Soil properties affected by combinations of soil solarization and organic amendment

A field experiment was conducted to investigate the effects on soil properties of solarization combined with rice bran additive. The treatments included control (bare soil), black polyethylene film mulch (BM), clear polyethylene film mulch (CM), rice bran mixture (RBMx), rice bran mulch (RBM), rice bran mixture and black polyethylene film mulch (RBMx + BM), rice bran and black polyethylene film mulch (RBM + BM), rice bran mixture and clear polyethylene film mulch (RBMx + CM), and rice bran and clear polyethylene film mulch (RBM + CM). Initially, 15 kg m⁻² of rice bran was applied to each treatment as the organic amendment. A cover of black or clear polyethylene film was then used to begin the soil solarization process. Approximately 49 days later, the polyethylene film was removed and five broccoli seedlings per replication were planted 6 weeks later. The combination of rice bran mixture with the clear/transparent polyethylene film mulch (RBMx + CM) raised both the mean and maximum soil temperatures over 0–30 cm of soil depth. Maximum soil temperature under the RBMx + CM treatment was the highest of all treatments (77°C) and were about 32°C greater than under the control, while it was only 52°C under RBM + BM treatment. Combining rice bran with clear/transparent polyethylene film mulch during the soil solarization process is recommended for raising soil temperatures. Further investigation over a longer period of soil solarization process with rice bran–organic amendment and polyethylene film mulch combinations is required to more accurately determine their effects on soil properties and crop production.