Nitrogen, amino and nucleic acid is an essential element for the formation of nucleotides and chlorophyll. It increases plant height and tillering and encourages rapid development. At the same time; It also increases leaf size, number of spikelets per cluster, number of full grains per cluster, and grain protein content. As a result, we can say that nitrogen affects all parameters that contribute to yield. There is a close relationship between the nitrogen content of the leaf and the production of photosynthesis and biological yield. When a sufficient amount of N is applied, the product's need for other elements such as P and K increases (Doberman and Fairhurst, 2001).
Nitrogen is needed during the entire development period of the plant. However, it is most needed between the early seedling stage and the middle of tillering and at the beginning of the cluster formation stage. During the grain filling period, it is important to provide enough nitrogen to delay leaf death and increase photosynthesis production.
Changes caused by nitrogen application in the development of rice plant (De Datta, 1981).
– It gives a dark green appearance to the stem and leaves of the plant,
– Accelerates development or increases plant height and tillering,
– Increases leaf and grain sizes,
– The number of spikelets and fertile grains increases in the cluster,
– Grain protein content increases.
Symptoms that may occur in nitrogen deficiency;
– Short plants with few siblings,
– The leaves are narrow, erect and yellowish green,
– Old leaves turn straw color and die.
Amount of Nitrogen to Use
Nitrogen requirement varies according to soil type, variety, planting time, use of weed pesticides and nutrient residues left by previous crops in the soil. Less nitrogen is used in cases where new paddy rice is planted, weak stem varieties are planted, legume plants are grown before and planting is delayed. Higher doses of nitrogen fertilizer are used for optimum plant growth and high yields in fields where rice is planted continuously and in fields where early sowing is made. Excessive use of fertilizers; It can cause a decrease in yield due to lying and the emergence of some fungal diseases.
Murayama (1979) stated that plants take 19-21 kg of nitrogen to get one ton of rice product. Naturally, N uptake increases with the increase in yield.
Atanasiu and Samy (1983) classified the varieties according to their nitrogen requirement as follows:
a) High-yielding japonica or bred indica varieties need nitrogen at doses up to 18 kg/da.
b) Low-yielding old or traditional varieties can be grown in soil or with a nitrogen dose of 3-5 kg/da.
c) Late varieties that mature in 150-160 days need more nitrogen than early varieties that mature in 100-120 days.
As a result of the N fertilizer experiments carried out in Trakya Agricultural Research Institute, it was seen that the varieties grown in our country reached the optimum yield with 17-18 kg/da nitrogen.
Type of Nitrogen Fertilizer to be Used
Ammonium-formed nitrogenous fertilizers should be used in order to keep the nitrogen loss at minimum level by denitrification and evaporation in paddy cultivation done by leaving the soil under water. The most suitable nitrogen fertilizers for this are ammonium sulfate and urea (Hill, 1992).
Grist (1975) stated that young plants respond better to NH 4 and older plants to NO - 3 . In a study by Tanaka et al., (1959), when plants fertilized with NH 4 until the cluster formation stage and with NO - 3 in the following stages , they achieved better growth and higher yield in soil solution.
In the studies carried out in Thrace Agricultural Research Institute in 1984, 1985 and 1986, the highest yield was obtained with ammonium sulfate, as seen in Table 1 . It was followed by urea. This shows us that the most suitable N fertilizer to be used in rice farming is ammonium sulfate (Surek et al., 1998).
Chart. 1. The results of the nitrogen fertilizer form experiment conducted in Thrace Agricultural Research Institute in 1983, 1985 and 1986 kg/da (Surek et al. 1998).
|Control (without fertilizer)
Nitrogen Application Time
Depending on the physiological development phase, nitrogen should be divided into appropriate portions and applied in parts. At the same time, the nitrogen application time varies according to the soil structure and irrigation methods. In light soils, it should be applied in more parts to minimize nitrogen loss. In addition, one or two applications may be sufficient on heavy soils.
