Effects of tillage systems on energy and carbon balance in north-eastern Italy

An energy analysis of three cropping systems with different intensities of soil tillage (conventional tillage, CT; ridge tillage, RT; no tillage, NT) was done in a loamy-silt soil (fulvi-calcaric Cambisol) at Legnaro, NE Italy (45 degrees 21'N, 11 degrees 58'E, 8 m above sea-level (a.s.l.), average rainfall 822 mm, average temperature 11.7 degrees C). This and measurements of the evolution of the organic matter content in the soil also allowed the consequences to be evaluated in terms of CO2 emissions. The weighted average energy input per hectare was directly proportional to tillage intensity (CT > RT > NT). Compared with CT, total energy savings per hectare were 10% with RT and 32% with NT, Average energy costs per unit production were fairly similar (between 4.5 and 5 MJ kg(-1)), with differences of 11%. The energy outputs per unit area were highest in CT for all crops, and lowest in NT. The RT outputs were on average more similar to CT (-12%). The output/input ratio tended to increase when soil tillage operations were reduced, and was 4.09, 4.18 and 4.57 for CT, RT and NT, respectively. As a consequence of fewer mechanical operations and a greater working capacity of the machines, there was lower fuel consumption and a consistently higher organic matter content in the soil with the conservation tillage methods. These two effects result in less CO2 emission into the atmosphere (at 0 degrees C and pressure of 101.3-103 kPa) with respect to CT, of 1190 m(3) ha(-1) year(-1) in RT and 1553 m(3) ha(-1) year(-1) in NT. However, the effect owing to carbon sequestration as organic matter will decline to zero over a period of years.