Is application of commercial potassium humates beneficial to soil and wheat?

Abstract

Commercial humates manufactured from oxidised lignites are often recommended to improve soil condition and crop growth. The benefits ascribed to these products are questioned, since they differ from humates that exist naturally in soils. Growth chamber, glasshouse and field experiments were conducted at facilities of the University of the Free State to quantify the influence of three potassium (K)-humate products on irrigated wheat growth and development, in loamy sand, sandy clay loam and clay loam soils. The humate products were applied to the soils at rates prescribed by their promoters. Results showed that the K humates were not beneficial for wheat growth and development as indicated by above-ground and subsoil plant parameters at tillering, stem elongation and maturity. However, the application of the K-humates caused higher bacteria and fungi counts in soil, which differed between the products applied. Despite the higher counts of bacteria and fungi in soil, grain yields were not affected, probably because no improvement in soil chemical properties were observed. Therefore, the application of K-humate products is not necessarily economically viable since they are relatively expensive. However, foliar applications of K humates may have stimulatory effects on wheat growth and development, resulting in better grain yields that could justify the higher production cost. An investigation into this aspect is suggested.

Keywords:

• growth stages
• loam soil
• organic matter
• oxidised lignite
• soil application
• soil humates