Rice is the most common staple food in Asia, where about 90% of the world’s rice is produced and consumed. India produced nearly 43 million ha. In the warm season, rice is usually planted as an annual plant. It can be grown in a wet (paddy) or dry (filed) environment. About 75% of the global rice production comes from irrigated rice systems because most rice varieties express their full yield potential when water supply is adequate. The total plant nutrients removed from the field by grain rice is different from the amount plant uptake during the growth period of straw and grain together.
Nitrogen improves plant height, panicle number, leaf size, spikelet number, and full spikelet number, all of which influence a rice plant's yield potential. The number of tillers that emerge during the vegetative stage has a big impact on panicle number. The reproductive stage determines the quantity of spikelet’s and the number of filled spikelets. Urea is the most common nitrogen fertilizer used in rice fields. Nitrogen fertilizer applied to the rice crop is partially lost through different mechanisms including ammonia volatilization, denitrification, leaching and runoff losses.
Losses of fertilizer in field
Fertilizer nitrogen may be lost from the soil in several different ways, including; ammonia volatilization, nitrate leaching and nitrate denitrification and runoff losses. Factors affecting these losses include fertilizer compound, fertilizer form, type of application, timing of application, soil properties, rainfall amount and intensity, and temperature and wind after application.
Ammonia volatilization -Ammonia volatilization is a chemical process in which ammonium from urea or ammonium-containing fertilizers (e.g. urea) are transformed to ammonia gas at high pH at the soil surface. When fertilizer is integrated, losses are minimal, but when fertilizer is placed on the surface, losses might be significant.
Nitrate denitrification- Nitrate denitrification is a biological process that happens in the soil profile when there are enough accessible nitrates, a labile carbon substrate, and low oxygen levels, as in slow-draining soils. In most dryland agricultural soils, losses are minimal, but in waterlogged circumstances, losses can be significant.
Nitrate leaching- Nitrate leaching a physical process that occurs with the drainage of water through the profile. While nitrate movement within the profile is common in cracking clay soils, large-scale loss of nitrate below the root zone is minimal in most conditions.
Runoff losses- Nitrate can get into water directly as the result of runoff of fertilizers containing nitrate which increase load of nitrogen into rivers and streams.
These losses may cause environmental problems such as polluting the atmosphere, aquatic system and ground water. The recovery of fertilizer N applied to rice seldom exceeds 30-40%.Fertilizer N use efficiency in lowland rice may be maximized through a better timing of application to coincide with the stages of peak requirement of the crop, and placement of N fertilizer in the soil with control release.
However, nitrogen losses can be reduced a considerable extent by various methods, mud ball urea application one of among them.
Mud ball technique
The International Rice Research Institute in the Philippines proposed the mud ball application technique. It involves the use of a small amount of fertilizer, especially urea placed in the center of the mud ball which is dried and placed in the rice field at the appropriate time.
Mud ball urea is act as a slow-release fertilizer so it makes long time availability of nitrogen to crop. Also, The International Rice Research Institute show that mud ball technique is superior to other methods of fertilizer application like broadcasting, top dressing and foliar spray.
Pre-requisite conditions required
The application of mud ball urea necessitates the fulfillment of certain parameters such as it is laborious work, so it will be more profitable for the farmers having 5-6 family labor. It is also useful for the small famers (less than 1 acre) and more suitable for low land conditions. This technique may be used in both irrigated and non-irrigated farms. However, better results may be obtained in irrigated farms.
Method of preparation for urea balls formation
A hectare of field necessitates around 62,500 mud balls. Each mud ball should have a diameter of 3cm. To begin, construct a mud ball and use your thumb to make an opening in the center, then place the fertilizer in the space and enclose the mud ball. Immediately after transplanting or during transplanting insert the mud balls 10-12 cm beneath the soil surface in the center of every four rice hills. During this period, the paddy should contain the water level to be 1-3cm.
Surajit K. De Datta, the head of the IRRI's agronomy department, which is conducting the research. "Applying fertilizer using the mud ball technique results in significantly higher yield at lower fertilizer rates". If you use the broadcast approach during the dry season, you'll need 100 kilograms of fertilizer per hectare; if you utilize the mud ball method, you'll only need 60 kilograms -saving 40% of fertilizer with no reduction in grain yield. You also save more fertilizer during the rainy season, when you only need 30 kilos of nitrogen per hectare rather than the 60 kilograms of nitrogen needed when other methods are used. In addition, you fertilize only once if you use the mud ball method, whereas you fertilize two or three times if you use the broadcast method”.
Mud ball technique benefits
As in the low land paddy condition the nitrogen use efficiency was low i.e. 28-34% so by the use of mud ball urea the nitrogen use efficiency increases and also it has less detrimental effect to the environment and the formation of mud ball urea is simple. However, when applying the urea, we have followed some precautions, such as not use sandy soil for the production of mud balls.
Limitations
Fertilizer mud balls have been tested in farmer's fields in the Philippines, Thailand, and India, and the results have been encouraging. However, no one is utilizing this technique on a wide scale, mainly due to the fact that it is very time consuming .“I don’t think many farmers will be willing to work so hard preparing thousands of mud balls just to save on fertilizer,” De Datta adds. “As a result, we don't recommend the practice to every Asian farmer." De Datta, on the other hand, argues that small farmers should employ the mud ball technique "as long as they are willing to work hard and use family labor." If you hire labor, the fertilizer savings will almost certainly surpass the labor cost.”
Future perspective
According to De Datta, IRRI experts are exploring for a faster, less time-consuming way to implement the mud ball concept. "Our technical department has created a machine that can directly place fertilizer 10 to 12 centimeters into the soil."
He further said that if urea briquets, which are currently being tested by the Tennessee Valley Authority in the United States, become commercially available, mud balls won’t be necessary, and labor expenses will be significantly reduced. Urea briquets, which are solid six-gram pellets, can be buried in the soil without being encased in mud balls. The briquets have been examined, according to De Datta, “and these give similar satisfactory results.”
Authors
Rajni Yadav1, Anil Kumar2, Sandip Kumar Gautam1, Manu Rani1
1Department of Soil Science, Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana; 2Janta Degree College, Auraiya, Uttar Pradesh
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