Nutrient budgets and status in three pairs of conventional and alternative mixed cropping farms in Canterbury, New Zealand

agricultura alternativa agriculture alternative alternative farming azote azufre crops cultivo mixto cultivos fertilidad del suelo fertilisation fertilizer application fixation de l'azote fosforo gramineas graminee grasses mixed cropping new zealand nitrogen nitrogen fixation nueva zelandia pastizales pastures phosphore phosphorus plante de culture rotation culturale rotational cropping soil fertility soufre sulphur trifolium repens