Rice plant needs a significant amount of nitrogen from the beginning of tillering to the middle of tillering in order to maximize the number of clusters. Nitrogen applied at the beginning of the cluster formation period increases the number of grains in the cluster. Some nitrogen may also be needed in the grain filling cycle (De Datta, 1981).
As a result of a study carried out in Thrace Agricultural Research Institute in 1983, 1984 and 1985, it was observed that the applied nitrogen by dividing it into two or three equal parts and applying it in portions was effective in utilizing nitrogen (Surek et al., 2001). Nitrogen application, the nitrogen to be applied is divided into three equal parts, 1/3 of it is in the soil before planting, 1/3 is at the beginning of tillering and the remaining 1/3 is at the beginning of the cluster formation period (55 or 60 days after planting). The best results were obtained when applied. However, the most critical application time has emerged as the beginning of the cluster formation phase. Nitrogen applied in this period is very important for high yield.
FERTILIZATION WITH PHOSPHORUS
Phosphorus promotes activities such as tillering, root development, early flowering and grain filling in low temperature conditions. Phosphorus is especially needed in the early stages of development. In cases where the amount of usable phosphorus in the soil is insufficient, phosphorus fertilization is very important for proper root development.
In areas where phosphorus is needed, mixing the appropriate amount of phosphorus fertilizer into the soil before planting increases the yield of rice. However, in some fields where rice is planted on top of each other, there is enough phosphorus that can be used by the plant (Hill, 1992).
De Datta (1981) explained the changes brought about by phosphorus in plant development as follows.
- The effect of phosphorus application;
- Increases root development
- It encourages early flowering and grain filling especially in cool climate conditions,
- Increases tillering and grain development,
- Symptoms caused by phosphorus deficiency;
– Formation of short plants with few siblings,
– Formation of narrow, short, upright and dark green leaves,
– Young leaves are healthier than old leaves that turn brown and die later,
– The number of leaves, the number of grains in clusters and clusters decreases,
– Stems are thin and plant development is delayed,
– Maturation is delayed,
– Thousand grain weight and grain quality decrease
– There is a decrease in response to the applied N,
– Algae does not form on the water surface.
As soon as the field is flooded, the usefulness of phosphorus in the soil decreases and the need for phosphorus in the early development stages of rice is very high. For this, it will be very useful to apply all the phosphorus to be applied to the soil before planting for good root development and plant structure formation (Braun and Roy, 1985).
In general, although it varies according to soil characteristics, the amount of phosphorus to be applied is between 6-8 kg/da in rice farming. As phosphorus fertilizer, it can be used between 25-30 kg/da, 20-20-0, or between 30-35 kg, 15-15-15 compound fertilizers or, specially developed by some companies for paddy products and containing three main nutrients. .
FERTILIZATION WITH POTASSIUM
Potash increases leaf area and leaf chlorophyll content, delays leaf death, resulting in wider vegetation formation for photosynthesis and better crop growth. Potash also increases the 1000 grain weight with the number of spikelets and full grains in the cluster. In addition, potash increases the tolerance of the rice plant to bad weather conditions, lodging, diseases and pests.
Symptoms caused by potassium deficiency;
In severe potash deficiency peaks, leaf tips are yellowish brown. Symptoms first appear on older leaves, then extend to the leaf margins and finally reach the leaf base. Upper leaves are short, low structure and dirty green. Older leaves turn from yellow to brown. If potash deficiency is not corrected, discoloration can also be seen on young leaves over time. In addition, in the case of potash deficiency, conditions such as shortening of plants, increased lodging, early leaf death, increased spikelet sterility and unhealthy root development may occur.
In general, our soils are rich in potassium. For this reason, there is no need to use potassium fertilizers in paddy fertilization. However, sometimes there may be a lack of potash in fields where paddy is planted or heavily leveled. In this case, it would be appropriate to use some potash fertilizer at intervals of 2 or 3 years, depending on the need, for high and quality yields. In cases of potash deficiency, product quality and effective utilization of nitrogen fertilizers are reduced. As a source of potash, 15-15-15 compound fertilizers between 30-35 kg or compound fertilizers developed by some companies and containing three main nutrients can be used for paddy products.