The São Paulo State Legislation established a gradual increase in the use of mechanical sugar cane harvest, which leaves a thick layer of straw, possibly affecting the development of purple nutsedge. Purple nutsedge (Cyperus rotundus L.) is one of the most crop-damaging weeds, infesting wide areas mainly in tropical and sub-tropical regions, causing substantial yield losses. It is considered one of most important weeds in sugar cane crop, by interfering directly on plant development, competing for essential growth factors (such as water, light, and nutrients) and by releasing allelopathic substances. There are few works about the effect of tuber size of weed species on the germination and development of plants. This experiment aimed to verify if the addition of sugar cane straw could affect the development of the aboveground part of purple nutsedge derived from tubers of small (0,2 to 0,3 g) and large (1,0 to 1,1 g) sizes, planted at three different times of the year. The experiment was set up in a greenhouse in Campinas, State of São Paulo, arranged in a randomized block design with four replicates. Dormant purple nutsedge tubers of small and large sizes were planted in May, July and September, and RB 855156 sugar cane straw was added in quantities corresponding to 0,0, 5,0, 10,0 and 15,0 ton/ha. Every 28 days until 84 days after each planting, the number of emerged sprouts, average plant height, foliar area and fresh and dry leaf and total aboveground part (leaves + inflorescences) weights were evaluated. The tubers planted in May emerged sooner and more uniformly than those planted in July and September. The number of emerged sprouts was not affected by tuber size. On the other hand, plant height, leaf area, and fresh and dry leaf and aboveground part weights were larger when originated from large-sized tubers. The addition of sugar cane straw to the soil affected more the plants derived from small than from large tubers. It was verified that, with the exception of average height, the September planting originated plants with larger number of sprouts, leaf area, fresh and dry leaf and total aboveground part weights. Larger average plant height values were observed in the May planting. For all analyzed variables, the July planting presented always the smallest values. The application of increasing quantities of sugar cane straw caused a decrease in the number of sprouts, foliar area, and fresh and dry leaf and total aerial aboveground weights. The number, leaf area, and average plant height of the sprouts, and the fresh and dry leaf and total aboveground part weights increased linearly as function of time.
Sugar cane harvest straw; Cyperaceae; bud sproutings
