Browsing by Author "Pramila Aggarwal"
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ThesisItem Open Access Impact of Resource Conservation technologies on soil structural properties in Rai block of Sonepat district of Haryana(IARI, DIVISION OF AGRICULTURAL PHYSICS, 2012) MUKHTAR AHMED; Pramila AggarwalA study was conducted in farmers‘ fields of Rai block of Sonepat district to study the long term impact of two widely adopted resource conservation technologies (RCT‘s) namely bed planting and zero tillage on structural properties of soils of recent alluvial plains of river Yamuna. Vegetables growing bed planted areas mostly had medium texture soils, easy access to market and availability of fresh water. Zero tillage was practiced mainly by farmers to timely sow wheat in fine textured soils and low lying areas where soils do not dry even in mid-November. Aggregate mean weight diameter by dry sieving and wet sieving (DS-MWD and WS-MWD) under different RCT‘s were studied to compare structural condition of the soils under continuous use of these technologies. Other important structural indices such as dispersion ratio (a measure of ease of dispersion) (DR), colloid moisture equivalent ration (a measure of ease of percolation) (CMER), erosion ratio (EI), stability index (SI), clay ratio (CR) were also studied to monitor the susceptibility of soil to erosion. Results revealed that in the surveyed villages under conventional tillage, the average magnitude of DR and ER were 0.58 and 0.82, respectively, and CMER was <1, which indicated the erodible nature of these soils. Analysis of data of bed and conventional systems revealed that on an average, there was 0.07-0.08% increase in OC in bed planted system as compared to conventional system. It was mainly due to fewer disturbances in soil because of reshaping of beds for next two seasons before making fresh beds. Improved soil OC in bed system increased WS-MWD (1.89 mm) as compared to CT (1.57 mm). On the other hand, DS-MWD of bed system was lower than that of CT. Therefore CMWD was lower in beds as compared to CT, which indicated improvement in aggregate stability by adoption of bed planting system. The decrease of DR, ER and CR from 0.66, 0.52 and 4.25under CT to 0.42, 0.28 and 2.38 under beds indicated reduced eroding tendency of these soils under bed planting. Similarly increase in CMER and SI from 0.75 and 20.2 under CT to 1.1 and 34 under bed also indicated improvement in soil structural condition by bed planting. Comparison of soil data of ZT and CT showed improvement in OC, AWC and 28 reduction in BD and PR under ZT as compared to CT. Improved soil OC in ZT increased WS-MWD (mm) as compared to CT (mm). The decrease of DR, ER and CR from 0.74, 0.63 and 5.99 under CT to 0.6, 0.46 and 3.8 under ZT indicated improved aggregation under zero tillage. Similarly increase in CMER and SI from 0.66 and 9.21 under CT to 0.7 and 20.4 under ZT also indicated improved soil structural condition by adoption of zero tillage. Thus in nutshell it was concluded that by adopting suitable RCT‘s soil carbon and aggregation were improved and soils became more resistant to erosion.ThesisItem Open Access INTEGRATED NUTRIENT MANAGEMENT EFFECT ON AGGREGATE TURNOVER AND C STABILITY IN A SANDY LOAM SOIL UNDER A RICE-WHEAT CROPPING SYSTEM(IARI, DIVISION OF AGRICULTURAL PHYSICS, 2012) BAPPA DAS; Pramila AggarwalThe present study aims in understanding the impacts of integrated nutrient management practices on the mechanical properties of aggregates and structural stability of a sandy loam soil. Soil samples were collected from a long-term experiment at PDFSR, Modipuram from 0-7.5, 7.5-15 and 15-30 cm layers and tensile strength (TS), aggregate density (agg), moisture retention by aggregates (AMR) at field capacity and wilting point, and water stability of aggregates were monitored. Soil bulk density and water holding capacity was also recorded. The treatments included unfertlization in both rice and wheat (T1) as control; NPK+Zn in rice and NPK in wheat (T2); NPK+Zn+S in rice & NPK in wheat (T3); N(75)PK+25N (FYM) in rice & NPK in wheat (T4); N(75)PK+25N (Sulphitation press mud) in rice & NPK in wheat (T5); N(75)PK+25N (Green gram residue) in rice & NPK in wheat (T6); N(75)PK + 25N (Green gram residue) in rice and N(75)PK+25N (FYM) in wheat (T7); N(75)PK+25N (Crop Residue) in both crops (T8). The TS and agg were lower with organic substitution (P<0.05) while AMR at field capacity was 1-2% higher with organic inputs. Aggregate properties were largely improved by crop residue addition, and the effect was similar to green manuring (rice) and FYM (wheat) combination. Aggregates of 5-8 mm size from T8 had the lowest TS (0.79 kPa at 0-7.5 and 0.81 kPa at 7.5-15 cm layers) and agg (1.60 Mg m-3 at 0-7.5 and 1.65 Mg m-3 at 7.5-15 cm layers), but the highest AMR at field capacity (25.2 and 22.2% at 0-7.5 and 7.5-15 cm layers). Mean agg was higher than soil bulk density and the ratio of the two can be used as useful indicator of