Integrated nutrient management for short duration cassava in lowlands

Abstract

An investigation entitled "Integrated nutrient management for short duration cassava in lowlands" was undertaken in the Instructional Farm, College of Agriculture, Vellayani from September 2002 to April 2003 to develop an integrated nutrient schedule for short duration cassava in lowlands and to work out the economics of cultivation. The treatments consisted of factorial combinations of two varieties of cassava (Sree Vijaya and Kariyilapothiyan), three sources of organic manure (farmyard manure, poultry manure and coir pith compost) and three levels of nitrogen (50, 75 and 100 kg N ha-I). The trial was laid out in 32 x 2 asymmetrical confounded factorial design with two replications confounding VMN in replication J and MN in replication II. A uniform dose of 50 kg P20S ha' and 100 kg K20 ha-' was applied to all the plots. In general, the local var. Kariyilapothiyan recorded superior values of growth characters like plant height, leaf number and leaf area index. Among organic manures, farmyard manure produced higher values of growth characters. But total dry matter production was not influenced either by varieties or by sources of organic manure. Levels of N had profound influence on growth characters and 75 kg N ha-' was found superior in the case of both varieties. Varieties exhibited no variation in yield components except length of tuber. The improved var. Sree Vijaya produced longer tubers than the local variety. The yield components except tuber weight per plant did not vary with the source of organic manure. Poultry manure recorded the highest value of tuber weight per plant. Nitrogen @ 75 kg N ha" recorded higher values of yield components.

The performance of both varieties In terms of tuber yield, top yield and utilization index was found similar. Among organic manures, the highest tuber yield was recorded by poultry manure which was on par with farmyard manure but superior to coir pith compost. At the same time the effect of farmyard manure was on par with coir pith compost. The top yield was not influenced by the source of organic manure but utilization index exhibited the same trend as that of tuber yield. The tuber yield increased when N level was increased from 50 to 75 kg N ha-I but decreased with further increase in the level of nitrogen. Top yield increased with increase in the level of nitrogen. Application of75 kg N ha" registered the highest utilization index. Neither varieties nor sources of organic manure recorded any significant variation in starch content of the tuber. But the local variety recorded higher protein content and lower HeN content than the improved variety. Poultry manure treated plants registered the highest protein content and the lowest HeN content. Application of 75 kg N ha" was sufficient for obtaining higher starch and protein contents. The HeN content increased with increase in the level of nitrogen though it was within permissible limits. The improved var. Sree Vijaya obtained higher scores for taste than the local variety. The taste of the tuber was not affected by the source of organic manure. Maximum score for taste was recorded by 75 kg N ha'. The cooking quality of the tuber of both varieties was judged as good. Uptake of Nand K was not influenced by varieties. But in the case of P uptake, the var. Sree Vijaya recorded higher P uptake than the local variety. Nutrient uptake did not vary with the source of organic manure. Maximum uptake of nutrients was observed when 75 kg N ha-I was applied. Significant variation In available Nand K status of the soil after the experiment was observed only due to source of organic manure. Farmyard manure applied plots showed higher status of these nutrients compared to poultry manure and coir pith compost applied plots. Higher status of available P was observed in the soil when the improved variety was raised irrespective of the source of organic manure. Nitrogen @ 75 kg N ha-I registered higher available P content in the soil after the experiment. The study revealed that application of farmyard manure @ 12.5 t ha" or poultry manure @ 5 t ha" along with 75:50:100 kg NPK ha" resulted in higher returns from Sree Vijaya and Kariyilapothiyan, two short duration varieties of cassava, in lowlands. No variation between varieties was observed in their response to N levels as well as to the sources of organic manure. The results suggested the suitability of poultry manure as an alternative to farmyard manure for cassava cultivation in lowlands. Coir pith compost can also be used as an alternate source of organic manure provided it is made cost effective.