Seasonal Notes

New Zealand Journal of Agriculture, Volume 101, Issue 1, 15 July 1960, Page 47

Seasonal Notes

By Farm Advisory Division

NITROGEN FOR GRASS SEED CROPS

DECAUSE of the high cost of ■*-' nitrogenous fertilisers in New Zealand, their use on grassland can be justified economically only for purposes such as out-of-season grass production, winter grass production on town milk supply farms, and k grass seed production. Paddocks for grass seed production are usually closed from late September to mid October. The paddocks are first grazed well down, preferably with sheep, and are then harrowed and left.

Correct timing of the application is important to get the best out of a nitrogenous fertiliser. It is as well not to topdress the paddock when it is first closed. Leave the paddock for about two weeks; the soil will be warmer and the grass plants will have put forth some growth and will be better able to utilise the applied nitrogen. The grass plants will then tiller well, put up more seed heads, generally grow more vigorously, and thus produce a higher yield of seed. The best types of nitrogen to use are sulphate of ammonia and one of the commercial ammonium nitratelime mixtures. They are cheapest per unit of nitrogen. Organic nitrogen such as blood and bone acts too slowly for grass seed production and costs more per unit of nitrogen. From 1 to 2 cwt per acre of sulphate of ammonia or its equivalent may be applied. This rate will produce extra seed, which will more than pay for the outlay on nitrogenous fertiliser. Apart from increasing seed yield per acre, use of nitrogen improves seed quality and seed dresses out better. —C. J. CHRISTIE, Palmerston North

* * * BURY CROP RESIDUES TO REDUCE DRY ROT IN an effort to control dry rot the residues of all brassica crops should be buried by ploughing under; discing and other surface cultivation should be avoided. Dry rot may cause serious losses in swedes and turnips; it also affects rape, kale, chou moellier, and other brassicas, which are also carriers of the fungus. The disease attacks the leaves, stems, or bulbs of these crops, causing varying degrees of rotting in root crops and a somewhat less destructive condition known as “blackleg” in the leafy crops. The fungus carries over from one season to the next on crop residues and for this reason heavy dry rot losses are likely in the second of successive crops of swedes and turnips or in crops which follow other brassicas in the rotation. Kale, chou moellier, or rape crops sown after swedes are often almost entirely affected with the blackleg form, which may have little effect on the crop and pass unnoticed. There is, however, a rapid build-up in the disease, and residues of these second crops are a particularly prolific source of dry rot spores in the following year. Recently it has been discovered that the spores released from these residues' can be carried for considerable distances by wind and failure to bury all such residues may result in dry rot damage to swede and turnip crops over a wide area. Similarly residues left on the surface

after the sowing of pasture with a cover crop of rape, kale, or turnips could result in dry rot infection of root crops sown nearby. To reduce the losses caused by dry rot residues of brassica crops should not be left on the surface to liberate windborne spores. —S. M. J. STOCKDILL, Palmerston

* * * CARE OF SEED POTATOES AT this time of year seed potatoes are being graded and efforts should be made to ensure that a satisfactory sample is made by removing all diseased, misshapen, damaged, and moth-infected tubers as well as grading to standard sizes which have been adopted to allow for ease of mechanical planting. Avoid causing more damage to the seed at this stage, as this will be showing up badly by planting time. In districts where frosts occur the graded seed must be stored in shelter. Ideal places can be found under the sunny side of trees. Provided seed potatoes are well covered, they will keep better outdoors than in poorly ventilated and dark sheds or stores, where there is often too much warmth. Storage rots are frequently the result of poor storage conditions. Tubers affected in this way are usually soft and when cut show a dark or grey ring just beneath the surface. Once the risk of severe frost is over the bags can be laid out along the sheltered side of fences. Occasional turning will prevent excessive sprouting. This is important with some of the newer varieties. Removal of long sprouts often leaves the seed weakened and poor emergence will result. Dipping in fungicides just before planting to control corticium is becoming more common in many districts. Seed which has been sprouted in good conditions of light has small, firm, green shoots and will give earlier crops than unsprouted seed. —N. H. GREAVES, Timaru * * *

WEED CONTROL IN PASTURES

THE prevalence of certain weeds in a pasture may be the sign of a particular need. Improved drainage and less winter pugging will do much to reduce pennyroyal and buttercups; where flatweeds, dandelions, and ribgrass abound a shortage of potash is often likely, and until potash is applied use of

hormone weedkillers will do little to increase pasture growth. Where thistles are increasing, which is a sign of high fertility, use of hormone weedkillers is most effective. However, some of the high fertility weeds, including docks and Californian thistle, are harder to control. Pastures should generally be sprayed in early spring, when the weeds are small and leafy and before clovers start growing. MCPB and 2,4-DB are the hormones to use on weeds in new grass, because they do not harm young clover plants.

—G. B. HADDOW,

Auckland