Water retention properties of maize stem residue as affected by particle size and decomposition in soil

The aim of this study was to investigate the effects of crop residue particle size and decomposition on water retention properties. Two pieces of 0.5 and 5 cm length of intact maize stem were chosen as experimental model. Maize particles were incubated in soil during 49 days at 24°C to alter the characteristics of stem particles by decomposition. Maximum water retention and residual humidity of particles were established by immersing the particles at three decomposition stages (undecomposed, decomposed after 14 days and after 49 days) for different duration of time until stable weight. We observed that 0.5 cm particles absorbed the same amount of water per g of residue as 5 cm particles. Decomposed particles absorbed more water than undecomposed ones for both particle sizes. Similar trends were obtained for residual water. We hypothesized that higher maximum water absorption and lower residual water retention in decomposed particles were due to an increase in residue porosity during decomposition. Particle size affected C mineralization with significant higher mineralization for 0.5 cm particles (29% of added C) than for 5 cm particles (21% of added C). The consequences of water retention properties on residue mulches are discussed in the context of conservation agriculture.