Soil management: The key factors for higher productivity in the fields utilizing the system of rice intensification (SRI) in the central highland of Madagascar

Towards an understanding of the high productivity of rice with System of Rice Intensification (SRI) management from the perspectives of soil and plant physiological processes

“…Few reports were available about the effect of N application rate on the growth and yield of rice under SRI (Lin et al 2009;Zhao et al 2009), because N fertilizer was not widely referred to SRI practices (Thakur et al 2010b) and more organic matter was commonly applied to SRI fields than to conventional practice fields (e.g., Tsujimoto et al 2009). The application of N at the rate of greater than 180 kg ha À1 (which included compost as an N source) recorded a maximum yield of 9.5 t ha À1 for hybrid rice grown under SRI, while the yield of hybrid rice grown conventionally with the same N dose by chemical N fertilizer, was 7.7 t ha À1 and yield increased with more N (Lin et al 2009).…”

“…The management practices of system of rice intensification (SRI) include the following points: (1) the age of seedlings at transplantation is less than 15 days (two-tothree-leaf stage); (2) seedlings are transplanted with wide spacing, and one seedling per hill; (3) water management is undertaken to maintain paddy soils in mostly aerobic condition, e.g., by small daily applications of water with no flooding, AWD, shallow water management from PI to harvest, and also active soil aeration through mechanical weeding, and application of organic matter for improving soil structure and function as well as nutrient availability (Dobermann 2004;Tsujimoto et al 2009;Thakur 2010;Thakur et al 2010b). Although these practices might affect the synergistic effects on the growth and yield of the rice plant, each factor should be verified by scientific methods.…”

“…The average amount of mineralizable N was 116.8 mg kg À1 at the SRI field, while it was 65.6 mg kg À1 at the conventional field. They concluded that soil fertility, represented by the soil available N, was the main factor for the higher yield (Tsujimoto et al 2009). …”

“…(Zhao et al 2009). The SRI fields in Madagascar have been continuously plowed to a depth of 25 to 30 cm by double-digging since the adoption of organic matter application in the early 1990s, while conventional fields were plowed 10 to 20 cm (Tsujimoto et al 2009). The depth of the plowed layer was not reported in other references, but the management practices of SRI often include application of compost or other organic amendments (Thakur et al 2010b).…”

“…Although the reports did not describe experimental details, they suggested that drier upland Rayalseema districts gave the best response to SRI methods rather than the low-lying coastal districts where soils are more saturated. Tsujimoto et al (2009) investigated the factors for high yield (7.0-9.9 t ha À1 ) of an SRI farmer's plot by comparing it with the conventional farmers' plot (2.6-5.0 t ha À1 ). Average plowing depth of SRI and conventional management fields was 28.8 cm and 12.5 cm, respectively.…”