Indian J. Agric. Res., 43 (4) : 263 - 268, 2009 AGRICULTURAL RESEARCH COMMUNICATION CENTREwww.arccjournals.com / indianjournals.com

EFFECT OF RICE STRAW COMPOST ON SOIL MICROBIOLOGICALPROPERTIES AND YIELD OF RICE

Sneh Goyal, Dalel Singh*, Sunita Suneja and K.K. KapoorDepartment of Microbiology,

CCS Haryana Agricultural University Hisar-125 004, India

AbstractUtilization 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 therecommended dose of inorganic fertilizer increased the microbial biomass C from136 to 258 mg/ kg soil, dehydrogenase activity from 66 to 118 mg TPF/kg soil/ 24hand alkaline phosphatase from 370 to 680 mg PNP/kg soil/ h. It also resulted in thebuild 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 andsoils receiving recommended dose of inorganic fertilizers. The three years grain andstraw yield of rice (Basmati and CSR-30) was comparable to the recommended doseof inorganic fertilizers .

Key words: Rice straw compost, Soil microbiological properties, Rice yield.

INTRODUCTIONMost tropical soils are poor in organic

matter due to high rate of turnover and repeatedcultivation. Recycling of organic wastes inagriculture is much needed and returns organicmatter into the soils. In the Indo-Gangeticplains about 95 million tons of rice residuesare produced which is about 39% of total cropresidues generated (Sidhu et al., 2003). InHaryana about 6 million tons of rice straw isproduced annually, out of which about 63%is burnt. Disposal of straw of high yieldingvarieties of rice is a problem. Burning has beentraditionally used to dispose off crop residues.Burning of rice straw is known to induceenvironmental and health problems (Jacob etal., 1997; Reinhardt et al., 2001). Rice residuemanagement through incorporation of ricestraw is associated with certain problems suchas, immobilization of plant nutrientsparticularly nitrogen, residues impede seed bed

preparation and contribute to reducedgermination of subsequent crops. Compostingarises as a safe option which results inreusability of the nutrients contained in theresidue. Production of compost from straw isan alternative to burning and directincorporation in soil. The management of ricestraw through composting will avoid airpollution caused by residue burning as well asloss of plant nutrients and organic matter. Thereis a need to utilize rice straw as a source ofplant nutrients and organic matter to improvesoil productivity. The present study was carriedout with the objective of utilization of riceresidue through composting and its use inagricultural soils as source of important plantnutrients and its effect on soil microbiologicalproperties and yield of rice.

MATERIAL AND METHODSRice straw 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 awindrow (1m x 1m x 10m) after soaking inwater containing urea @ 1g/l to adjust C:Nratio to 50:1 and was inoculated with fungalinoculum of Aspergillus awamorii (1g/100 ml)and was covered with polythene sheet toconserve moisture. Moisture was maintainedto 60% water holding capacity (WHC) byanalyzing the moisture content time to timeand adding water at different intervals ofcomposting. The material was allowed todecompose for three months and two turningswere given at 15 and 45 days. The compostedrice straw had C/ N ratio 16.2.The compostedrice straw was applied in the fields at RRS,Kaul, CCS HAU, Hisar alone or along withinorganic fertilizers and there were followingtreatments:

T1: ControlT2: Compost (5t /ha)T3: Inorganic fertilizer (N60 P2O530K2OZnSO4 25 kg /ha)T4: Compost (5t /ha) + Inorganic fertilizer(Same as T3)T5: Compost (5t /ha) + N60 kg /haT6: Compost (5t /ha) + N30 kg /ha

Experimental Design: The experimental arealies approximately at 29.6 51’ North latitudeand 76 40’ East longitude and at altitude of266 m above mean sea level. Soils are mixedhyperthermic Typic Ustocrept. The soil of thearea was clay loam. For each treatment therewere three plots of size of 50 m2 andexperiment was planned in a randomizeddesign and above treatments were employed.The composted rice straw was added at the rateof 5 t/ ha .Nitrogen was added in the form ofurea and P was supplied as single superphosphate at different rates depending upon thetreatments. Two varieties of rice (Basmati andCSR-30) were grown for three years and ricestraw compost was applied to rice 15 days beforetransplanting in two split doses.

Soil sampling: Soils (0-15 cm) from eachreplicate of treatment were sampled in April2005 after the harvest of wheat crop from 10different locations in each plot and pooledtogether and analyzed in the Department ofMicrobiology, CCS HAU, Hisar... The soilsamples were sieved through 2 mm sieve andadjusted to 40 % water holding capacity andpre-incubated for 7 days to allow microbialactivities to settle down after initialdisturbances. Other portions of soils were airdried and ground for chemical analysis.

Chemical analysis of soil: Soil pH andEC were determined in suspension of air driedsoil using 1:2 ratio of soil to water using pHand electrical conductivity meter respectively.

