EFFECT OF RICE STRAW COMPOST ON SOIL MICROBIOLOGICAL PROPERTIES AND YIELD OF RICE

Indian J. Agric. Res., 43 (4) : 263-268, 2009 AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com / indianjournals.com EFFECT OF RICE STRAW COMPOST ON SOIL MICROBIOLOGICAL PROPERTIES AND YIELD OF RICE Sneh Goyal, Dalel Singh*, Sunita Suneja and K.K. Kapoor Department of Microbiology, CCS Haryana Agricultural University Hisar-125 004, India Abstract Utilization of rice straw through composting and its effect on yield of rice was studied. The application of rice straw compost @ 5 t/ha along with half of the recommended dose of inorganic fertilizer increased the microbial biomass C from 136 to 258 mg/ kg soil, dehydrogenase activity from 66 to 118 mg TPF/kg soil/ 24h and alkaline phosphatase from 370 to 680 mg PNP/kg soil/ h. It also resulted in the build up of soil organic C and N from 0.471 and 0.039% to 0.545 and 0.064 % respectively. Carbon and N mineralization rates were also higher than control and soils receiving recommended dose of inorganic fertilizers. The three years grain and straw yield of rice (Basmati and CSR-30) was comparable to the recommended dose of inorganic fertilizers. Key words: compost, Soil microbiological properties, Rice yield. INTRODUCTION Most tropical soils are poor in organic matter due to high rate of turnover and repeated cultivation. Recycling of organic wastes in agriculture is much needed and returns organic matter into the soils. In the Indo-Gangetic plains about 95 million tons of rice residues are produced which is about 39% of total crop residues generated (Sidhu et al., 2003). In Haryana about 6 million tons of rice straw is produced annually, out of which about 63% is burnt. Disposal of straw of high yielding varieties of rice is a problem. Burning has been traditionally used to dispose off crop residues. Burning of rice straw is known to induce environmental and health problems (Jacob et al., 1997; Reinhardt et al., 2001). Rice residue management through incorporation of rice straw is associated with certain problems such as, immobilization of plant nutrients particularly nitrogen, residues impede seed bed preparation and contribute to reduced germination of subsequent crops. Composting arises as a safe option which results in reusability of the nutrients contained in the residue. Production of compost from straw is an alternative to burning and direct incorporation in soil. The management of rice straw through composting will avoid air pollution caused by residue burning as well as loss of plant nutrients and organic matter. There is a need to utilize rice straw as a source of plant nutrients and organic matter to improve soil productivity. The present study was carried out with the objective of utilization of rice residue through composting and its use in agricultural soils as source of important plant nutrients and its effect on soil microbiological properties and yield of rice. MATERIAL AND METHODS composting: Manually harvested rice straw was collected from the * Regional Research Station (CCS HAU), Kaul- 136 021, Haryana, India.

264 INDIAN JOURNAL OF AGRICULTURAL RESEARCH previous crops of rice and was stacked as a windrow (1m x 1m x 10m) after soaking in water containing urea @ 1g/l to adjust C:N ratio to 50:1 and was inoculated with fungal inoculum of Aspergillus awamorii (1g/100 ml) and was covered with polythene sheet to conserve moisture. Moisture was maintained to 60% water holding capacity (WHC) by analyzing the moisture content time to time and adding water at different intervals of composting. The material was allowed to decompose for three months and two turnings were given at 15 and 45 days. The composted rice straw had C/ N ratio 16.2.The composted rice straw was applied in the fields at RRS, Kaul, CCS HAU, Hisar alone or along with inorganic fertilizers and there were following treatments: T1: Control T2: Compost (5t /ha) T3: Inorganic fertilizer (N60 P 2 O 5 30K 2 O ZnSO 4 25 kg /ha) T4: Compost (5t /ha) + Inorganic fertilizer (Same as T3) T5: Compost (5t /ha) + N 60 kg /ha T6: Compost (5t /ha) + N 30 kg /ha Experimental Design: The experimental area lies approximately at 29.6 51 North latitude and 76 40 East longitude and at altitude of 266 m above mean sea level. Soils are mixed hyperthermic Typic Ustocrept. The soil of the area was clay loam. For each treatment there were three plots of size of 50 m 2 and experiment was planned in a randomized design and above treatments were employed. The composted rice straw was added at the rate of 5 t/ ha.nitrogen was added in the form of urea