Enhancing Soil Organic Carbon through Tank Silt Application

R. AdhinarayananDHAN Foundation

Climate Change and Soil Health

Climate change poses threat tomonsoon dependent rainfedfarming worldwide. Increased dryspell often pushes them to re-sowfailed crops. Indiscriminate use ofchemical fertilizers changed thesoil nutrient composition andphysical properties (hardening oftop soil). It prevents the soil fromabsorbing rain water, and in-turnsurface runoff during rainfallerodes the top soil. The reductionof soil organic matter and moistureholding capacity also increases therisk of rainfed farming andincreases the cost of cultivation,leading farmers to abstain fromfarming, lose employment and facefood and nutritional insecurity.

Study Area

This farmers participatoryresearch was conducted inT.Kallupatti (77.890 E longitudeand 9.750 N latitude) block ofMadurai district, Tamil Nadu inIndia. People locally classify thesoil type as “pottal” (clay with lessmoisture holding capacity andfertility) and “karisal” (blackcotton soil with high moistureholding capacity).

Tank Silt Application

Tank silt is a fine soil broughtfrom surface runoff duringrainfall from catchment areaalong with crop debris and isdeposited as sediment in thetank water spread area anddecomposed over a period time.This silt is considered to be richin organic matter. The poorphysical, chemical and biologicalproperty of the soil heightens theill effects of climate change,which significantly affects therainfed cropping. The studyfocused on application of tanksilt along with goat penning tochange the physical andnutritional characteristics of soil.Upto 2-3 feet sediment (tank silt)was excavated and transportedand spread in agricultural fieldand incorporated duringploughing. In each acre ofrainfed land 50 cubic metrestank silt was applied for 104farmers (including 73 acres ofpottal land and 31 acres ofkarisal land).

Effect on Organic Carbon

Tank silt has significant amountof organic carbon (0.89) thatchanged the organic carboncontent of soil ranging from 0.03to 0.40. It also increased itsmoisture holding capacity.

Tank silt is a locally available andlow-cost substitute for chemicalfertilizer. It has demonstrated itsefficacy in augmenting adaptationcapacity of rainfed farms toclimate change in the study area.It has proven for multiplebenefits on climate resilientfarming that can be promoted inlarge scale.

Fig. 1: Tank Silt being Applied in Rainfed Land

Effect of Tank Silt Application on Crop Yield

Tab. 1 (a+b): Effect of Silt Application on Soil Organic Carbon

Effect on ElectricalConductivity (EC)

Application of tank silt reducedthe EC from 0.02 to 1.21 dSm-1,which was caused by use of salineground water and excessive use ofinorganic fertilizer.

Effect on Crop Yield

Yields of crops such as Barnyardmillet, Maize, Paddy, Pearl-millet,Cotton and Chilly cultivated by theparticipant farmers in the studyarea with (treatment) and withouttank silt (control) application weremeasured and compared with theiraverage normal yields.

Organic Carbon (%)Before After Change

0.29 0.69 0.400.34 0.37 0.030.27 0.36 0.090.2 0.31 0.110.13 0.29 0.160.19 0.31 0.12

Yield (Kg. per acre) Increase of yield (%) compared with

Crop Control Normal Treatment Normal Control

Barnyard millet 100 700 1400 100.00 1300.00

Maize 909 1400 1067 -23.78 17.38

Paddy 2448 2880 3500 21.52 42.97Pearl millet 328 600 417 -30.50 27.13

Cotton 70 350 222 -36.57 217.14

Chilly 100 650 625 -3.84 525.00

0.24

0.39

Before After

Organic Carbon (%)

INTRODUCTION OBJECTIVES MAIN RESULTS

Fig 2: Increased crop yield

CONCLUSION

Fig. 3: Tank Silt

Tab. 2: Effects of tank silt application on crop yield