Effect of soil amendment with alfalfa pellets and glycerol on nutrition and growth of wheat

Abstract

Two pot experiments were carried out under controlled environment conditions in the laboratory. One was to assess the ability of alfalfa pellets to supply plant available N as an organic fertilizer. The other was to investigate the impact of applying glycerol on crop growth and soil characteristics. In the first experiment 4 different rates of two types of alfalfa pellets were tested by comparing with urea. In the glycerol addition experiment, four different rates of glycerol were tested. Wheat biomass yield, N and P uptake were measured in both experiments. Soil organic C, available N and P were also measured in the glycerol experiment. Results from the alfalfa pellet experiment showed that application of alfalfa pellets lead to a significant wheat biomass yield response and an increase in N and P uptake, even at the lowest application rates. Glycerol addition increased wheat yield biomass and N uptake at low and medium rates (100 and 1000 kg /ha) but resulted in reduced yield at the highest rate (10,000 kg/ha). The yield reductions at the highest rates were believed to be associated with N immobilization. In general, negative impacts on wheat growth were observed only at higher rates. Higher rates of glycerol added to the soil led to an increase in soil organic C concentration and a decrease in soil extractable nitrogen and phosphorus. Future experiments with glycerol addition will evaluate the effect of combination of glycerol with commercial fertilizer urea, and its effects on microbial respiration.