Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 1997
Publication Date: N/A
Interpretive Summary: Poor seedling establishment may occur if straw remains on the soil surface when double-cropping cotton after wheat harvest. Seed germination and early growth might be affected by (a) poor seed to soil contact, (b) cool soil temperature, or (c) the spectrum of light reflected from the straw to the new seedlings. Our objective was to test the effect of reflected light while minimizing effects of soil to seed contact and low soil temperature. Cotton seeds were planted in pots of loamy sand that were covered with styrofoam insulation panels. The insulation panels were covered with fresh wheat straw, weathered straw or soil. The straw or soil above the panels affected the ratio of far-red to red light (FR/R) reflected to the seedling shoots. However, soil temperatures below the insulation panels were very similar. The fresh straw reflected the highest FR/R ratio and seedlings grown over fresh straw had the longest stems, heaviest shoots, least root length, least root weight and a much lower root to shoot weight ratio than seedlings grown over bare soil. Affects of weathered straw were between those of fresh straw and bare soil. In addition to the well-known affects of fresh straw on seed to soil contact and soil temperature, spectra of light reflected from fresh straw can influence early root growth and spindliness of seedling stems.
Technical Abstract: Poor seedling establishment may occur if straw remains on the soil surface when double-cropping cotton (Gossipium hirsutum L.) after wheat (Triticum aestivum L.) harvest. Effects of straw-covered versus bare soil on spectrum of light reflected to cotton seedling shoots and on root/shoot growth relationships were studied. Seedlings were grown in pots of loamy sand. Pots were arranged in groups of five and each group was covered with a styrofoam insulation panel. Holes were cut in panels so that a hole was centered over each pot. The panels were covered with fresh wheat straw, weathered straw, or bare soil. Soil temperatures did not differ more than 0.5 degree C among the pots below the insulation panels. However, the different colored straw and soil reflected different far-red to red light (FR/R) ratios. Seedlings were cut at the soil surface seven days after emergence and evaluated for root and shoot development. The fresh wheat straw reflected the highest FR/R ratio and seedlings developed the least root length, lowest root weight, longest stems, heaviest shoots, and lowest root/shoot weight ratio. Root and shoot growth responses to light reflected from fresh straw should be considered in management of cotton seedling establishment in double-crop no-till systems.