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P.MAHESWARAREDDY,G.KRISHNAREDDY,G.PRABHAKARREDDY,K.V.NAGAMADHURI,P.SUDHAKARAND B.RAVINDRAREDDY
Scientist (Agronomy), Agronomy Division, Regional Agricultural Research Station, ANGRAU, Tirupati -517502,Chittoor (Dist.,), Andhra Pradesh.
A field experiment was conducted at farmer’s field located at K.C.Peta village of Tirupati rural mandal of Chittoor district during rabi, 2014-15 to study the effect of nitrogen and phosphorus levels on growth, yield and economics of rice under Mechanized System of Rice intensification (MSRI)in Randomized Block Design with factorial concept with four Nitrogen levels (80, 120, 160 and 200 kg N ha-1) and three phosphorus levels (40, 60 and 80 kg P2O5 ha-1) replicated thrice. Among nitrogen levels, application of 160 and 200 kg N ha-1 recorded comparable yield attributes, yield and net returns. Hence, application of nitrogen @ 160 kg ha-1 was found to be optimum dose under mechanized system of rice intensification. Non significant differences were recorded in grain and straw yields and returns among phosphorus levels and their interaction with nitrogen due to initial soil phosphorus build up. Hence, application of 160 kg N ha-1 coupled with 40 kg P2O5 ha-1 can be recommended for machine transplanted rice for realizing higher yields and returns under mechanized system of rice intensification.
Nitrogen, phosphorus, grain yield, straw yield, economics, MSRI.
Rice is one of the most important cereal crops, which plays a key role for food security and important staple food for more than 50 percent population of the world. About 90 percent of the rice grown in the world is produced and consumed only in Asian countries and it supplies 50 to 80 per cent calories of energy to Asians (Vasudevan et al., 2014). India with highest area under rice crop (44.1 million hectares) is the second largest producer (158 million tonnes) of rice in the world after China (197 million tonnes) but ranks 35th with respect to its productivity. However, India’s rice productivity (2.42 t ha-1) is far below the world’s average productivity of 4.36 t ha-1 (India stat, 2014). In Andhra Pradesh state, rice is the principal food crop cultivated throughout the state in an area of about 2.39 m ha with an annual production of 8.45 m t andproductivity of 3.53 t ha-1 (Statistical Year Book, 2015). In recent years, the area under rice crop is decreasing year by year due to water shortage and rapid
urbanization, but demand for rice is growing every year and it is estimated that by 2025 AD the requirement would be 125 million tonnes (Kumar et al., 2009). To sustain present food self-sufficiency and to meet future food requirements at the current population growth rate of 1.5 %, the rice productivity has to be increased with good management practices under shrinking availability of land and water resources
Historically, rice cultivation is a labour intensive task involving land preparation, transplanting and harvest-ing etc., Manual transplanting of rice is the most common and popular practice being followed under lowland eco-system, which is tedious, laborious, time consuming op-eration involving enormous drudgery and requires about 300-350 man-h/ha, which is roughly 25 per cent of the total labour requirement of paddy cultivation. Labour scar-city during peak period of transplanting and escalating labour cost make the manual transplanting technique more expensive which invariably leads to delay in transplant-ing, resulting in reduction of yield and leads to less profit (Sreenivasulu and Reddy, 2013).
Mechanization increases land and labour productivity by timely completion of farm operations and reduces the drudgery of humans and animals. Mechanization in transplanting through rice transplanter using mat nursery reduces the cost of cultivation since large area can be transplanted within a very short period (Mohanty et al., 2014). Mechanically transplanted rice gave higher benefit cost ratio of 34.46% compared to manually transplanted rice (Mohanty et al., 2010).
