SUMMARY
The efficient use of carbon is the principle goal of achieving the agricultural and environmental sustainability. Thus, study was aimed to compare the C-equivalence (Ceq) of inputs and outputs and the C index of sustainability (Is). Five cropping sequences were; fallow–wheat (FW, Triticum aestivum) (control), mungbean (Vigna radiata)–wheat (MW), sorghum (Sorghum bicolor)–wheat (SW) green manure–wheat (GW) and mungbean-chickpea (Cicera rietinum, MC). Tillage systems included moldboard 14 plough (MP), deep tillage (DT) and minimum tillage (MT). The primary data collected were crop yield and the above-ground biomass. Fuel utilization in MP was 15.2 kg Ceq ha-1 with two ploughing per year, C input was 30.4 kg Ceq ha-1. In DT it was 11.6 kg Ceq ha-1. Herbicide used based input was 27.3 kg Ceq ha-1. The Ceq of outputs differed among tillage treatments, and were: 135, 112 and 80.47 kg Ceq ha-1 for MP, DT and MT, respectively. On the average of two years, the highest grain Ceq was measured under MP and under SW in winter (1040 kg Ceq ha-1). The maximum Ceq biomass was estimated in winter with MC (2867 kg Ceq ha-1). However, the highest root Ceq under MT was calculated in winter with MW (9500 kg Ceq ha-1). Under MT, the maximum Iswas obtained with MC for both years in summer (77 and 130). In winter of the second year, the highest Is was estimated for FW (82). These results showed that the efficient use of fertilizers, herbicides and farm machinery in the field under MT, with legume based cropping system, could be the best option to enhance the carbon Is in dry lands.