Irrigation brings its own feed management challenges

Press, 25 February 1983, Page 22

Irrigation brings its own feed management challenges

The higher stocking rates possible under irrigation create extra demand on the late winter-early spring feed supplies, according to a farm adviser with the Ministry of Agriculture and Fisheries in Rangiora. Mr Phillip Everest. Mr Everest has pointed out that the irrigation of the Amuri Plains, in North Can- i terbury, has greatly improved the ability of farmers i to produce heavyweight ' lambs on the good summer pasture. i But although irrigation had , greatly increased summer 1 pasture production, late winter and early spring growth ; was similar to that produced ; under dry land conditions. i

To provide the large quantities of grass necessary for lactating ewes, good autumn management was required. Mr Everest said good management steps which should be taken in autumn include: • Lambs for slaughter sold by early March. • Ewes need to be flushed three weeks prior to mating. • Autumn-saved pasture needs to be accumulated for i winter. •If feed reserves are low. ■ topdress ryegrass-dominant < pastures w'ith nitrogen in ' March. 1 Once feed had been i accumulated over he ' autumn, it was also import- i ant that it was managed

correctly during winter, he said. Winter rofation of 90 to 100 days should begin 30 to 40 days after the rams were joined with the ewes. Hoggets should graze their own area from mid May on two 50-day rotations, said Mr Everest. Supplements might need to be fed in the early stages of the rotation to maintain rotation length. Mr Everest said if feed supply was to be built up over the autumn then stock demand must be reduced and the, sale of all lambs for slaughter by early March would effectively achieve a reduction in stock demand. A successful lamb drop

next spring was only attainable if the ewes were in good condition and fed well at tupping. It was vital that ewes were at least maintaining weight, preferably gaining for the three weeks prior to the ram going out and for at least the first cycle. A rotation length of 30 to 40 days would be adequate over tupping and for ewes to be gaining weight they must be moved on while there was still feed remaining. Ewe lambs must be fed well until mid May so that a liveweight of at. least 35kg was reached prior to winter. If high per-head performance from irrigation was anticipated this must start with the improved rearing of

young stock so the ewe lambs should be grazed on a separate area to the ewes on a 30 to 40 day rotation, he said.

If feed reserves were low. it was possible to boost feed by the application of nitrogen to ryegrass-dominant pastures in March, and Mr Everest suggested the use of compound fertilisers containing both nitrogen and phosphate (e.g. D.A.P.. Ammophos. etc.) may be worth consideration if maintenance phosphate dressings have yet to be applied.

He said a 90 to 100 dav winter rotation started 30 to 40 days after joining would ensure that feed was available in the spring for lactating ewes when green grass is essential. Farmers should aim to shift the mob every two days, which may involve the use of temporary subdivision.

Supplements were normally only required early in the winter rotation when there was not enough grass to maintain ewe liveweight. Later in the rotation there would be enough grass present in the breaks and supplements would not be necessary. To ensure that hoggets were adequately fed over the winter they should be allocated their own area for grazing from mid May until August. The area to be laid aside for hoggets could be calculated by finding out the percentage of stock units as hoggets (0.8 of a stock unit) and reserving the same proportion of land.