Under mechanized system of rice intensification (MSRI), rice crop tends to produce profuse tillering due to planting of relatively younger seedlings at wider spacing. But all the tillers produced are not becoming productive due to less conversion ratio and even the grain filling is poor in tertiary tillers which ultimately causing the reduction in grain yield. This may be attributed to inadequate nutrition and long assigned vegetative period, due to which nutrient hunger is more pronounced than conventional transplanting at recommended dose of nutrients. To avoid this starvation, due importance should be given to nutrient management under mechanized system of rice intensification. Keeping these in view the present experiment was taken up to optimize nitrogen and phosphorus levels for machine transplanted rice under mechanized system of rice intensification (MSRI) for southern zone of Andhra Pradesh.
A field experiment was carried out during rabi2014-15 at farmer’s field at K.C.Peta village of Tirupati mandal of Chittor district situated at an altitude of 182.9 m above mean sea level at 13032’0’’ N latitude and 79o24’25’’ E longitude in Southern agro climatic zone of Andhra Pradesh. The experimental soil was clay loam in texture, slightly alkaline in reaction (7.9), low in organic carbon (0.51) and available nitrogen (216 kg ha-1), high in
The experiment was laid out in Randomized Block Design with factorial concept with four Nitrogen levels (80, 120, 160 and 200 kg N ha-1) and three phosphorus levels (40, 60 and 80 kg P2O5 ha-1) replicated thrice. A common dose of 40 kg K2O ha-1 was applied as basal dose to all the treatments. Entire P was applied basally as per treatment and N was applied in three equal splits at basal, 20 DAT and 40 DAT. Nursery was raised in plastic trays filled with the soil and press mud cake in 70:30 ratio and placed in raised beds. Foliar spray of 13-00-45 @ 0.5% was applied at 10 DAS. Machine transplanting was done at spacing 30 cm x 13-15 cm using 16 days old seedlings of NLR-34449, a medium duration variety with Yanmar VP8Dtransplanter. Individual plots were kept at 5.0 m length x 5.0 m width. Growth parameters, yield attributes, yield and economics were worked out. All the necessary plant protection measures were taken up during the crop growth period.
Growth parameters
Application of 200 kg N ha-1 recorded significant increase in plant height over 80 and 120 kg N ha-1 and was comparable with 160 kg N ha-1. Significantly minimum plant height was recorded with lower level of nitrogen application (80 kg N ha-1) which was at par with 120 kg N ha-1. These results are in consonance with the findings of Dwivedi et al., (2006) and Chamely et al., (2015). Leaf area index of rice is closely related to grain production as it affects the rate of photosynthate production. It appears that plant height, tiller numbers and the aboveground biomass were significantly affected by the leaf area index which varied with the rates of nitrogen application. The rice crop responded well to the application of 200 kg N ha-1 by producing significantly larger leaf area and LAI at all crop growth stages. Application of 200 kg N ha-1 produced significantly larger LAIwhich was however did not vary significantly from the application of 160 kg N ha-1 .As compared to higher levels of nitrogen,
120 kg N ha-1 resulted in significantly lesser LAI. Application of 80 kg N ha-1 recorded significantly lower LAI. Several researchers such as Salem et al., (2011) and Verma et al.(2008) reported increased leaf area index with increasing nitrogen levels.
Application of 200 kg N ha-l recorded maximum dry matter production m-2 which was comparable with 160 kg N ha-l and significantly higher than the application of 120 kg N ha-l and 80 kg N ha-l. Application of 80 kg N ha-l produced significantly lower dry matter production m 2. Application of 160 kg N ha-1 has produced significantly higher dry matter m-2 over the application of 120 and 80 kg N ha-1. The increase in dry matter accumulation is justifiable due to increasing rates of applied mineral N fertilizer. Higher level of N produced higher dry matter production, which is quite acceptable due to supply of enough nutrients to satisfy the demand of the crop. Nitrogen being an important constituent of amino acids and protoplast, directly influences the plant growth and development through better utilization of photosynthates by producing more number of tillers and taller plants owing to adequate supply of nitrogen resulting in higher biomass production in plants. Similar results were reported by Meena et al. (2003).
