Amod K. Thakur

AN ASSESSMENT OF PHYSIOLOGICAL EFFECTS OF SYSTEM OF RICE INTENSIFICATION (SRI) PRACTICES COMPARED WITH RECOMMENDED RICE CULTIVATION PRACTICES IN INDIA

An evaluation was conducted in eastern India over three years, 2005–2007, to compare the performance of certain System of Rice Intensification (SRI) practices: transplanting single, young (10-day-old) seedlings in a square pattern; no continuous flooding; and use of a mechanical weeder – with those currently endorsed by the Central Rice Research Institute of India, referred to here as recommended management practices (RMP). All plots received the same fertilization, a combination of organic and inorganic nutrients, and the SRI spacing used was 20% less than usually recommended. Accordingly, the results reported here are designated as a modification of SRI recommendations (SRI m ). The objective of this research was to understand the benefits in terms of yield and other physiological parameters, if any, from using most if not all recommended SRI practices compared to RMP. These selected SRI practices out-yielded RMP by 42%, with the higher yield associated with various phenotypical alterations, which are reported here. Significant measurable changes were observed in physiological processes and plant characteristics, such as longer panicles, more grains panicle −1 and higher % of grain-filling. The decreased plant density with SRI m management was compensated for by increased per-plant productivity. SRI m hills with single plants were found to have deeper and better-distributed root systems, higher xylem exudation rates, more open plant architecture with more erect and larger leaves, and more tillers than did RMP hills having multiple plants. Due to the reduction in number of hills m −2 in SRI m plots compared to RMP, no significant difference was found in root dry weight or leaf number, tillers or panicle number on an area basis. Nevertheless, in spite of SRI m having fewer hills and fewer tillers per unit area, the leaf area index (LAI) with SRI m practice was greater due to larger leaves. These together with altered plant architecture, contributed to more light interception by SRI m plants. The higher leaf chlorophyll content at ripening stage reflected delayed senescence and the greater fluorescence efficiency (Fv/Fm and ФPS II) associated with SRI m practices contributed to more efficient utilization of light and a higher rate of photosynthesis, which was probably responsible for the observed increase in grain filling and heavier grains compared to RMP plants. The higher photosynthesis rate coupled with lower transpiration in SRI m plants indicated that they were using water more efficiently than did RMP plants. The latter produced 1.6 μ mol CO 2 fixed per m mol water transpired, compared to 3.6 μ mol CO 2 in SRI m plants.

Performance evaluation of rice varieties under the System of Rice Intensification compared with the conventional transplanting system

A field experiment was conducted at Deras Research Farm, Khurda district, Bhubaneswar, Orissa, India, to evaluate the performance of different rice varieties managed under System of Rice Intensification (SRI) compared with the current transplanting system (CTS). Five rice varieties were used for the study: (i) Khandagiri (early-duration, 90 days); (ii) Lalat (early-medium duration, 110 days); (iii) Surendra (late-medium duration, 130 days); (iv) Hybrid CRHR-7 (late-medium duration, 135 days); and (v) Savitri (long-duration, 145 days). It was seen that SRI practices significantly (p < 0.05) improved the harvest index, percentage of effective tillers, panicle length, and various yield components in all the varieties. SRI hills having an open-canopy structure with higher leaf area index (LAI) resulted in greater light interception than the conventional transplanting methods. At the ripening stage, SRI plants had better root growth and a higher xylem exudation rate than CTS plants. This was associated with higher levels of chlorophyll in the lower leaves and a higher photosynthesis rate. Delayed senescence with enhanced photosynthesis in the lower leaves was also responsible for supplying more assimilates toward the roots for maintaining their higher activity. These features might also contribute to the improvement of grain filling and grain weight in SRI-grown plants as all the varieties performed better in terms of grain yield (12–42% higher) with this alternative management.

System of crop intensification for more productive, resource-conserving, climate-resilient, and sustainable agriculture: experience with diverse crops in varying agroecologies

ABSTRACT With continually increasing demand for food accompanied by the constraints of climate change and the availability and quality of soil and water, the world’s farmers are challenged to produce more food per hectare with less water, and with fewer agrochemical inputs if possible. The ideas and methods of the system of rice intensification which is improving irrigated rice production are now being extended/adapted to many other crops: wheat, maize, finger millet, sugarcane, tef, mustard, legumes, vegetables, and even spices. Promoting better root growth and enhancing the soil’s fertility with organic materials are being found effective means for raising the yields of many crop plants with less water, less fertilizer, reduced seeds, fewer agrochemicals, and greater climate resilience. In this article, we review what is becoming known about various farmer-centred innovations for agroecological crop management that can contribute to agricultural sustainability. These changes represent the emerging system of crop intensification, which is being increasingly applied in Asian, African, and Latin American countries. More research will be needed to verify the efficacy and impact of these innovations and to clarify their conditions and limits. But as no negative effects for human or environmental health have been identified, making these agronomic options more widely known should prompt more investigation and, to the extent justified by results, utilization of these methodologies.