Tillage involves mechanically manipulating soil to prepare it for crop production. The main objectives of tillage are to obtain a deep seed bed, add fertility and humus, destroy weeds, aerate the soil, increase water absorption, destroy pests and reduce erosion. Primary tillage such as ploughing is the initial major soil working operation using implements like mouldboard ploughs and disc ploughs. Secondary tillage with implements like harrows then further conditions the soil for planting. Different tillage systems exist such as minimum tillage, strip tillage, and mulch tillage.