Phosphorus levels and their interaction with nitrogen could not influence the rice crop significantly with respect to plant height, LAI and dry matter production. These results are in close agreement with the findings of Murthy et al., (2015) who observed comparable growth parameters at higher phosphorus levels but superior over control (without application of phosphorus).
Yield attributes
Yield attributes viz., number of panicles m-2, panicle length, number of filled grains panicle-1 were significantly influenced by N levels.
Application of phosphorus, nitrogen &phosphorus however had a non significant influence on yield attributes. The number of panicle m-2 increased linearly with increasing N levels and application of 200 kg N ha-1 recorded maximum number of panicles m-2 which however, did not vary significantly with 160 kg N ha-1 and superior over lower levels of nitrogen (80 and 120 kg N ha-1). Application of 80 kg N ha-1 recorded significantly lowest number of panicles m-2.
Panicle length varied significantly with levels of nitrogen application and application of 200 kg N ha-1 recorded significantly longest panicle length which was comparable with the application of 160 kg N ha-1 and significantly longer than 120 kg N ha-1 and 80 kg N ha-1. Shortest panicle length was recorded with the application of 80 kg N ha-1 which was at par with 120 and 160 kg N ha-1 .
Increase of nitrogen levels increased the number filled grains panicle-1 and decreased number of chaffy grains panicle-1 and sterility per cent. Application of 200 kg N ha-1 recorded maximum number of filled grains panicle-1 which did not vary significantly with 160 kg N ha-1. Application of 120 kg N ha-1 resulted in significantly lesser number of filled grains panicle-1 as compared to 160 and 200 kg N ha-1 but, comparable with 80 kg N ha-1. Application of 160 kg N ha-1 has recorded significantly more number of filled grains panicle-1 over 120 and 80 kg N ha-1. Phosphorus levels and their inter action with nitrogen has shown non significant response to number of panicle m-2, panicle length and number of filled grains panicle-1.
Yield
Grain and straw yields were significantly increased with increased levels of nitrogen. Maximum grain and straw yields were recorded with the application
of 200 kg N ha-1 which was comparable with 160 kg N ha-1. As compared to higher levels of nitrogen, application
of 120 kg N ha-1 resulted in significantly lower grain and straw yield. Application of 80 kg N ha-1 recorded significantly lower grain and straw yield. In spite of the fact that the rice could not respond to phosphorus application and its interaction with nitrogen due to high initial soil available phosphorus, there was marginal increase in rice grain and straw yield, at higher levels of phosphorus application. Highest grain and straw yield was recorded with the application of 80 kg P2O5 ha-1 which was comparable with 60 kg P2O5 ha-1 and 40 kg P2O5 ha-1
Economics
Highest production cost was observed with higher N and P level and reduced with lower N and P level as it is directly related to the quantity of nitrogen and phosphorus applied in the form of urea and single super phosphate. As the grain and straw yields were significantly increased at higher doses, likewise maximum gross returns, net returns and highest Benefit-Cost (B: C) ratio were realized at 200 kg N ha-1 which remained at par with 160 kg N ha-1 but statistically better returns and B: C ratio over the application of 120 kg N ha-1 and 80 kg N ha-1. Gross returns, net returns and B: C ratio shown non significant differences with phosphorus levels and their interaction with nitrogen levels.
In conclusion, the results revealed that, application of 160 kg N ha-1 and 200 kg N ha-1 recorded comparable growth parameters, yield attributes, yield and net returns, hence, application of nitrogen @ 160 kg ha-1 was found to be optimum dose for realizing higher yields. As phosphorus
levels and their interaction with nitrogen shown non sig-nificant differences in yields and returns due to initial soil phosphorus build up, phosphorus application at lower dose of 40 kg P2O5 ha-1 can be recommended. Hence, applica-tion of 160 kg N ha-1 and 40 kg P2O5 ha-1 can be recom-mended for machine transplanted rice under high soil phos-phorus build up condition for realizing higher yields and returns for Southern agro climatic zone of Andhra Pradesh under mechanized system of rice intensification.
