EFFECT OF SOIL AMENDMENT WITH ALFALFA POWDERS AND DISTILLERS GRAINS ON NUTRITION AND GROWTH OF CANOLA

Abstract

Two pot experiments were carried out under controlled environment conditions in the growth chamber to assess the potential use of alfalfa powders and distiller grains as organic fertilizers. Two types of dehydrated alfalfa powders (one with canola meal protein extraction by-product and one without) and two types of distiller grains (dried distillers grain with distillation solubles added and wet distillers grain without solubles) from wheat-based ethanol production were evaluated. Four different nitrogen (N)-based amendment application rates (0, 100, 200 and 400 kg N ha−1) were used along with urea applications made at the same N rates to a Brown Chernozem (Aridic Haploboroll) loamy textured soil collected from south-central Saskatchewan, Canada. Canola biomass yield, N, phosphorus (P), potassium (K), zinc (Zn), and cadmium (Cd) uptake were measured along with soil properties including pH, salinity, organic carbon, total nitrogen, phosphorus and extractable nutrients and cadmium before and after canola growth in each of the treatments. Application of alfalfa powder and distiller grain amendments resulted in significant canola biomass yield increases along with increased N, P, and K uptake compared to the unfertilized control. However, only a portion of the N added (∼30% to 50%) in the organic amendments was rendered available over the five week duration of the experiments. Amendments that had higher N content and lower carbon (C):N ratios such as dried distillers grain with solubles resulted in greater canola N uptake. Reduced germination and emergence of canola seedlings was observed at high rates of addition of distillers grain (400 kg N ha−1), the reason for which is unclear but may be due to a localized salt or toxicity effect of the amendment. The amendment with alfalfa powders and distiller grains resulted in small increases in residual soil nutrients. Effects on pH, salinity, organic carbon and extractable metals tended to be small and often not significant. Alfalfa powders and distillers grains appear to be quite effective in supplying nutrients, especially N, for plant growth over the short-term.