and P was supplied as single super phosphate at different rates depending upon the treatments. Two varieties of rice (Basmati and CSR-30) were grown for three years and rice straw compost was applied to rice 15 days before transplanting in two split doses. Soil sampling: Soils (0-15 cm) from each replicate of treatment were sampled in April 2005 after the harvest of wheat crop from 10 different locations in each plot and pooled together and analyzed in the Department of Microbiology, CCS HAU, Hisar... The soil samples were sieved through 2 mm sieve and adjusted to 40 % water holding capacity and pre-incubated for 7 days to allow microbial activities to settle down after initial disturbances. Other portions of soils were air dried and ground for chemical analysis. Chemical analysis of soil: Soil ph and EC were determined in suspension of air dried soil using 1:2 ratio of soil to water using ph and electrical conductivity meter respectively. Soil organic C was measured by the dichromate digestion method (Kalembassa and Jenkinson, 1973).Total N was measured by Kjeldahl steam distillation method (Bremner, 1965), ammoniacal and nitrate nitrogen by method of Keeney and Bremner (1965) and available P was measured by the method as described by John (1970). Carbon and nitrogen mineralization: Carbon mineralization was determined by the method of Pramer and Schmidt (1984) with slight modification. One hundred gram soil was placed in 500 ml Erlenmeyer flask and 10 ml of 1N NaOH was kept inside each flask to absorb CO 2 evolved from soil. Flasks were stoppered with rubber corks, sealed with paraffin wax and incubated at 30 C. The CO 2 evolved at different intervals was estimated and mineralization of carbon was calculated. Microbial biomass carbon: Soil microbial biomass carbon was estimated by the chloroform fumigation extraction method (Vance et al., 1987). Biomass C was calculated by the following formula: Biomass C = 2.64 [extractable C in fumigated soil - extractable C in unfumigated soil]

Vol. 43, No. 4, 2009 265 Table 1: Soil chemical properties after three years of application of rice straw compost alone or along with inorganic fertilizers Treatments ph EC(dS/ m-) Organic C(%) Total N(%) Mineral N Available P (NH+4-N + NO-3-N) (mg/ kg soil) (mg/ kg soil) Control 7.6 0.64 0.471 0.039 6.2 4.8 Compost (5t /ha) 7.7 0.67 0523 0.064 12.2 6.5 Recommended dose of fertilizer 7.6 0.62 0.485 0.041 7.6 5.2 Compost (5t / ha) + recommended 7.6 0.65 0.545 0.062 11.9 6.8 dose of fertilizer Compost (5t/ha) + N60 kg/ha 7.5 0.65 0.528 0.059 10.6. 6.2 Compost (5t / ha) + N30 kg/ ha 7.6 0.62 0.551 0.058 10.4 6.2 LSD (P=0.05) NS NS 0.01 0.01 2.1 1.3 Enzyme activities: Soil dehydrogenase activity was determined by method of Casida et al. (1964) by 2,3,5 triphenyl tetrazolium chloride reduction and Alkaline phosphatase activity was measured by the method of Tabatabai and Bremner (1969). RESULTS AND DISCUSSION The application of rice straw compost alone or along with inorganic fertilizers did not affect ph and EC of the soil (Table1). This was due to the high buffering capacity of the experimental soil. However the three year continuous additions of rice straw compost alone or along with inorganic fertilizers resulted in increase in organic C contents of the soil from 0.471 to 0.551 %. Total N contents of the soil also increased from 0.039 to 0.064%. Increase in soil organic C with the application of inorganic fertilizers alone is attributed to the better plant growth resulting in more above and below ground plant biomass. The above ground plant biomass was removed however the below ground plant biomass increased the soil organic C from 0.471 to 0.551% in three years of experiments. Similar observations have also been made by Goyal et al.(1992). The increase in organic C in treatments receiving rice straw compost alone or along with inorganic fertilizers is also due to the input of organic matter in the form of rice straw compost (Rickman et al., 2002; Cerri et al., 2003; Dhull et al., 2004). Available P contents were also more with rice straw compost additions than inorganic fertilizers alone. It increased from 4.8 mg/ kg soil to 6.8 mg/ kg soil. Application of rice straw compost o improved micro biological properties of soils which is indicated by the increase in microbial biomass C from 136 mg/ kg soil to 258 mg/ kg soil. The microbial biomass C as percentage of soil organic C increased with rice straw compost additions alone or along with inorganic fertilizers. Microbial biomass C generally comprises about 1-5% of soil organic C (Jenkinson and Ladd,1981) in the present study also it varied from 2.9 to 4.7%.Dehydrogenase activity which is an indicator of total microbial activity also increased from 66 mg triphenyl formazen/ kg soil/ 24h to 118 mg triphenyl formazen/ kg soil/ 24h. Additions of inorganic fertilizers along with rice straw compost had lesser dehydrogenase activity due to the competition of triphenyl tetrazolium chloride with NO 3 - ions for electrons. Alkaline phosphatase activity also increased from 370 mg p-nitrophenol/ kg soil/ h to 680 mg p- nitrophenyl phosphate kg/ soil/ h with the addition of rice straw compost along with inorganic fertilizers. The carbon and nitrogen mineralization potential of the soil which was