soil structural improvement. Macroaggregates (>0.25 mm) constituted 58-92% of water-stable aggregates (WSA), although the proportion significantly varied among the treatments and the depths of soil. Treatment T8 had 83-92% water stable macro-aggregates, significantly higher than other aggregates sizes. Aggregation indices showed better structural stability with crop residue and manure application. Long-term (>18 yr) integrated nutrient management with partial 29 substitution of N by organics improved the aggregates properties compared with mineral fertilizer application in rice-wheat rotation.ThesisItem Open Access MODELING SOIL HYDROTHERMAL DYNAMICS, ROOT WATER UPTAKE AND RADIATION USE IN PIGEON PEA UNDER CONSERVATION AGRICULTURE(DIVISION OF AGRICULTURAL PHYSICS INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI, 2017) VIKAS KUMAR RAI; Pramila AggarwalThe studies on effect of conservation agricultural practices on moderation of soil temperature and distribution of soil water in the profile during crop growth need special attention for understand changes in water and energy balance components, which are crucial components of crop improvement programmes. In current study, both water balance and energy balance components of soil under different conservation agriculture (CA) practices were analyzed using the Hydrus-2D model during the pigeonpea growth. The treatments were: conventional tillage (CT), zero tillage (ZT), permanent narrow beds (PNB), permanent broad beds (PBB), ZT with residue (ZT+R), PNB with residue (PNB+R) and PBB with residue (PBB+R). Results on soil physical environment changes after 7 years of continuous adoption of different CA practices showed that both permanent broad bed and narrow bed with and without residue retention and zero tillage with residue retention reduced bulk density (BD), increased field saturated hydraulic conductivity (Ksat) and improved soil water retention significantly over CT. Ksat values obtained as the output of Rosetta Lite model could not be used as hydraulic input parameter as they were very low and hence, measured value of Ksat and α and n parameter obtained as output of Rosetta Lite model were optimized through inverse modeling and were used as hydraulic inputs of the model which predicted daily change in SWC of profile with reasonable accuracy (R2= 0.78; RMSE= 0.012). Soil water balance simulated from the model showed higher cumulative transpiration, lower cumulative evaporation and higher soil water retention in most of the CA practices as compared to CT. Computed values of Thermal conductivity (λ) obtained from observed soil temperature (ST) data at different soil water contents showed good correlation with the optimized values of thermal conductivity obtained through inverse modeling. Hydrus 2D predicted ST variation of 0-20 cm soil profile using optimized values with reasonable accuracy (R2=0.91) for a simulation period of 10 days, although it slightly over predicted ST values. Both observed and simulated results of ST as function of depth and time, revealed that fluctuation of peak magnitude of temperature wave between 5 and 20 cm was more in 138 CT than in PBB+R. Simulated Value of ST at hourly interval for 5 cm depth showed more variation and occurrence of peak was 2-3 hours earlier than those of ST values at 15 and 20 cm. Among different energy balance components, computed ground heat flux was lower and Latent heat flux was more in PBB+R as compared to CT. Hence it was concluded that PBB+R and PNB+R practices should be adopted for pigeon pea cultivation, as these practices modified soil hydrothermal regimes, enhanced root growth and improved radiation interception, LAI and biomass production. The Hydrus-2D can satisfactorily simulate the temporal changes in water balance components as well as ground heat flux (G) and latent heat flux (LE) components of energy balance during the crop period; hence it may be adopted for evaluating different management practices in terms of improvement in water and radiation use by them.ThesisItem Open Access Modeling temporal distribution of water, ammonium-N and nitrate-N in root zone of wheat using HYDRUS 2D under conservation agriculture(DIVISION OF AGRICULTURAL PHYSICS ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI -, 2018) MOHAMMED SHAFEEQ P M; Pramila AggarwalThe studies on effect of conservation agricultural practices in improving the soil water and soil nitrogen distribution in root zone during crop growth need special attention as these are crucial components of irrigation and fertilizer management programmes. In current study, temporal distribution of both soil water and soil NO3-N under different conservation agriculture (CA) practices were analyzed using the Hydrus-2D model during the wheat growth. The treatments were: conventional tillage (CT), zero tillage (ZT), permanent broad beds (PBB), ZT with residue (ZT+R), and PBB with residue (PBB+R). Results on soil physical environment changes after 8 years of continuous adoption