The constraints on conservation tillage in New Zealand are more philosophical than technical. The New Zealand pattern of using a pasture-crop rotation on arable land means that the renewal or restoration of pasture without cultivation is an integral part of the total low energy input system. Many of the pastures based on permanent species deteriorate over time because of damage from drought, climatic extremes, overgrazing, and pests in conjunction with imperfect management and fertility, all leading to an ingress of weeds and a lowering of productivity. Cropping fertilizers can be applied by surface broadcasting, mixing with the seed at drilling, or separated placement alongside the seed at drilling. The main purpose of tillage has been described as providing seedbeds with adequate soil moisture, aeration, consolidation, and freedom from weeds to encourage consistently optimum responses from seeds and seedlings during germination and emergence.