Increasing soil organic carbon (SOC) is vital in terms of improving the soil physical and mechanical properties related to conditions for tillage and traffic, and to crop development in arid and semiarid regions. This studywasconducted to characterize theSOC, bulk density (BD) and consistency limits (shrinkage limit, SL; plastic limit, PL; liquid limit, LL) of a calcareous soil (Typic Haplargids) in relation to the seven-year application ofmanures(municipal solid waste compost,MSWC;sewage sludge, SS; farmyardmanure, FYM) at three rates (25, 50 and 100 Mg ha1) and one inorganic fertilizer (NP) management in irrigated wheat– corn rotation. There was also a control treatment (UNF), i.e. without any organic and/or inorganic fertilizer addition. The SOC, BD, consistency limits, plasticity index (PI = LL PL) and friability index (FI = PL SL) were measured for the soil taken from the 0–20 cm layer. The SOC in SS, FYM and MSWC treated soils increased on average by 2.5, 2.2 and 2 times of theamount in the UNF, respectively. The BD varied from1.03 to 1.37Mg m3. ThelowestBDwasrecorded in100 Mg ha1 applicationrate ofmanures,whereas itwasthe highest inNPtreatment. The PLandLL varied from19%to30%and30.1%to 40.9%, respectively. The PL for the SS treated soil was significantly higher than the FYM andMSWC treated soils. However, the LL and PI were not significantly affected by manure type. The SL and PL were increased significantly but in small percentagesbytheapplicationofNPas comparedwith theUNF. Theoptimumwater content(WC) for tillage (i.e. 0.9PL) as well as theworkableWCrange (i.e. FI) was the largest in the soilamended with 100 Mg ha1 of SS and the smallest in the UNF. There was a significant relationship between the application rate of the manures and theSOC. The positive relationship betweenSOCand SL, PL, LL or FIwasfoundto be significantly linearwhereas the relationship with the soil BDwassignificantly negative. For soilsamendedwith SS which the data on cation exchange capacity (CEC) were available, the relationships of PL and LL with CEC were significantly linear aswith SOC. This study showed that the manures improved soilWC ranges at which the optimum conditions for tillage and traffic can be obtained. Moreover, the improvement depended on the application rate of the manures.
کلید واژگان :Bulk density Soil organic carbon Consistency limits Optimum water content for tillage Friability index Fertilizer
ارزش ریالی : 600000 ریال
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