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Properly managed manures have a high fertilizer equivalency and are thus a valuable source of nutrients in forage production systems. An efficient utilization of these nutrients, however, is limited by the crop's demand for nitrogen (N) and phosphorus (P). Moreover, environmental goals implied by the EU Nitrates Directive impose constraints on the use of manure and mineral fertilizer. Through calculations based on experimental data from various sources, the present study explores the limits on the use of cattle slurry and mineral fertilizer in grass and silage maize production on sandy soils in the Netherlands. The study concludes that cut grasslands can utilize cattle slurry up to average rates of 330–340kgN/ha (120kgP₂O₅) per year without exceeding a target value of 11.3mgnitrate-N/l in the upper groundwater or accumulating P in the soil, provided that (i) appropriate amounts of mineral fertilizer N are …