Crop Rotations and Soil Tillage Interactions for Biomass Production

Özet

The introduction of energy crops for biofuel production is expected to cause severe soildegradation as all crop material will be removed from the fields leaving the soil bare andsusceptible to soil erosion. The adoption of crop rotations to keep the soil covered by vegetation allyear round along with the application of reduced tillage or no-tillage methods can offerconsiderable soil protection. Basic criterion for an energy crop is the positive energy balance.Energy budgets for two energy crop rotations (in the first one all the plant material is removedfrom the field while in the second one the residues are left on the soil) and five tillage methodswere estimated. Crop rotations were combined with: 1. Conventional Tillage (CT), 2. Reducedtillage with heavy cultivator (HC), 3. Reduced tillage with rotary cultivator (RC), 4. Strip tillage ordisk harrow (ST/DH) and no-tillage (NT). The energy budget proved to be positive when the wholeplant material of a crop was used as an energy feedstock but turned to negative if part of it wasleft on the field and crop yield was not high enough. The first rotation presented higher net energygain as the whole plant material was utilized. Energy efficiency was higher in the ST/DH for bothrotations and all the crops. Soybean proved to be most efficient as a second crop in the year thansunflower. In sweet sorghum net energy was high due to the high biomass production but energyefficiency was low due to high energy requirements of irrigation. The most efficient crops were thelow-input, non-irrigated winter mixtures of vetch / oats and triticale / peas.