Comparative effects of lignite-derived humic acids and FYM on soil properties and vegetable yield

The effects of a product containing lignite derived humic acids (Act) on medium and coarse textured soil properties and vegetable yield were verified through a 3-year pot experiment. This work sought to assess if a lignite derived humic acids product may substitute the use of manure considering its effects on soil properties and yields of vegetables. Both humic acids product in single (Actl) and double (Act2) doses as well as manure (FYM) were applied to soil. The plants tested were celery (Apium graveolens L. var. dulce (Mill.) Pers.) for the first two growing periods and leek (Allium ampeloprasum L,) for the last. The influence of Act application on soil properties together with the yield of tested plants was evaluated after each growing period. The results indicated that almost all soil parameters, such as sorption complex characteristics, organic matter quality and dehydrogenase activity, were improved after humic acids application in both soils. Act application also resulted in higher yields compared to others treatment. In the coarse textured soil the biomasses of roots and shoots were higher 3-fold and 4-fold, respectively after Act2 application than in the control, while in the medium textured this difference was about 2.5 fold for both shoots and roots biomasses. Organic carbon and C bound to humic acid contents remained significantly higher than in the control after the 3rd growing period while dehydrogenase activity and basis saturation significant increments were mainly visible after the 1st growing period. The soil quality index (SQI) was calculated and ranged within the treatments in the following ways: for the coarse textured soil, from 0.16 (control), 0.17 (NPK), 0.23 (FYM) to 0.25 (Acts) and 0.29 (Act2), while for medium textured soil, SQI, from 0.19 (control), 0,20 (NPK), 0,24 (FYM) to 0.25 (Actl) and 0.28 (Act2). However, the highest values were noted after a double dose of Act, and the stronger increments in soil properties occurred in the coarse textured soil versus the medium textured, demonstrating that the humic acids addition to the soil was especially effective in coarse textured, poor soils.