Rice (Oryza sativa L.) is one of the most important staple food crops in the world. In Asia, more than two billion people are getting 60-70 percent of their energy requirement from rice and its derived products. In India, rice occupies an area of 44 million hectares with an average production of 90 million tonnes at productivity of 2.0 tonnes per hectare.
It is estimated that 140 million tones of rice would require by 2025 in India. Therefore to sustain present food self-sufficiency and to meet future food requirement, India has to increase its rice productivity by 3 per cent per annum.
The present production trend showed decline in productivity, mostly because of imbalanced use of fertilizers and pesticides, over-exploitation of the natural resources, particularly water, deterioration in physical conditions of the soil and emergence of new bio-types of pests and diseases. These led to yield stagnation, causing concern about the future potential for productivity growth and long-term sustainability.
Thus the major challenge before the researcher is to innovate appropriate technologies to produce more food from diminished land resources for the burgeoning population pressure and to improve as well as conserve the natural resources of small and marginal farmers who contribute the greatest in this important production system.
Possible options for further increase in rice production is through the application of new technologies such as system of rice intensification (SRI), laser land levelling of field, crop diversification and site-specific nutrient management and along with application of resource conserving techniques refer to those practices that conserve resources and ensure their optimal utilization and input use-efficiency. Suitable technologies need to be practice to address the specific concern which is prevailing in specific areas.
Concern issues in rice production :
Soil degradation: Rice is grown predominantly under anaerobic soil condition. Puddling reduces infiltration of water at the risk of destruction of structure However, destruction of soil aggregates due to puddling in rice results in poor tilth and increases soil strength in the surface and subsurface layers, decreases hydraulic conductivity and infiltration, and inadequate charging of the soil profile for the rice crop.
Decline water table: Rice is a water-guzzling crop. To fulfill its requirement water excessive pumping of underground water leads to decline in water table. The farmers are shifting from centrifugal pumps to submersible pumps extract water from the lower strata.
Inadequate plant population: To harvest optimum yield of rice, 33 hills /m2 are required but usually in farmers’ fields it varies from 18 to 22 hills/ m2.
Drop in soil organic matter: Long-term experiments conducted in Indo-gangetic plain revealed that the yields of rice was constantly greater in all the years when complete doses of NPK were applied through fertilizers or 50% doses of NPK were applied through fertilizers along with organic materials compared with that of unfertilized control.
Nitrate pollution in ground water: Pollution of ground water owing to leaching of nitrates appears to be a serious concern in rice crop. Which requires more than 300 kg N/ha. The situation is worse in coarse-textured soils where use of N fertilizer is still higher with excessive irrigations.
Emergence of multiple nutrient deficiencies: In recent years, deficiencies of Mn in salt-affected soils of Punjab and B in calcareous soils of Bihar have become evident. In the highly permeable soils of Punjab, wheat grown after rice suffered from Mn deficiency.
Appearance of new weed biotypes and resistance to applied herbicides: Many new weed species have emerged in rice crop such as ghrilla ghas, wrinkle grass and broad-leaved weeds, which is not controlled by the commonly recommended herbicides. Wrinkle grass is not controlled by butachlor application.
Inadequate and imbalanced use of fertilizer: The farmers in general are applying N and P but not K. The appropriate N: P: K ratio of 4: 2: 1 is not being followed. The excessive use of N leads to lodging and greater incidence of pests and diseases and which leads toward lower and uneconomical yield.
Weather aberration: The erratic distribution of rainfall in time and space also affects the crop yield at great extent.
Resource Conserving Technologies for sustaining production of Rice
Resource conserving techniques (RCTs) refer to those practices that conserve resources and ensure their optimal utilization and enhance or input use-efficiency.
These techniques include zero or minimum tillage (save fuel), permanent or semi permanent residue cover, new varieties that use nitrogen more efficiently, laser land levelling that save irrigation water system of rice intensification (SRI), direct seeded rice (DSR), use of leaf colour chart (LCC) for precision application of nitrogen. Some important RCTs have been discussed here.
Zero tillage is an extreme form of conservation tillage (CT) in which mechanical soil manipulation is reduced to traffic . It helps in paradigm shift in crop production. The current and potential area is 2.0 m ha and 10 m ha under zero tillage in India, respectively.
It is very helpful in the area of intensive cultivation where a turnaround period between two crops is very less and thus it can facilitate timely sowing. Some advantages of the zero tillage are as follows:
- Saving of fuel and labour cost.
- Reduced cost of cultivation.
- Saving approximately Rs. 3000/ ha towards field preparation.
- Timely planting gave yield advantage approximately 2 q/ha.
- Reduces soil erosion and improves soil health.
Direct seeded rice:
Rice can be directly seeded either through dry or wet or germinated seeds. Dry seeding of rice can be done by drilling the seed into a fine seedbed at a depth of 2–3 centimeters. Wet seeding requires levelled fields to be harrowed and then flooded.
The field is left for 12–24 hours after puddling, then germinated seeds (48–72 hours) are sown using a drum seeder. Indeed, weed management is a critical factor in direct seeded rice.
Timely application of herbicides (eg pretilachlor or butachlor at 2-3 DAT) and one or two hand weeding provide effective control
Crop residue management:
Crop residues are the parts of plants left in the field after the crops have been harvested and thrashed. Crop residues are good sources of plant nutrients, are the primary source of organic material added to the soil, and are important components for the stability of agricultural ecosystems
Crop residue is not a waste but rather a tremendous natural resource.
Laser land leveling:
It is a precursor of resource conserving technique and a process of levelling the land surface (± 2 cm) from its average elevation using laser equipped dragged buckets. It levelled the surface having 0 to 0.2 % slope so that there is uniform distribution of water may takes place and thus enhance water use efficiency.
Advantages of laser land leveling are as follows:
- About 4% rise in area under cultivation due to removal of bunds and channels.
- Saves 10-15% water due to uniform distribution.
- Increases resource (N and water) use efficiency.
- Reduces cost of production and Enhances productivity.
Brown Manuring :
Sesbania sown along with rice crop and after 30-35 days sesbania crop sprayed by 2,4-D which turned sesbania crop in brown colour and leaves starting falling while rice crop is resistance to 2,4-D. brown manurig adding some benefits such as
- No need additional irrigation water for raising a sesbania crop in summer before rice when evaporate demand are close to 10-13 mm/days.
- Brown manuring keep the moist soil for long time.
- Improving soil fertility.
- Help in weed control .
Leaf colour chart:
Leaf colour chart popularly known as LCC now used in determination of leaf nitrogen content based on chlorophyll content in the leaves at different growth stages. A LCC value of 4 indicates that there is 1.4 to 1.5 mg N / g leaf weight.
The critical LCC value for rice hybrids and HYVs is 4 and for and basmati rice is 3. These values have to taken from 7-10 DAS or 20-25 DAT to heading.
- Resource Conserving Techniques are more effective in combinations rather than their individual application.
- SRI method of rice cultivation is an efficient in natural resources utilization and it is a solution for enhancing the production and productivity.
- Among different water-wise rice establishment techniques DSR is cost-effective and gives a higher net return.
- Sesbania brown manuring is helpful in suppressing weeds and increases the yield.
- LCC save nitrogen approximately 25%.
- Diversification of rice based cropping sequence is a need of the hour for sustainable production.
- Site specific nutrient management in rice (SSNM) is helpful to achieve higher yield.
- Laser land leveling enhances the yield and water productivity.
Anita Meena, Rajpal Meena, Sonia Sheoran, Rekha Malik, Ajay Verma and R.K. Sharma
Indian Institute of Wheat and Barley Research (IIWBR), Karnal