Biochemical Properties of Decomposing Cotton and Corn Stem and Root Residues

Abstract

Maintaining soil C is especially difficult in hot climates. Information is needed regarding the influence of residue biochemical properties on decomposition in hot, semiarid climates so that management practices can be developed that improve organic matter retention. Litterbags containing stalk or root tissues of senescent cotton (Gossypium hirsutum L.) or corn (Zea mays L.) were placed on the surface or 10 cm below the surface of a fallow Hidalgo sandy clay loam (fine‐loamy, mixed, hyperthermic Typic Calciustoll) near Weslaco, TX, USA (26°9′ N lat., 97°57′ W long.), and were monitored quarterly for 1 yr for changes in mass, water‐extractable C (WEC), water‐ and alcohol‐extractable polyphenolics (WEP and AEP, respectively). Surface‐placed cotton residues retained more mass than when buried, from approximately 80% (surface) to <50% (buried). For corn, retention ranged from approximately 60 to approximately 70% for surface residues to approximately 40% for buried residues. Most mass loss occurred within the first three months. The greatest increases in WEC (approximately 1500 μg C g−1 for corn; approximately 500 μg C g−1 for cotton) and WEP (approximately 175–325 μg g−1) for corn also occurred within the first 3 months. Water‐extractable polyphenolics peaked (about 100 μg g−1) in cotton residues at 6 mo, while corn residues reached a maximum (approximately 300 μg g−1) at 3 months. Over a year, AEP decreased in cotton stem residues, from approximately 5 to 8 to approximately 2 μg g−1 Surface cotton roots maintained approximately 6 μg g−1 after three months. Results illustrated the importance of residue moisture content during decomposition, and indicate that different residues may have different capacities to hold moisture, which may affect the biochemical characteristics and kinetics of decomposition.