266 INDIAN JOURNAL OF AGRICULTURAL RESEARCH Table 2: Changes in soil microbial biomass, soil enzyme activities and C and N mineralization after three years of application of rice straw compost along with inorganic fertilizers Treatments Microbial biomass C (mg/ kg soil) Biomass C as percentage of soil C Dehydrogenase activity (mg TPF/ kg soil /24h) Alkaline phosphatase activity (mg PNP/ kg soil/ h) C mineralization (mg CO 2 -C/ kg soil/ day) N mineralization (mg NH + 4 - NO 3 N/ day) Control 136 2.9 66 370 22.5 2.1 Compost (5t/ha) 232 4.4 133 640 38.4 3.1 Recommended dose 186 3.8 93 590 30.7 5.5 of fertilizer(rdf) Compost (5t/ha) + 4.7 118 680 40.4 5.5 RDF 258 Compost(5t/ha) + 252 4.7 113 540 40.0 4.1 N60kg/ha Compost(5t/ha) + 248 4.5 120 520 38.4 3.7 N30 kg/ha LSD (P=0.05) 12-8 22 1.2 0.4 TPF = triphenyl formazen; PNP = p nitro- phenyl phosphate measured by CO 2 evolution and measuring NH 4 ++ NO 3 - - N up to 28 days increased from 22.5 to 40.4 mg CO 2 -C/ kg soil/ day with the application of rice straw compost along with inorganic fertilizers. Rate of N mineralization also increased with rice straw compost amendment from 2.1 to 5.5 mg NH 4 +- NO 3 - N/ day alone or along with inorganic fertilizers. The mineralization of C which was measured by CO 2 evolution at different intervals and is expressed as cumulative CO 2 C evolution is shown in (Fig.1). The CO 2 evolution was faster in first 21 days and than declined in all the soils treated with rice straw compost alone or along with inorganic fertilizers. As the carbon mineralization takes place other nutrients which are bound to organic matter are released in to the system and are available to the crop. The nitrogen mineralization potential of soil which is indicated by the mineral form of N (NH 4 +-NO- 3 -N) also increased with rice straw compost additions. Organic form of N which is present in form of macromolecules get mineralized slowly to inorganic form which is taken up by the plants was higher in soils amended with rice straw compost alone or along with inorganic fertilizers. Table 3: Effect of paddy straw compost and inorganic fertilizers on grain and straw yield (q/ha) of different rice cultivars. Treatments Rice Taraori Basmati(q/ ha) CSR-30(q/ ha) Grain Straw Grain Straw Control 24.63 32.25 21.63 30.25 Compost (5t /ha) 35.00 48.00 30.50 44.50 Recommended dose fertilizer 43.63 104.7 35.88 90.50 Compost (5t / ha) + RDF 33.25 97.50 27.75 83.75 Compost(5t/ha) + N60kg/ha 33.38 93.25 26.25 79.00 Compost(5t/ha) + N30 kg/ha 37.63 93.25 35.00 91.00 C.D. (P=0.05) Cultivar 1.32 (3.20) Treatment 2.28 (5.54) Cultivar treatment = NS (7.34)

Vol. 43, No. 4, 2009 267 CO 2 -C evolved (mg kg -1 soil) 1200 1000 800 600 400 200 0 0 7 14 21 28 Incubation period in weeks control Compost RDF compost + RDF compost + N60 compost + N30 Fig. 1. Cumulative carbon mineralization in soils amended with rice straw compost alone or along with inorganic fertilizers The average three years yield of rice (Basmati and CSR-30) is shown in Table 3. The grain and straw yield of cultivar CSR-30 and Basmati increased with the application of recommended dose of fertilizers or rice straw compost alone or in combination with rice straw compost. The increase in grain and straw yield of CSR-30 and Basmati was 41 and 42% and 47 and 49% respectively. Among both the varieties, higher yield was observed with basmati compared to CSR 30. Among the different treatments, grain and straw yield of rice was at par where 5t/ ha compost + recommended dose of fertilizers and 5 t/ ha compost + recommended N (N 60 ) were applied. However, highest yield was obtained where only recommended fertilizers were applied. The addition of half dose of nitrogen along with compost also resulted in increase in grain and straw yield of rice over the control or in the soils amended with rice straw compost alone. The grain and straw yield of rice also increased with inorganic