Fertiliser Response of Cassava Cultivars as Measured by Leaf Colour, Chlorophyll Content, Nitrate Reductase Activity and Tuberous Root Yield

摘要

Response of cassava (Manihot esculenta Crantz) cutivars to applied NPK was studied on the Ultisols of the Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram. Parameters evaluated included LCC scores, SPAD values, chlorophyll contents (Chl a, Chl b and Chl a+b), nitrate reductase activity and tuberous root yield. The experiment was laid out in a split-plot design with three NPK rates (control - 0 NPK, 100% NPK and 150% NPK) in the main plots and four cultivars of cassava, namely H-165, H-226, Sree Jaya and M-4 in subplots in the subplots..Each treatment was replicated thrice. Site-specific nutrient management approach using the modified Quantitative Evaluation of Fertility of Tropical Soils (QUEFTS) model was used for computing the 100% NPK and 150%.NPK rates. These have subsequently been referred to as the 100% SSNM-NPK and 150% SSNM-NPK, respectively.. The study revealed on par results between 100% SSNM-NPN and 150% SSNM-NPN treatments on LCC scores, SPAD values, chlorophyll contents, nitrate reductase activity and tuberous root yield. The cassava cultivars significantly varied among themselves in influencing the leaf colour, chlorophyll content and tuberous root yields. The cultivars H-165 (25.52 t ha~(-1)) and H-226 (25.19 t ha~(-1)) produced significantly high tuberous root yield compared to Sree Jaya (20.86 t ha~(-1)) and M-4 (18.12 t ha~(-1)).