Development of an organomineral fertiliser formulation that improves tomato growth and sustains arbuscular mycorrhizal colonisation.

Achieving sustainable agricultural development requires the efficient use of nutrient resources for crop production. Recovering nutrients from animal manures may play a key role in achieving this. Animal manures typically have low nutrient concentrations, and in ratios that are often not ideal for balanced crop nutrition. Here, combinations of organic and inorganic phosphorus (P) were formulated as granular products (organomineral fertilisers) with granule size suitable for transport and spreading. The fertilisers were produced by granulating powdered chicken litter with MAP and urea powders making the following formulations: 0:4, 1:3, 2:2, 3:1, 4:0. The kinetics of NH-N and P release from the fertilisers, and the effects on tomato growth and nutrition, as well as arbuscular mycorrhizal formation in roots following fertiliser application, were determined. Cumulative NH-N release ceased within 12 h, and was lower in the formulations with higher proportions of chicken litter. The cumulative P released reached approximately 80% of total P in all formulations, and the time to obtain maximum P dissolution was 19 days in the formulation that contained only chicken litter. The organomineral fertilisers increased tomato shoot growth by 15-28% compared to the chicken litter only, MAP only and MAP/urea formulations. Reasonable levels of mycorrhizal colonisation of tomato roots was achieved with the organomineral fertilisers. The results demonstrated that optimum plant growth does not depend solely on immediately available P, and that timing of nutrient supply to match plant demand is important. The combination of chicken litter with MAP sustained nutrient supply and improved plant growth. Taken together, organomineral fertiliser formulations are potential alternatives to inorganic P fertilisers that can improve crop growth and nutrition, while provide a sustainable use for animal production wastes.