Productivity and Plasticity of Wheat and Cynodon dactylon (L.) Pers. in Pure and Mixed Stands

The interference between wheat and Cynodon dactylon was studied by growing the two species in pure and mixed stands. Both the species responded to increasing density by extreme plasticity and there was no density-induced mortality. The plasticity in wheat extended to seed weight, which is often considered to be a rigid character. The replacement series as done here for mixed cultures did not bring out clearly interference between species with divergent plant size and growth habit. It was found that interference between two species under such situations could best be studied by varying proportion as well as total density in the mixture. Increase in density of one species in the mixture adversely affected the growth yield of the other one. Though wheat had a greater influence on the growth of C. dactylon, compared to the reverse situation, it is important to note that the dry weight yield and seed production of wheat also decreased significantly with increase in density of C. dactylon in the mixture. This tendency was noticeable to a lesser degree in the case of seed weight of wheat. Further, nutrient content in the shoot also varied significantly in both species depending on the degree of intra- and interspecific competition. Where one species had an initial advantage of time over the other, the one introduced later into the mixture suffered much more than when the two species were introduced simultaneously.