uptake ratio, tuber yield and tuber quality. Since leaf and root architecture are the major contributors to NUE, LAI as well as the root parameters were also studied. Correlation among these different parameters were also studied especially to understand the effect of leaf and root characters on yield, NUE parameters including physiological efficiency. The study revealed significant differences among genotypes in the case of LAI and was higher under N than K levels. But, nutrient HI was higher under K. K levels significantly influenced the NUE parameters and K @ 50 kg ha-1 had highest impact on these parameters. Though no significant effect of K levels was seen on tuber yield, N @ 150 kg ha-1 resulted in significantly the highest tuber yield. The study of different root types in the root system of the crop under controlled conditions and in field over periodic growth intervals of cassava showed that, parameters viz., number of tuberous roots, its fresh weight and dry weights as well as root hairs were highest for the selected K efficient genotype Aniyoor. In the case of these genotypes under N levels, the identified genotypes viz., W-19 and CR 43-8 possessed larger volume of white roots, root length and diameter. Correlation studies revealed significant positive correlation of tuber yield with LAI, K/N uptake ratio and harvest index. Based on these parameters, the genotype Aniyoor and 7III E3-5 were identified as K efficient and the genotype W-19 and CR43-8 as N efficient.