Effective microorganisms inoculated with inorganic and organic fertilizers increase the growth, yield and quality of onion (Allium cepa L.)

Abstract

Effective microorganisms (EM) are increasingly used to stimulate the plant growth and nutrient cycling. Nevertheless, there is little information available about its co-application with chemical fertilizers and organic wastes to increase onion yield. In order to investigate the effects of EM inoculation with organic wastes and chemical fertilizers on soil fertility and onion growth, a two years’ pot experiment was carried out at Gomal University D.I. Khan, Pakistan. The experiment consisted of the following six treatments: control (T₀), 10 tons (t) ha^-1 farm yard manure (FYM) (T₁), 20 t ha^-1 pressmud (sugar filter cake) (T₂), 0.7 t ha^-1 compost (T₃), 5 t ha^-1 poultry manure (T₄) and mixed chemical fertilizer in the ratio of 100 : 40 : 56 kg ha^-1 as Nitrogen (N), Phosphorus (P) and Potassium (K) (T₅). Among these treatments, each treatment was applied alone and with EM. EM + pressmud mixture considerably enhanced the soil physical and chemical qualities as well as onion growth compared to other fertilizers with EM. Maximum potassium (K) and soil organic matter (OM) content were noted in the treatment where pressmud and EM were applied together. However higher Phosphorus (P) and Nitrogen (N) content were observed where poultry manure and compost were co-inoculated with EM, respectively. The application of EM with pressmud @ 20 t ha^-1 significantly enhanced onion growth by showing higher average onion plant height (64.88 cm), number of leaves plant^-1 (11.55), weight of bulb with leaves (102.70 g), weight of bulb without leaves (100.53 g) and weight of bulb (436.36 g pot^-1) relative to poultry manure, compost or FYM treatments. The same trend was detected during year II. These data proposed that pressmud applied with EM has the most potential to increase onion yield and quality. Our findings also point to the need for an integrated strategy that combines the application of organic fertilizer with easily accessible chemical fertilizer to reduce the possibility of reduced plant growth due to immobilization and the use of EM to improve the mineralization of organic nutrients. These recommendations call for further field testing.