Development of a Biological Phosphate Fertilizer to Improve Wheat (Triticum Aestivum L.) Production in Mali

Abstract

Tilemsi Rock phosphate Tilemsi (TRP), is a good and inexpensive alternative to imported phosphate fertilizers. Thiobacillus thioparus, Thiobacillus thiooxidans and Thiobacillus ferooxidans, are known for their ability to oxidize soil sulfur and sulfides and influence the solubilization of inorganic phosphates. These bacteria have also a good potential to improve plant growth. In order to improve wheat response to fertilization with TRP, we describe in this work, the isolation from agricultural soils and the selection of different Thiobacillus strains with high TRP-solubilizing activities. Initially, 91 acidifying bacteria were selected, but after 10 subcultures on agar and in liquid media, only four bacteria were chosen for their strong P-solubilizing activities. No Thiobacillus ferrooxidans, was isolated from tested agricultural soils. A significant correlation was observed between acid production by isolated strains and phosphate solubilization. In a field trial in Koygour (Dire), wheat (Triticum aestivum cv. Tetra) was inoculated with selected strains of Thiobacillus and fertilized with the TRP or diammonium phosphate (DAP). The growth and yield parameters measured were the plant the tillers per plant, panicles per plant, percentage of fertile tillers (number of tillers with panicles/total number of tillers), panicle length, grain per panicle, grain yield calculated at 13% moisture, and 1000 grain weight. Yield increase relative to control and yield relative efficiency were also calculated. BioTRP1, with yield of 2840kg/ha grain, increased grains and straw yield at 45.64 and 73.81%, respectively with the highest relative yield efficiency. BioTRP1 is the only treatment not significantly different from the Di-ammonium phosphate. At harvest, average number of tillers was 18 for treatment 5 and a bit lower for di-ammonium phosphate with 17.8. Percentage of fertile tillers was 92% and 90% for the di-ammonium phosphate and the BioTRP1 treatments respectively. Panicle length was more than double for di-ammonium phosphate and BioTRP treatments compared to control. The number of grains/panicle was also highest for di-ammonium phosphate and BioTRP1 with 54 and 51 grains/panicle respectively. The di-ammonium phosphate, the BioTRP1 and control were significantly different and showed the maximums and minimum weights of 28; 27 and 20g for 1000 grains of wheat. BioTRP2 and BioTRP3, formulated with Thiobacillus thiooxidans AHB411 and Thiobacillus thiooxidans AHB417, also caused yield increases of 33.33 and 11.97% respectively. The choice of Thiobacillus thiooxidans AHB 436, and the formulation of BioPNT will be discussed