Effect of environmental conditions on emergence and growth of warm season grass

The effects of environmental conditions on the emergence and growth of warm season grass, the regrowth vigour after cutting and others were studied as compared with weeds. The results were as follows: 1. It was estimated that the competitive weeds of warm season grass were common lamb's-quarters (Chenopodium album L.), Polygonum lapathifolium L. subsp. nodosum Kitam., and livid amaranth (Amaranthus lividus L.) in case of seeding from April to the first ten days of May (the average daily air temperature 10-15°C), and large crabgrass (Digitaria adscendens Henr.), common purslane (Portulaca oleracea L.) and Chufa (Cyperus microiria Steud.) in case of seeding on the last ten days of May or later (over 20°C) in the Kanto plain. 2. African millet (Eleucine coracana (L.) Gaerth.) surpassed other species in low temperature germeability and grew rapidly after emergence. Low temperature germeability of Rhodes grass (Chloris gayana Kunth) was inferior to African millet or P. lapathifolium L., but was superior to large crabrass. The early growth of Rhodes grass was about the same as large crabgrass at the conditions of the average daily air temperature 15-25°C. 3. Soil moisture content affected greatly the emergence and growth of Rhodes grass. Namely, both emergence and growth in 6mm watering per day were better than 4 or 2mm watering, and 2mm watering was extremely inferior to others. 4. The ability of regrowth by cutting after shading treatment of Rhodes grass was stronger than African millet. The growth of African millet was supressed in shading condition. 5. Large crabgrass, livid amaranth and common purslane had the ability of strong regrowth after cutting, and Chufa was medium. P. lapathifolium L. and common lamb's-quarters were weak.