K. Surekha

Grain Yield, Yield Components, Soil Fertility, and Biological Activity under Organic and Conventional Rice Production Systems

A field experiment was conducted for 2 years on a clayey Vertisol to compare the organic and conventional methods of rice farming. Two main plot treatments were with and without plant protection and four subplot treatments were (1) control (CON); (2) inorganic fertilizers (CF); (3) organics (OF), and (4) inorganics + organics (integrated nutrient management, INM). The organics were green manure, paddy straw, and poultry manure. After 2 years, the main plot effects were not significant in terms of crop productivity though there was a reduction in soil biological parameters. Increase in grain yield was larger with inorganics and INM as compared to the organics because of the higher panicle number. However, organics increased the microbial populations, biomass carbon, nitrogen, enzyme activities, and soil fertility as compared to inorganics. Thus, organics improved the nutrient availability by influencing the soil biological activity although it did not reflect in greater yields.

Productivity, Nutrient Balance, Soil Quality, and Sustainability of Rice (Oryza sativa L.) under Organic and Conventional Production Systems

A field experiment was conducted for 5 years (2004–2005 to 2009–2010) covering 10 crop seasons [five wet (WS; Kharif) and five dry (DS; Rabi)] at the Directorate of Rice Research farm, Hyderabad, India, to compare the influence of organic and conventional farming systems on productivity of fine grain rice varieties, cumulative partial nutrient balance, and soil health/quality in terms of nutrient availability, physical and biological properties, and sustainability index. Two main plot treatments were with and without plant protection measures, and four subplot treatments were (1) control (CON), (2) inorganic fertilizers (CF), (3) organics (OF), and (4) inorganics + organics (integrated nutrient management, INM). During wet season, grain yields with CF and INM were near stable (5.0 to 5.5 t ha−1) and superior to organics by 15–20% during the first 2 years, which improved with OF (4.8 to 5.4 t ha−1) in the later years to comparable levels with CF and INM. However, during DS, CF and INM were superior to OF for 4 consecutive years and OF recorded yields on par with CF and INM in the fifth year. The partial nutrient balance over 10 crop seasons for N and P was positive and greater with OF and INM over CF and for K it was positive with OF alone and negative with CF and INM. There were increases in SOC and available N, P, and K by 50–58%, 3–10%, 10–30%, and 8–25% respectively, with OF, over CF at the end of 5 years. The sustainability index (SI) of the soil system was maximum with organics (1.63) and CF recorded 1.33, which was just above the minimum sustainability index of 1.30 after 5 years. Thus, organic farming needs more than 2 years to stabilize rice productivity and bring about perceptible improvement in soil quality and sustainability in irrigated rice.

SRI-A Method for Sustainable Intensification of Rice Production with Enhanced Water Productivity

Climate change induced higher temperatures will increase crops’ water requirements. Every 10°C increase in mean temperature, results in 7% decline in the yield of rice crop. Hence, there is a need to develop water saving technologies in rice which consumes more than 50% of the total irrigation water in agriculture. System of Rice Intensification (SRI) is one such water saving rice production technology. Experiments were conducted at different locations in India including research farm of Directorate of Rice Research (DRR), Hyderabad, during 2005-10 to assess the potential of SRI in comparison to normal transplanting/Standard Planting (NTP/SP) under flooded condition. SRI recorded higher grain yield (6 to 65% over NTP) at majority of locations. Long term studies clearly indicated that grain yield was significantly higher (12-23% and 4-35% over NTP in Kharif and Rabi seasons, respectively) in SRI (with organic+ inorganic fertilizers) while the SRI (with100% organic manures), recorded higher yield (4-34%) over NTP only in the Rabi seasons. Even though, SRI resulted in higher productivity, the available nutrient status in soil was marginally higher (10, 42 and 13% over NTP for N, P and K, respectively) at the end of four seasons. There was a reduction in the incidence of pests in SRI and the relative abundance of plant parasitic nematodes was low in SRI as compared to the NTP. About 31% and 37% saving in irrigation water was observed during Kharif and Rabi seasons, respectively in both methods of SRI cultivation over NTP. SRI performed well and consistently reduced requirement of inputs such as seed and water in different soil conditions. SRI method, using less water for rice production can help in overcoming water shortage

Mechanized weed management to enhance productivity in System of Rice Intensification (SRI)

Rice ecosystems including irrigated rice in India is infested with complex weed flora including semiaquatic and aquatic weeds which cause yield losses from 15 to 76% in rice crop. ICAR-Indian Institute of Rice Research (IIRR) under All India Co-ordinated Rice Improvement Programme (AICRIP) has conducted experiments across India (11 locations) to evaluate System of Rice Intensification (SRI) method, assessing their potential and the effects of individual SRI practices for enhancing productivity under different agro-ecological conditions compared to standard normal transplanting (NTP) method. SRI method recorded significantly higher grain yield (6.22 t/ha) followed by integrated crop management (ICM) (6.07 t/ha), standard practice of transplanting (5.60 t/ha) and direct seeding with drum seeder (5.13 t/ha). The effect of cono-weedings on grain yield indicated the superiority of 4 times cono weeding (10, 20, 30 and 40 DAT) which recorded better yields over two times cono weeding and the reduction in yield to the tune of 5.7–11.8% by 2 times cono weeding i.e. 10 and 20 DAT (5.7% less) and herbicide application (11.8% less), respectively. Based on multi-location testing, results indicated that SRI has the potential to enhance the productivity of the rice with reduced inputs in different agro-ecological situation and soil types across the country and weeding by cono weeder with reduction in drudgery of weeding in rice.