Wheat (Triticum aestivum L.) being grown with association of boundary plantations of poplar (Populus deltoides M.) has to face competition for water and nutrients uptake. Field experiment was carried to study the dry matter accumulation pattern and nutrients uptake by wheat grown in association with boundary plantations of three- and four-year-old poplar plants under irrigated condition. Dry matter accumulation of wheat declined considerably due to presence of poplar tree line during all the growth stages as compared to pure crop. Maximum reduction in dry matter accumulation in wheat was observed near the tree line (0–3？m) under both three- as well as four-year-old plantation (21.1 and 17.8 per cent under three- and four-year-old trees, resp.) which tapered off beyond that, but synergetic effect caused by existence of trees increased dry matter significantly between 3–6？m distance and 6–9？m distance under both three- as well as four-year-old plantation. Similarly, minimum concentration of nutrients (nitrogen, phosphorus, and potassium) as well as their uptake in wheat plants was observed near the tree line (0–3？m) and increased subsequently with increase in distance from tree line. 1. Introduction Plantation of poplar (Populus deltoides M.) tree on the boundary of the agricultural fields is becoming popular among the farmers in Northern India. Wheat (Triticum aestivum L.) is one of the most important winter crops being grown in association with the plantation and one of the important agroforestry systems of the area [1, 2]. Since, agroforestry system involves mixture of species, they should share for resource utilization. Uptake of nutrients depends on the number, surface area, distribution, and effectiveness of the root system of individual species in the mixture. Being a perennial, tree root systems have the chance to explore larger area, both laterally and vertically and exploit zones of rich localized supply of nutrient with a result that the growth of the smaller understory species may be inhibited by competition for nutrients. It has been indicated that roots of fast-growing trees may extend laterally by at least 2？m each year [3]. Poplar is a fast-growing tree and has ability to provide substantial production [4, 5]. Toky and Bisht [6] noted that 60–80 per cent of the roots of 6-year-old poplar were present in the upper soil layer (0–45？cm). However, maximum fine roots were concentrated in 15–30？cm soil depth. Thus, the bulk of roots were quite close to surface, and therefore, root competition with agricultural crops is likely. Fast-growing and
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