Pasture

A pasture is a standing crop of perennial grasses and legumes kept for animals to eat where it grows. The plants turn sunlight and rain into feed, and the animals harvest it themselves, dropping their dung back where they took it. Cutting the same plants for hay carries those nutrients off the field, which is why hay ground is soil-tested yearly and grazed ground every second year.

What keeps a pasture alive is the leaf left behind. A grass plant stores the energy for its next growth in its roots and the bottom few centimetres of leaf, so the rule is to take about half and leave the rest: roughly 7 to 10 cm (3 to 4 in) of residue on cool-season grasses. Graze closer and the stand thins, the legumes going first because animals pick them out. Cool-season plants such as orchardgrass, timothy and clover slow above about 27 degrees C (80 F); warm-season ones need soil near 18 degrees C (65 F) to germinate and grow on past 32 degrees C (90 F).

That leaves a gap in the hottest weeks, which is where most pastures fail. A stand of one grass species offers only bad choices: too few animals and the spring surplus has to be cut, too many and bought feed covers the lean months at about twice the cost of grazed forage. Closing it takes a planned sequence: cool-season perennials, warm-season species for the heat, and growth rested in late summer and left standing for winter grazing, called stockpiling. Stock numbers follow the leanest month, not the average one. It works alongside the rotation that schedules grazing, water carried to each paddock, fencing, and winter shelter. Clovers fix nitrogen from the air, some 85 to 225 kg per hectare a year (75 to 200 lb per acre), so overseeding and liming to hold them in the mix is the main recurring cost. A stand let go too far cannot be fixed by scattering seed into it; an annual crop for a season or two clears the old sod.