Effects of use of high-quality composts on grain yield quality and nitrogen use efficiency of Pathum Thani 1 rice grown on Supphaya soil series

Abstract

Fertilizers and soil fertility management largely influence productivity, nutrient use efficiency and hence profitability of rice production systems. The use of agricultural and agro-industrial residues, such as filter cake and bagasse ash from the sugar industry, to produce high-quality composts is one of the most promising approaches to increase soil fertility while reducing environmental impacts. Therefore, an objective of this study was to investigate the effects of high-quality composts produced mainly from filter cake and bagasse ash on growth characteristics, yield and yield components, nitrogen use efficiency and economic returns over fertilizer cost of Pathum Thani 1 rice grown on Sapphaya soil series. A randomized block design with four replications was used. Treatments were four different fertilizer regimens: 1) no fertilizer use (control, C), 2) a use of high-quality composts (produced mainly from filter cake and bagasse ash) at a nitrogen rate of site-specific fertilizer management or at a rate of 8.0 – 13.6 – 12.9  kg N – P₂O₅ – K₂O /rai (CP_SSF), 3) a use of chemical fertilizers at an NPK rate of site-specific fertilizer management or a rate of 8.0 – 1.7 – 1.0 kg N – P₂O₅ – K₂O /rai (SSF) and 4) a use of commercial composts at a rate traditionally used by farmers or at a rate of 3.01 – 2.80 – 2.17 kg N – P₂O₅ – K₂O/rai (F). Results showed that the SSF rice had plant heights, tiller numbers, spikes/hill and grains/spike superior to (P<0.01) those from other treatments. In addition, the SSF rice had yield (868 kg/rai) that provided economic returns over fertilizer cost (6,020 Baht/rai), nitrogen use efficiency (42.39%) and agronomic nitrogen use efficiency (8.53%) higher than (P<0.01) those from other treatments. However, different fertilizer regimens had no effects (P>0.05) on amylose contents and elongation ratios of cooked rice. Interestingly, although the CP_SSF rice received total NPK nutrients equal to or greater than the SSF rice did, they may receive lower available nutrients than chemical fertilizers. Thus, it is important to quantify the available nutrient content of high-quality composts in order to modify the composts to contain optimally available nutrient contents for rice.