Soil organic C was measured by thedichromate digestion method (Kalembassaand Jenkinson, 1973).Total N was measuredby Kjeldahl steam distillation method(Bremner, 1965), ammoniacal and nitratenitrogen by method of Keeney and Bremner(1965) and available P was measured by themethod as described by John (1970).

Carbon and nitrogen mineralization:Carbon mineralization was determined by themethod of Pramer and Schmidt (1984) withslight modification. One hundred gram soilwas placed in 500 ml Erlenmeyer flask and 10ml of 1N NaOH was kept inside each flask toabsorb CO2 evolved from soil. Flasks werestoppered with rubber corks, sealed withparaffin wax and incubated at 30°C. The CO2evolved at different intervals was estimated andmineralization of carbon was calculated.

Microbial biomass carbon: Soil microbialbiomass carbon was estimated by thechloroform–fumigation extraction method(Vance et al., 1987). Biomass C wascalculated by the following formula:

Biomass C = 2.64 [extractable C in fumigatedsoil - extractable C in unfumigated soil]

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Table 1: Soil chemical properties after three years of application of rice straw compost alone or along withinorganic 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 4.8Compost (5t /ha) 7.7 0.67 0523 0.064 12.2 6.5Recommended dose of fertilizer 7.6 0.62 0.485 0.041 7.6 5.2Compost (5t / ha) + recommended 7.6 0.65 0.545 0.062 11.9 6.8dose of fertilizerCompost (5t/ha) + N60 kg/ha 7.5 0.65 0.528 0.059 10.6. 6.2Compost (5t / ha) + N30 kg/ ha 7.6 0.62 0.551 0.058 10.4 6.2LSD (P=0.05) NS NS 0.01 0.01 2.1 1.3

Enzyme activities: Soil dehydrogenaseactivity was determined by method of Casidaet al. (1964) by 2,3,5 triphenyl tetrazoliumchloride reduction and Alkaline phosphataseactivity was measured by the method ofTabatabai and Bremner (1969).

RESULTS AND DISCUSSIONThe application of rice straw compost

alone or along with inorganic fertilizers did notaffect pH and EC of the soil (Table1). This wasdue to the high buffering capacity of theexperimental soil. However the three yearcontinuous additions of rice straw compostalone or along with inorganic fertilizers resultedin increase in organic C contents of the soilfrom 0.471 to 0.551 %. Total N contents ofthe soil also increased from 0.039 to 0.064%.Increase in soil organic C with the applicationof inorganic fertilizers alone is attributed to thebetter plant growth resulting in more aboveand below ground plant biomass. The aboveground plant biomass was removed howeverthe below ground plant biomass increased thesoil organic C from 0.471 to 0.551% in threeyears of experiments. Similar observationshave also been made by Goyal et al.(1992).The increase in organic C in treatmentsreceiving rice straw compost alone or alongwith inorganic fertilizers is also due to the inputof organic matter in the form of rice strawcompost (Rickman et al., 2002; Cerri et al.,

2003; Dhull et al., 2004). Available P contentswere also more with rice straw compostadditions than inorganic fertilizers alone. Itincreased from 4.8 mg/ kg soil to 6.8 mg/ kgsoil.

Application of rice straw compost oimproved micro biological properties of soilswhich is indicated by the increase in microbialbiomass C from 136 mg/ kg soil to 258 mg/ kgsoil. The microbial biomass C as percentageof soil organic C increased with rice strawcompost additions alone or along withinorganic fertilizers. Microbial biomass Cgenerally comprises about 1-5% of soil organicC (Jenkinson and Ladd,1981) in the presentstudy also it varied from 2.9 to 4.7%.Dehydrogenase activity which is an indicatorof total microbial activity also increased from66 mg triphenyl formazen/ kg soil/ 24h to 118mg triphenyl formazen/ kg soil/ 24h. Additionsof inorganic fertilizers along with rice strawcompost had lesser dehydrogenase activity dueto the competition of triphenyl tetrazoliumchloride with NO3- ions for electrons. Alkalinephosphatase activity also increased from 370mg p-nitrophenol/ kg soil/ h to 680 mg p-nitrophenyl phosphate kg/ soil/ h with theaddition of rice straw compost along withinorganic fertilizers.

The carbon and nitrogenmineralization 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 threeyears of application of rice straw compost along with inorganic fertilizers

Control 136 2.9 66 370 22.5 2.1Compost (5t/ha) 232 4.4 133 640 38.4 3.1Recommended dose 186 3.8 93 590 30.7 5.5of fertilizer(RDF)Compost (5t/ha) + 4.7 118 680 40.4 5.5RDF 258Compost(5t/ha) + 252 4.7 113 540 40.0 4.1N60kg/haCompost(5t/ha) + 248 4.5 120 520 38.4 3.7N30 kg/haLSD (P=0.05) 12 - 8 22 1.2 0.4

TPF = triphenyl formazen; PNP = p nitro- phenyl phosphate

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 CO2-C/ kg

soil/ day)

N mineralization

(mg NH4+-

NO3N/ day)

Table 3: Effect of paddy straw compost and inorganic fertilizers on grain and straw yield (q/ha) of differentrice cultivars.

