Phenolic allelochemicals released by Chenopodium murale affect the growth, nodulation and macromolecule content in chickpea and pea

The present study was conducted to investigate the effect of the residue of Chenopodium murale L. on growth, nodulation and macromolecule content of two legume crops, viz., Cicer arietinum L. (chickpea) and Pisum sativum L. (pea). A significant reduction in root and shoot length as well as dry matter accumulation occurred when both the legumes were grown in the soil amended with 5, 10, 20 and 40 g residue kg(-1) soil. In general, a gradual decline in growth was associated with an increasing amount of residues in the soil. There was also a significant reduction in total chlorophyll content and the amounts of protein and carbohydrates (macromolecules) in plants growing in the residue-amended soil. The nodulation was completely absent in chickpea and pea when the plants were grown in the soil amended with 10 and 20 g residue kg(-1) soil, respectively. At a lower rate of residue amendment (5 g kg(-1) stop soil), a significant decline in nodule number and weight, and leghaemoglobin content was recorded. Root oxidizability, an indirect measure of tissue viability and cellular respiration, was adversely affected in both the legumes under various treatments of residue amendment. The observed growth reduction concomitant with increased proline accumulation indicated the presence of some inhibitory compounds in the residue-amended soil. It was rich in phenolics identified as protocatechuic, ferulic, p-coumaric and syringic acid with 12.8, 30.4, 20.2 and 33.6% relative content, respectively. The results suggest that the residue of C. murale releases phenolic allelochemicals, which deleteriously affect the growth, nodulation and macromolecule content of chickpea and pea.