The role of humic substances to improve degraded soils for increasing crops production

One of the main problems of lowering crops production on degraded soils is the low soil organic matter. Application of humic substances may improve the quality of degraded soils. The objectives of this research were to study the effect of humic substances application on the production of rice, water spinach, sweet potato, and oil palm, and to describe the mechanism of increasing crops production due to the application of humic substances. In this study, the humic substances were extracted from soft brown coal using a strong base KOH. Humic substances in difference doses are applied to various soil types for several crops. The results showed that application of humic substances increased the production of rice, water spinach, sweet potato, and oil palm. The highest production increase is obtained with a dose of 10-15 liters of the humic substance/ha with a carrier zeolite of 10-20 kg/liter of humic substances. The application of humic substances to soils increases the nutrients available in the soils as well as the the growth of plant roots so that plants can absorb more nutrients from the soils.