of these practices showed that permanent broad bed with and without residue retention and zero tillage with residue retention reduced subsurface bulk density (BD), increased field saturated hydraulic conductivity (Kfs) and improved soil water retention significantly over CT. Measured value of Kfs and Į and n parameter obtained as output of Rosetta Lite model were optimized through inverse modeling and were used as hydraulic inputs of the model which predicted daily change in SWC of profile with reasonable accuracy (R2 = 0.75; RMSE= 0.038). Soil water balance simulated during 62-91 DAS from the model showed 50% higher cumulative transpiration and 50% lower cumulative drainage and higher soil water retention in PBB+R as compared to CT. Reported values of first-order rate constants representing nitrification of urea to NH4(ȝa )(dѸ1 )and representing nitrification of NH4-N to NO3-N (ȝn) (dѸ1 ) and the distribution coefficient of urea (Kd - in cm3 mgí1 ) were optimized through inverse modeling and were used as solute transport and reaction input parameters of the model which predicted daily change in NO3-N of profile with reasonable accuracy (R2 = 0.83; RMSE= 4.62). Since NH4-N disappeared fast, hence it could not be measured frequently and therefore not enough data set could be generated for their use in calibration and validation of model.ThesisItem Open Access “Studies on Thermal Properties of Soils and Modeling of Heat Conduction under Different Soil Management Practices(DIVISION OF AGRICULTURAL PHYSICS, 2009) Pragati Maity; Pramila AggarwalHeat transport in soil is mainly dependent on soil thermal properties which are governed by inherent properties of soils such as their mineralogical composition, texture, colour etc and are also influenced by management practices like incorporation of manure, planting methods and mulch application . In order to study the influence of mineralogical composition and texture, a laboratory study in PVC columns was also carried out to compare the thermal properties of three different soil types (red loamy sand, black clay and alluvial sandy loam) maintained at two bulk density levels. In order to study the influence of management practices a field experiment was conducted during kharif season of 2008 at IARI, New Delhi on bare soil in split-split plot design with three manure types as main treatments (green manure, compost + charcoal and no manure), two land configuration (bed and flat system) as sub treatment and two mulch types (transparent polythene (175 µm thickness– TP and no polythene-NP) as sub-sub treatment. Results of laboratory study revealed that throughout the study period, in all soil types the difference in peak soil temperature (ST) between 0 and 20 cm soil layer reduced by 50% or more with increase in compaction level. Monitoring of ST at hourly interval on different days after saturating the columns showed highest magnitudes of ST at all depths all throughout the day in black soil followed by red and lowest in alluvial soils. However, the thermal properties were highest for black soil followed by alluvial soil and were lowest in red soil. Results of field study revealed that irrespective of manure type and mulch application, conventional planting system had significantly lower ST (1-2 °C) and higher soil water content (SWC) (1.5 to 2%w/w) than bed planting system. It was also observed that incorporation of compost + charcoal in plough layer of conventionally tilled soil alone increased the temperature by1.5-2.5 °C over no manure incorporation. Application of TP as mulch increased maximum surface ST by 4.5-6.5 °C over NP. In general, average ST of 0-20 cm under Compost +charcoal and no manure treatments were significantly higher and SWC were lower (0.9 % and 1.6 %) than under green manure treatment. Monitoring of ST at hourly interval during day time showed that peak ST at surface had 5-10 ° C higher magnitude and arrived earlier than peak ST at 15-20 cm soil depth. It also revealed that surface ST of bed covered with TP in compost +charcoal treatment had highest magnitude and of conventional system covered with NP in green manure treatment had lowest magnitude all throughout the day. All thermal properties were higher under conventional than in bed, in green manure than in compost+ charcoal and no manure and in TP than in NP. Computed thermal properties were used in modeling heat transport by using numerical solution of second order heat transport equation and Hydrus 1D. In both models, simulated ST as function of depth and time were in agreement with observed ST. The above results thus leads to conclusion that incorporation charcoal in plough layer followed by making of beds and application of thick transparent polythene could raise the surface soil temperature of bare soil by 10 ° C which could be a useful technique for soil solarisation. The above studies also suggest that both Hydrus-1D model and finite difference technique can be used to simulate soil temperature with fair accuracy.