Cotton Seedling Root Growth Responses to Light Reflected to the Shoots from Straw‐Covered versus Bare Soil

Abstract

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 determinw whether the light spectrum reflected from wheat straw to the cotton seedlings could be a contributing factor. Cotton was planted in 3 L pots of loamy sand which was screened to remove old plant 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 centered over each pot. Panels were covered with fresh wheat straw, weathered straw, or bare soil so that different far‐red to red( FR/R) light ratios were reflected. Insulation maintained the same soil temperature (±0.5) in all pots regardless of surface cover. Each pot was thinned to a single seedling that emerged on the same day. Leaf area and stem length were measured on seedlings cut at the soil surface 1 wk after emergenc. Roots were washed free of soil, spread on paper, covered with transparent plastic, and photocopied. Root lengths were measured on the photocopies. Stems, leaves, and roots from each plant were dried and weighed. The fresh wheat straw reflected the highest FR/R ratio and resulted in seedlings with the least root length, lowest root weight, longest stems, and lowest root/ shoot weight ratio. This 2‐yr glasshouse study show that the spectral environmen over fresh straw can contribute to modified seedling morphology and suggests that it should be considered when developing management practices for no‐till double‐crop cotton.