Cotton seedling root growth responses to light reflected to the shoots from straw-covered versus bare soil

Poor seedling establishment can severely impact cotton (Gossypium hirsutum L.) when grown in a double-crop sequence following wheat (Triticum aestivum L.). My objective was to determine whether the Light spectrum reflected fr om wheat straw to the cotton seedlings could be a contributing factor. Cott on was planted in 3 L pots of loamy sand which Has screened to remove old p lant residue. Pots were arranged in groups of five and covered with 122- by 122- by 2- cm polystyrene foam insulation panels which had 5-cm holes cent ered over each pot. Panels were covered with Fresh wheat straw, weathered s traw, or bare soil so that different far-red to red (FR/ R) light ratios we re reflected, Insulation maintained the same soil temperature (+/- 0.5) in all pots regardless of surface cover. Each pot was thinned to a single seed ling that emerged on the same day. Leaf area and stem length were measured on seedlings cut at the soil surface 1 wk after emergence. Roots were washe d free of soil, spread on paper, covered with transparent plastic and photo copied. Root lengths were measured on the photocopies. Stems, leaves, and r oots from each plant were dried and weighed. The fresh wheat straw reflecte d the highest FR/R ratio and resulted in seedlings with the least root leng th, lowest root weight, longest stems, and lowest root/ shout weight ratio. This 2-yr glasshouse study shows that the spectral environment over fresh straw can contribute to modified seedling morphology and suggests that it s hould be considered when developing management practices fur no-till double -crop cotton.