Effect of potassium humate on soil properties and growth of wheat

[摘要] English: Soil properties (biological and chemical) and crop response are dependent on the inherent soil organic matter content. Since South African soils are naturally low in organic matter content commercial humates serve as attractive soil amendments in improving soil quality. This is the result of commercialisation giving the impression that humates have biological and chemical properties similar to those in soil humus. In an attempt to substantiate these claims three separate experiments were conducted at the University of the Free State to examine the effect of K-humate on soil properties and wheat response during the 2006 growing season. The biological (bacterial and fungal count) response was evaluated in growth chambers by applying three different K-humate products at rates of 0, 3 and 5 L ha-1 in a band on a red loamy sand topsoil. Soil cores were sampled on a weekly basis for six weeks and microscopically analysed. Bacterial and fungal count differed significantly as a result of the product by application rate interaction but no consistency was found. Over time both the bacterial and fungal activity increased rapidly for week 2 and 3 but decreased at week 3 for the bacteria. Both the organisms' reactions stabilised from week 3 to 6. The chemical soil properties were also tested in growth chambers but only K-humate (single product) was applied as a coating on granular 2:3:2 (22) fertiliser at 0 and 3 L ha-1 in a band 50 mm below the soil surface. The chemical soil properties showed no response after 5 months to the application of K-humate. A glasshouse experiment was also conducted to evaluate the growth and yield response of wheat on three textural class topsoil's (8, 22 and 37% clay) and four K-humate applications (0 L ha-1, 3 L ha-1 single application, and 3 and 6 L ha-1 split application �?50% at planting and 50% at tillering). K-humate as a coating on 2:3:2 (22) granular fertiliser was banded and Greensulph (27) topdressed at the required fertiliser rate for a yield potential of 8 t ha-1. Plant growth parameters were analysed at tillering, stem elongation and maturity, both above- and below-ground. Virtually no significant influences were found with the K-humate application rate and soil texture interaction on the measured parameters. Notwithstanding this, positive effects were noticed and a split application whereof half of the K-humate was applied at planting and the other half at tillering showed the best results. A field experiment was also conducted to examine K-humates influence on wheat growth and yield. Two experiments was conducted, one under full irrigation (700 mm) with a yield potential of 8 t ha-1 and the other supplementary irrigation (350 mm) with a yield potential of 4 t ha-1. K-humate was applied as a coating on granular 2:3:2 (22) fertiliser and bandplaced either as a single application (0, 1.5, 3, 5 and 6 L ha-1) or a split application (5 and 6 L ha-1) 50% at planting and 50% (K-humate as a coating on Greensulph (27)) at tillering. Irrigation was applied using a line source irrigation system. The field experiment confirmed the results obtained in the glasshouse with virtually no significant effects as a result of the applied K-humate on the measured plant parameters.

[发布机构] University of the Free State