Sulphur-zinc interaction in integrated nutrient supply system of wetland rice ( Oryza sativa L.)

Abstract

An experiment was conducted at Cropping Systems Research Centre (CSRC), Karamana, Thiruvananthapuram during rabi season of 2005-06 to study the response of wetland rice to sulphur and zinc under integrated nutrient condition using the variety Aiswarya. The experiment was laid out in factorial randomized block design with three replications. The treatments consist of combinations of two levels of nitrogen (N), three levels of sulphur (S) and two levels of ZnSO4 (Z) along with two controls (zero level of fertilizer treatment and Package of Practice recommendation treatment). Recommended dose of nitrogen applied as 100 per cent inorganic (N1) and 50 per cent N applied equally as organic-inorganic integration (N2) constitutes the N levels. Sulphur applied @ 10 kg ha-1 (S1), 20 kg ha-1 (S2) and 30 kg ha-1 (S3) were the three sulphur levels. The two ZnSO4 fertilizer levels are10 kg ZnSO4 ha-1 (Z1) and 20 kg ZnSO4 ha-1 (Z2) and farmyard manure @ 5 t ha-1 was applied uniformly to all treatments. Results of the experiment revealed that the main effects of nitrogen, sulphur and ZnSO4 as well as their combinations exerted positive significant influence on the growth and yield attributing characters of rice. Organic- inorganic integration (N1) significantly influenced growth characters like plant height, tiller number hill-1, leaf area index and dry matter production and yield character like number of panicles hill-1 and yield while higher sulphur (S3) level upto 30 kg ha-1 were found significantly superior in influencing all growth, yield attributing characters and yield of rice to lower level (S1). ZnSO4 @ 20 kg ha-1 (Z1) recorded significantly higher plant height, tiller number hill-1 leaf area index, number of panicles hill-1, weight of panicle, filled grains panicle-1 and yield of rice. Treatment combinations also significantly influenced most of the growth, yield attributing characters and yield of rice compared to controls. Chlorophyll content was significantly influenced by S application only. Nutrient uptake was also influenced by treatments and their combinations. Organic- inorganic integration (N1) significantly favoured the uptake of N, P, K, S and Zn while S application at higher levels contributed significantly to uptake of N, S and Zn. Uptake of N, S and Zn was significantly influenced with higher level of ZnSO4 @ 20 kg ha-1 (Z2). Combination of S @ 30 kg ha-1 along with ZnSO4 @ 20 kg ha-1 produced highest uptake of Zn. Available N and K exhibited significant variation with combined use of both organic and inorganic source of nitrogen. Available nutrient status of N, K, S and Zn was significantly increased by S application at higher levels. Again, there was increase in availability of S and Zn content of the soil with higher level of ZnSO4 (20 kg ha-1) application. N X S and S X Zn interactions also played significant role in increasing available N and S content of soil. Treatment combinations recorded significantly better results in uptake and availability of nutrients compared to control treatments. Highest benefit cost ratio was recorded by a combination of S @ 30 kg ha-1 + ZnSO4 @ 20 kg ha-1 along with full recommended dose of N as inorganic fertilizer.