Utilization of Effluent from Biogas Production as Nitrogen Source for Pak-choy (Brassica campestris var chinensis) Grown on Kamphaeng Saen soil

Abstract

In field trials, effluent from biogas production (EFB) of liquid swine wastes was tested as nitrogen source and as irrigation water for Pak-choy (Brassica campestris var chinensis) grown on Kamphaeng Saen soil. The EFB was applied weekly at 40,000 l/rai (6.25 rai = 1 ha) throughout the growing period. With the designated rate, the total nitrogen content of the EFB was equivalent to 20 kgN/rai (125 kgN/ha). Inorganic fertilizer (IF) in the form of ammonium sulfate at the same rate of N as above was used as the standard treatment. Combinations of halves of the two treatments (1/2EFB+1/2IF) and half of the rate of the EFB irrigation water (1/2EFB+IRR) were set up as the alternative treatment. Consecutively, the field trials were conducted 5 crops in the dry seasons. The results indicated that the crop yield from the EFB plot was equivalent to 85% of that from the IF plot whereas the 1/2EFB+1/2IF could produce crop yield comparable to that produced by the IF. Half of the EFB rate in combination with irrigation water supplied less nitrogen to the crop resulting in low crop yield and low nitrogen content in the plant tissue. In addition, the EFB could be used as an alternative source of water for plant growth. It could substitute the irrigation water as much as 40,000 1/rai/wk (250,000 1/ha/wk) or 280,000 1/rai (1,750,000 1/ha) for the whole growing period. With the mentioned rate, there was no change in some chemical and physical properties of the soil such as pH, electrical conductivity, the contents of P, K, Ca, mg, Cu and Zn, bulk density, available moisture capacity and aggregate size distribution.