fertilizers alone or along with organic residues in the form of rice straw compost significantly due to an overall improvement in the chemical and biological properties of the soil. Utilization of rice straw through composting and its application in agricultural soils is one of the options for straw disposal. Burning of rice straw in situ is easy and convenient and can remove some of plant pathogens but it is not recommended as level of soil organic matter goes down. Incorporation of rice straw directly to soil will cause immobilization of nutrients. Maintenance of soil fertility and productivity is the need of the day as level of soil organic matter is going down due to injudicious use of inorganic fertilizers. There is evidence that use of organic amendments in the form of crop residues, FYM or compost increases the soil organic matter (Mahmood et al., 1997; Graham et al., 2002; Goyal et al., 2006). Microbial biomass which is responsible for carrying out the cycling of important plant nutrients increases or decreases in response to C inputs through organic amendments and is closely related to the amount of soil organic matter (Gregorich et al., 1996; Simek et al.,

268 INDIAN JOURNAL OF AGRICULTURAL RESEARCH 1999; Jedidi et al., 2004; Banerjee et al., 2006). The increase in microbial biomass C, dehydrogenase and phosphatase activities and C and N mineralization rate indicates the accumulation of labile pool of C and N with the application of rice straw compost alone or along with inorganic fertilizers. The use of rice straw compost alone or along with inorganic fertilizers had more positive effects on the buildup of soil organic matter level, microbial biomass and various activities. These improvements in organic matter and microbial activities due to integrated use of rice straw compost along with inorganic fertilizers is the best option left over the burning, removal or direct incorporation of rice straw in the agricultural soils. Under tropical soils the requirement for inorganic fertilizers is high which results in giving high yields of crops but the build up of organic C or nitrogen is low resulting in the poor fertility of agricultural soils. We also could found that addition of organic residues alone or along with inorganic fertilizers give comparable crop yield. CONCLUSIONS The composting of rice straw and its utilization in agricultural soils along with different doses of inorganic fertilizers is beneficial for maintaining soil organic matter level and microbiological properties. Composting of rice straw and its application along with inorganic fertilizers will reduce the cost of farming and will improve soil health by increasing C and N pool of the soils. REFERENCES Banerjee B. et al.(2006). Enviro. Monit. Assess.119:173-189. Bremner, J. M. (1965). In : Methods of Soil Analysis, Part 2 (Black, C. A. et al. eds.) American Society of Agronomy, Madison, Wisconsin. pp. 1177-1237. Casida L.E. Jr et al. (1964). Soil Sci. 98: 371-378. Cerri, C.E. et al. (2003). Environ. Manage. 37: 175-187. Dhull, S. K. et al. (2004). Arch. Agron. Soil Sci. 50: 641-647. Goyal, S. et al. (1992). Soil Biol. Biochem. 24: 1081-1084. Goyal, S. et al. (2006). Arch. Agron. Soil Sci. 52: 617-625. Graham, M. H. et al. (2002). Soil Biol. Biochem. 34: 93-102. Gregorich, E.G. et al. (1996). Soil Sci. Soc. Am. J. 60: 472-476. Insam, H. et al. (1991). Soil Biol. Biochem. 23: 459-464. Jacob, J. et al.(1997). Environ. Health Perspect. 105: 980-985. Jedidi, N. et al. (2004). Waste Manag. Res. 22: 93-99. Jenkinson, D. S. and Ladd, J. N. (1981). In: Microbial Biomass in Soil (Paul, E.A. Ladd, J. M. eds.) Soil Biochemistry, Vol. 5. Dekker New York: pp. 415-471. John, M. K. (1970). Soil Sci. 109: 214-220. Kalembassa, S.J. and Jenkinson, D. S. (1973). J. Sci. Food Agric. 24: 1089-1090. Keeney, D.R. and Bremner, J. M. (1965). Agron. J. 58: 498-503. Mahmood, T. et al. (1997). Biol. Fertil. Soils. 25: 63-68. Olsen s, S. R. et al. (1954). USDA Circ. 939. Washington, D. C. Pramer, C. and Schmidt, A. (1984). In: Methods of Soil Analysis, Part 2 (Black, C. A. eds.) American Society of. Agronomy, Madison. Pp 1395-1397. Reinhardt, T.E. et al. (2001). J Air Waste Manag. Assoc. 51: 443-450. Rickman, R. et al. (2002). Environ Pollu.t 116: 405-411. Sidhu, B. S. et al. (2003). In: Recycling of Rural and Urban Wastes. Department of Soils, Punjab Agricultural University, Ludhiana. pp. 1-35. Simck, M. et al.(1999). Biol. Fertil. Soils. 29: 300-308. Tabatabai, M. A. and Bremner, J. M. (1969). Soil Biol. Biochem. 1: 301-307. Vance, E. D. et al. (1987). Soil Biol. Biochem. 19: 703-707.