Amend the soil with crops grown as green manures
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
Green manures are growing crops that are ploughed under to enrich the soil.
Supporting evidence from individual studies
A controlled, randomized, replicated experiment in 2000-2002 on clay loam in India (Ramesh & Chandrasekaran 2004) found 10.6% higher soil organic carbon when sesbania Sesbania rostrata was included in cropping, compared to continuous rice Oryza sativa. There were five combinations of rice and sesbania consisting of: fallow-rice-rice, sesbania-rice-rice, sesbania-rice-sesbania-rice, sesbania-rice-rice-sesbania, and sesbania-rice-sesbania-rice-sesbania. Each combination was divided into four manure treatments: control (none applied), farm yard manure (12.5 t/ha), poultry manure (5 t/ha), and dual cropping with fern Azolla hybrid. There were three replication of each crop combination. Plot size was not specified. Soils were sampled after each rice harvest (depth not specified).Study and other actions tested
A controlled, randomized, replicated experiment in 2007-2008 on clay loam in Pakistan (Ali et al. 2012) found the highest rice yield after a sesbania Sesbania rostrata green manure (3.73 t/ha), then mungbean Vigna radiata (3.57 t/ha) and berseem Trifolium alexandrinum (3.53 t/ha) green manures, compared to the rice Oryza sativa-wheat Triticum aestivum only rotation (2.59 t/ha). Wheat yield was also higher under sesbania (2.81 t/ha), mungbean (2.69 t/ha) and cowpeas Vigna unguiulata (2.63 t/ha) compared to rice-wheat only (2.59 t/ha). Soil organic carbon increased from 0.67% to 0.72% (of total soil collected) during the experiment. Four green manures were grown and harvested prior to the planting of a rice-wheat rotation, which included: mungbean, cowpeas, sunflower Helianthus annuus, sesbania. Three more green manures were sown after harvesting the rice crop including: berseem, lentil Lens culinaris, canola Brassica napus. These were compared to a rice-wheat crop only rotation. All green manures were incorporated into the soil before rice or wheat was transplanted or sown. Plots were 10 x 14 m. There were three replicates. Soils were sampled before sowing and after harvest of the rice-wheat crops to 20 cm depth.Study and other actions tested