MSc

Cassava (Manihot esculenta Crantz), popularly known as tapioca, is one of the world’s most important staple food crops. It ranks sixth among the major contributors of food in the world. It has been a major contributor of food, nutrition and income especially for the poor. Its biological efficiency and multi use characteristics warrant for crop management strategies to exploit its production potential to the maximum. Due to the high cost of labour and lack of timely availability of labour, the farmers show interest to introduce cassava as a substitute for rice in his crop cafeteria. “Vellayani Hraswa” is a short duration variety of cassava released by the Kerala Agricultural University recently. Branching habit and short duration nature coupled with greater production potential make this variety physiologically unique and outstanding compared to other cassava varieties ever released. These characters warrant for separate package in nutrient management. Keeping these views in mind, an experiment entitled “Fertilizer scheduling for short duration cassava variety “Vellayani Hraswa” was conducted with the objective of studying the influence of NPK fertilizers on the performance of short duration cassava variety “Vellayani Hraswa” and to arrive at a fertilizer recommendation for the same. The experiment was laid out at the Instructional Farm, College of Agriculture, Vellayani during the period from 25th June to 25th December 2003 in a 33 Factorial Randomized Block Design (FRBD) with two replications and three factors (NPK) each with three levels (50,75 and 100 kg ha-1). The crop was raised adopting the agronomic practices for cassava outlined in the Package of Practices Recommendation: Crops of Kerala Agricultural University KAU (2002). The results of the experiment are summarized as follows.
There was no significant difference on the plant height at all the growth stages of the plant due to the treatments. However, there was an increasing trend on the height of the plant as the dose of nitrogen increased. Higher dose of nitrogen increased the number of leaves produced in cassava at all the growth stages. At harvest stage, the plants retained maximum number of leaves for all the treatments which indicates that the leaf fall is minimum, a peculiar characteristic of the variety.
Tuber production was influenced significantly by all the treatments. Application of 100 kg K ha-1 resulted maximum tuber yield. NPK @ 50: 50: 100 kg ha-1 produced maximum tuber yield (47.09 t ha-1). This variety favours a 1:1:3 NPK ratio for higher tuber production. Length of tubers was not influenced by different levels of N, P and K. However, NPK @ 75:50:75 kg ha-1 produced tubers with maximum length in cassava.
Girth of tubers was significantly increased due to the application of nitrogen alone @ 100 kg ha-1 in cassava. Application of NPK @ 75:100:100 kg ha-1 produced the highest quantity of dry matter. No significant influence on LAI due to the application of N, P and K fertilizers was observed. Stomatal conductance in cassava leaves was maximum due the application of P and K @ 75 kg ha-1 (p2k2) with significant effect.
Chlorophyll content of cassava leaves was not influenced significantly due to different levels of N, P, K application. The highest dose of NPK (n3p3k3) recorded highest chlorophyll content.
Phosphorus has influenced significantly on tuber starch content. An increasing trend due to incremental doses of K up to 100 kg ha-1 was also observed. Treatment n3p3k3 (100:100:100 kg ha-1) recorded the highest starch content in tubers.
Crude protein content was significantly influenced by the nutrients NPK. Application of N @ 100 kg ha-1 registered the highest protein content. NPK @ 100:100:75 kg ha-1 produced tubers with maximum protein content.
Hydrocyanic acid content was mainly affected by higher doses of nitrogen. Nitrogen alone @ 100 kg ha-1 produced maximum HCN content in the tuber. But there was significant decline in HCN content as the dose of K increased. When the treatment n3p3k1 (100:100:50 kg ha-1) produced tubers with the highest HCN content, the treatment n1p2k3 produced tubers with lowest HCN content.
Cooking quality of tubers was significantly influenced by potash. Maximum cooking quality could be obtained when K was increased to 75 kg ha-1. In general, the uptake of N, P and K by plants was maximum for the highest doses of N, P, K. A fertilizer dose of N, P, K @ 50:50:100 kg ha-1 produced maximum tuber yield (47.09 t ha-1) with moderate cooking quality of tubers. The moderate fertilizer cost resulted high BC ratio of 3.32 for the treatment n1p1k3, the best dose arrived at and to be recommended for the short duration cassava variety “Vellayani Hraswa”.
It has to be concluded that the cassava variety “Vellayani Hraswa” is most economical due to its short duration (about 6 months), high yield (45-50 t ha-1) good cooking quality (1.5) and moderate fertilizer requirement (50:50:100 NPK ha-1).