Intraspecific Competition and Population Regulation in Phalaris minor Under Different Nitrogen Fertilization Levels in Wheat

Abstract

Phalaris minor is one of the most problematic grassy weeds in wheat-based cropping systems, often exhibiting strong competitive ability and rapid population buildup under favorable agronomic conditions. The present study investigated intraspecific competition and population regulation of P. minor under different nitrogen fertilization levels in wheat fields. Field experiments were conducted using varying nitrogen doses to evaluate weed density, biomass accumulation, tiller production, seed output, and wheat yield response under natural infestation conditions. The results indicated that nitrogen fertilization significantly influenced the growth and competitive dynamics of P. minor populations. Higher nitrogen levels enhanced both wheat and weed growth, however, P. minor showed a strong competitive response, resulting in increased biomass production and higher seed output under elevated nitrogen conditions. Intraspecific competition among P. minor plants became more pronounced at higher densities, leading to self-thinning effects, reduced individual plant vigor, and regulation of population size. Despite this, overall weed pressure remained high, contributing to significant suppression of wheat growth and yield under untreated conditions. Lower nitrogen levels reduced weed vigor but also negatively affected wheat competitiveness, highlighting the complex interaction between crop nutrition and weed dynamics. The study demonstrated that nitrogen availability plays a crucial role in shaping weed population structure and competitive interactions in wheat agroecosystems. The findings emphasize the importance of integrated nutrient and weed management strategies, including optimized nitrogen application and timely weed control, to minimize P. minor impact and improve wheat productivity.