Treatments Rice Taraori Basmati(q/ ha) CSR-30(q/ ha)Grain Straw Grain Straw

Control 24.63 32.25 21.63 30.25Compost (5t /ha) 35.00 48.00 30.50 44.50Recommended dose fertilizer 43.63 104.7 35.88 90.50Compost (5t / ha) + RDF 33.25 97.50 27.75 83.75Compost(5t/ha) + N60kg/ha 33.38 93.25 26.25 79.00Compost(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)

measured by CO2 evolution and measuringNH4++ NO3- - N up to 28 days increasedfrom 22.5 to 40.4 mg CO2-C/ kg soil/ day withthe application of rice straw compost alongwith inorganic fertilizers. Rate of Nmineralization also increased with rice strawcompost amendment from 2.1 to 5.5 mgNH4+- NO3- N/ day alone or along withinorganic fertilizers. The mineralization of Cwhich was measured by CO2 evolution atdifferent intervals and is expressed ascumulative CO2–C evolution is shown in(Fig.1). The CO2 evolution was faster in first21 days and than declined in all the soils

treated with rice straw compost alone or alongwith inorganic fertilizers. As the carbonmineralization takes place other nutrientswhich are bound to organic matter are releasedin to the system and are available to the crop.

The nitrogen mineralization potentialof soil which is indicated by the mineral formof N (NH4+-NO-3-N) also increased with ricestraw compost additions. Organic form of Nwhich is present in form of macromoleculesget mineralized slowly to inorganic form whichis taken up by the plants was higher in soilsamended with rice straw compost alone oralong with inorganic fertilizers.

Vol. 43, No. 4, 2009 267

Fig. 1. Cumulative carbon mineralization in soils amended with rice straw compost alone or along with inorganic fertilizers

0

200

400

600

800

1000

1200

0 7 14 21 28

CO

2 -C

evo

lved

(mg

kg-1

soi

l)control

Rice strawCompost

RDF

Rice strawcompost +RDFRice strawcompost +N60Rice strawcompost +N30

Incubation period in weeks

The average three years yield of rice(Basmati and CSR-30) is shown in Table 3.The grain and straw yield of cultivar CSR-30and Basmati increased with the applicationof recommended dose of fertilizers or ricestraw compost alone or in combination withrice straw compost. The increase in grain andstraw yield of CSR-30 and Basmati was 41and 42% and 47 and 49% respectively. Amongboth the varieties, higher yield was observedwith basmati compared to CSR 30. Amongthe different treatments, grain and straw yieldof rice was at par where 5t/ ha compost +recommended dose of fertilizers and 5 t/ hacompost + recommended N (N60) wereapplied. However, highest yield was obtainedwhere only recommended fertilizers wereapplied. The addition of half dose of nitrogenalong with compost also resulted in increasein grain and straw yield of rice over the controlor in the soils amended with rice straw compostalone. The grain and straw yield of rice alsoincreased with inorganic fertilizers alone oralong with organic residues in the form of ricestraw compost significantly due to an overall

improvement in the chemical and biologicalproperties of the soil.

Utilization of rice straw throughcomposting and its application in agriculturalsoils is one of the options for straw disposal.Burning of rice straw in situ is easy andconvenient and can remove some of plantpathogens but it is not recommended as levelof soil organic matter goes down.Incorporation of rice straw directly to soil willcause immobilization of nutrients.Maintenance of soil fertility and productivityis the need of the day as level of soil organicmatter is going down due to injudicious use ofinorganic fertilizers. There is evidence that useof organic amendments in the form of cropresidues, FYM or compost increases the soilorganic matter (Mahmood et al., 1997;Graham et al., 2002; Goyal et al., 2006).Microbial biomass which is responsible forcarrying out the cycling of important plantnutrients increases or decreases in responseto C inputs through organic amendments andis closely related to the amount of soil organicmatter (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 andC and N mineralization rate indicates theaccumulation of labile pool of C and N withthe application of rice straw compost alone oralong with inorganic fertilizers. The use of ricestraw compost alone or along with inorganicfertilizers had more positive effects on thebuildup of soil organic matter level, microbialbiomass and various activities. Theseimprovements in organic matter and microbialactivities due to integrated use of rice strawcompost along with inorganic fertilizers is thebest option left over the burning, removal ordirect incorporation of rice straw in theagricultural soils. Under tropical soils the

requirement for inorganic fertilizers is highwhich results in giving high yields of crops butthe build up of organic C or nitrogen is lowresulting in the poor fertility of agricultural soils.We also could found that addition of organicresidues alone or along with inorganic fertilizersgive comparable crop yield.

CONCLUSIONSThe composting of rice straw and its

utilization in agricultural soils along withdifferent doses of inorganic fertilizers isbeneficial for maintaining soil organic matterlevel and microbiological properties.Composting of rice straw and its applicationalong with inorganic fertilizers will reduce thecost of farming and will improve soil health byincreasing C and N pool of the soils.

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