Agrobiological Characteristics Research Articles

Evaluation of parameters related to chemical and agrobiological qualities of wheat-straw composts including different additives

The chemical and agrobiological characteristics of 37 composts from wheat straw with different additives were evaluated through routine tests. In general, the plant yield under greenhouse conditions in soils amended with these composts was unrelated to data from the phytotoxicity germination biotest, but with the chemical parameters reflecting selective biopolymer degradation in straw. This suggests that factors such as microbial immobilization of nutrients had greater influence than phytotoxic inhibitor compounds in the plant yield of the soils amended with the composts studied. Monitoring the composition of the water-soluble fraction was also useful as regards crop yield of soils improved with compost. The factors potentially connected with the positive or depressive effect of composts in soil were assessed through factorial design experiments involving successive harvesting, calcium carbonates and mineral fertilization. In general, mineral fertilization may lead to decreased yields in soils to which immature composts are applied. The effects on compost maturity of the different by-products used as additives are discussed for the system studied.

Effects of different chemical modifications on peat humic acid and their bearing on some agrobiological characteristics of soils

Abstract Twelve preparations from peat humic acid were obtained through laboratory treatments modifying its structural parameters, oxygen (O)‐containing functional groups and nitrogen (N) content. The treatments included acetylation, amidation, ammonia fixation, methylation, nitration, oximation, sulphonation, and selective degradations. The transformed humic products were characterized by routine laboratory analyses. Then, plant yield and different properties of two soils treated with the corresponding potassium (K)‐humates were determined in greenhouse experiments. The main effects and interactions between parameters affecting the response of soil and plant to humic acid application were analyzed through factorial designs. Whereas the application rate (2 to 4 Mg/ha) had no great bearing on plant yield (accounting for between 84 to 176% of the untreated soils), the opposite occurred with aggregate stability and cation exchange capacity. Among the parameters examined in the humic acids, the hydrogen/carbo...