Feasibility of Rock Phosphate and Other Amendments in Preventing P Deficiency in Barley on a P-Deficient Soil in Northeastern Saskatchewan

In the Canadian Prairies, many soils on organic farms are low in available P, and the only alternative is to use external sources to prevent P nutrient deficiency on these soils. A 3-year (2012 to 2014) field experiment was established in spring 2012 on a P-deficient soil near Kelvington, Saskatchewan, Canada, to determine the potential of organic amendments (alfalfa pellets, compost manure, thin stillage and distiller grain dry of wheat), inorganic amendments (rock phosphate granular, rock phosphate fine, wood ash and bone meal ash) and microbial inoculants/products (JumpStart® and MYKE®PRO), applied alone or in a combination with N and/or P commercial fertilizers, in preventing P deficiency and increasing seed yield, N and P uptake of barley. Compared to unfertilized control, N only treatment did not result in any significant increase in seed yield, while application of P alone increased seed yield significantly but to a lesser degree than when both N and P fertilizers were applied together in all 3 years. Rock phosphate did not result in any seed yield benefit, even when applied along with N fertilizer. Wood ash fine increased seed yield of barley significantly only in the presence of N fertilizer, with highest seed yield in the presence of both N + P fertilizers. Seed yield of barley increased moderately with alfalfa pellets, significantly with compost manure, and considerably with distiller grain dry of wheat, but highest seed yield was obtained from thin stillage, which was essentially similar to that obtained from the N + P fertilizer combination. There was no yield benefit from JumpStart or MykePro in any year and only slight benefit from bone meal ash in 2013. The addition of N fertilizer to MykePro or bone meal ash treatments increased seed yield, but highest yield was obtained when both N and P fertilizers were added, suggesting a lack of available P for optimum seed yield. With few exceptions, the response trends of total N and P uptake in seed + straw to the amendments studied were generally similar to those of seed yield. In conclusion, the organic amendment “thin stillage” provided balanced nutrition and produced yield and nutrient uptake of barley similar to balanced N + P fertilizer treatment, and it was closely followed by “distiller grain dry of wheat”, with moderate benefit from compost manure and some benefit from alfalfa pellets. In this extremely P-deficient soil, rock phosphate was not found effective in preventing P deficiency in barley, while wood ash and bone meal ash provided moderate increase in barley yield, with little yield benefit from JumpStart and MykePro, when other nutrients were not limiting in the soil.