Production of Pasture Seed
The more important grass and clover seeds saved for pasture sowings are:
Over 60 per cent of the area harvested is in the Canterbury Land District, and 20 per cent in the Otago and Southland Land Districts. The North Island contributes under 15 per cent.
Areas most suited to grain harvesting are also preferred for the saving of grass and clover seed. The two activities are integrated in the arable-farming programme. The acreage closed for seed each year is governed both by seasonal conditions and by likely prices.
Ryegrass Seed: Similar practices apply to the saving of the three ryegrass species – perennial, short-rotation, and Italian. As these may all interpollinate, and as mechanical separation of the seeds is impossible it is important for seed production that only one species be sown in one area. Pastures for seed are established by the sowing of from 15 to 25 lb of ryegrass seed and 2 to 3 lb of white clover seed per acre. It is usual to sow rather more perennial seed than that of the other ryegrass species. Montgomery red clover or cowgrass seed may be used as an alternative to the white clover, particularly when Italian or short-rotation ryegrass seed is being sown. The grass benefits from the nitrogen-fixing habits of the clover and a higher producing and more palatable pasture results. It is usual to broadcast the seed on a moist, well consolidated seedbed after a fallow, but in dry districts it may be better to sow the seed through a 3½ in. centre-disc coulter drill. In the North Island sowings may be delayed until April or even May. In Hawke's Bay it is more usual not to sow any clover seed with ryegrass, as clover comes in strongly as a volunteer. In Canterbury February or March sowings are preferred; in Otago and Southland sowings are still earlier. It is usual, especially in the South Island, to apply a ton of lime to an acre just before sowing and a hundredweight of phosphatic fertiliser with the seed. The resulting pasture is stocked to control the growth and to allow white clover and ryegrass to become established. But unreasonably severe grazing may adversely affect the ryegrass. The final grazing before closing usually takes place in October, though strong-growing pastures on fertile soil are often not closed until November. After the final grazing the pasture may need topping with the mower to cut unevenly grazed patches and to even up the sward. At this stage nitrogenous fertiliser will stimulate the ryegrass and benefit the seed crop. Ryegrass is ready to harvest usually in early January, when the first seeds have begun to shake. The best method of harvesting, particularly in heavy crops, is to cut the crop with the reaper and binder and tie it into fairly small sheaves, which are then stooked for 10 to 14 days before threshing. The more common practice, however, is to windrow the crop either with the mower (or with a reaper with its binding mechanism removed) and to use the header to thresh the crop out of the windrow. Light crops may be directly headed, but the seed then needs to be spread out evenly for drying before it is bagged tightly. This is a more useful practice in second-year crops which have been managed primarily for white-clover seed, but contain some ryegrass seed which matures earlier.
White Clover Seed: Pastures saved for ryegrass seed in the first harvest season are often managed to produce white clover seed in the second, though other pastures which have become white clover dominant may also be used for that purpose. White clover is slower to establish than ryegrass but comes away after the ryegrass seed crop has been harvested. During the following winter and spring heavy grazing keeps the ryegrass in check and encourages the development of a clover-dominant sward. The best management entails even and reasonably close grazing alternating with spelling until the first flower heads begin to appear. The paddock is then closed for a seed crop, usually in late October, or later on naturally moist land or land which can be irrigated. At that stage, if the weather is dry, the plants are ready to expend their energy in producing seeds rather than leaves, though in a wet district or season the improved strains of white clover will continue to produce leaf growth which smothers the flower heads. White clover crops flower for a long period. Experience alone tells when a crop is at the best stage to harvest. The number of heads containing ripe seed is the main guide, but weather and the amount of clover-leaf growth can influence the decision. The crop is harvested by cutting it with a mower, leaving it to dry until the heads are brittle, and then threshing with a header harvester fitted with a pickup. If second growth develops before the crop can be threshed it may be necessary to undercut the windrow with the mower to facilitate drying.
Red Clover Seed: Cowgrass, an early or double-cut type of red clover, is grown mostly in Marlborough and Nelson. Montgomery red clover, a late or single-cut type, is more often grown in Canterbury and North Otago. If cowgrass and ryegrass are sown together the area is managed for a ryegrass-seed crop in the first harvest. More often the ryegrass is omitted and the cowgrass seed is sown either in autumn or spring immediately after the drilling of a cereal crop, or in spring with a rape crop. In either method 5–6 lb of cowgrass seed per acre are sown. Some growers sow up to 10 lb when ryegrass is not included. Phosphatic fertiliser and lime are applied as for ryegrass and white clover crops. After the ryegrass seed or the cereal crop has been harvested, or the rape crop fed off, the stand may be lightly and intermittently grazed until early spring, or it may be treated solely for hay and seed production without grazing. It is usual to take a hay crop in the second half of November or in early December. The second growth is saved for a seed crop the following autumn. Cowgrass seed ripens unevenly but the crop may be mown when the majority of the heads contain mature reddish-purple seeds and, depending on the weather, left in the swath for a fortnight before threshing. Most crops are ready for harvesting in March or early April. Seasonal management can be repeated to obtain a second crop in the subsequent season, but the areas are seldom retained longer for seed.
Although Montgomery red clover seed looks like cowgrass seed, the plants are slower to come away in the spring and do not usually put on enough growth for a hay crop before the area is closed for seed. Montgomery red clover seed is seldom sown without ryegrass (even in the spring under cover of a cereal, linseed, or rape crop) as it is difficult to control the following season's growth when pure sowings are made. Montgomery red clover is seeded rather more lightly than cowgrass, but other establishment practices are similar. Montgomery red clover stands may be saved longer than cowgrass for seed crops. They benefit from a phosphate topdressing before closing for seed each year. Older stands usually yield less seed.
It is sometimes practicable, on heavy land, to take a hay crop before saving for seed. More often the area is grazed with sheep until the end of October or November. Grazing is light and intermittent until vigorous growth begins, when heavy grazing is maintained until the area is closed for seed. In a dry season Montgomery red clover seed may be ready to harvest in late March or April, as there is little second growth of leaf to hinder operations. But in wet seasons harvesting may be delayed until frosts have cut back the leaf growth. Seed may be harvested in the same way as cowgrass seed, but it is more usual to wait until the leaf growth is dead and then to direct head the crop. More recently it has become common, when the seed is mature enough, to spray the crop with a leaf-defoliant or crop-desiccant chemical, which reduces leaf growth and hastens maturity. Direct heading can begin within a few days of treatment.
Cocksfoot Seed: Cocksfoot seed growing, once centred on Banks Peninsula, is now carried out in suitable districts in Mid and South Canterbury and in Southland on land where harvesting can be mechanised. Open-textured soils of reasonable fertility, in good heart and as free as possible from grassy weeds, are most suitable. It is usual to make a pure sowing of cocksfoot seed in December or January after a fallow. Stands so established produce a seed crop in the following season. The seed is drilled through every coulter, or broadcast, though English practice suggests that better yields are obtained if the stand is sown in 21-in. or 28-in. drills and the rows intercultivated. Phosphatic fertiliser is applied when the seed is sown. Where annual weed growth is a problem it may be better to sow the seed in spring under cover of a cereal crop. Seeding rates vary from 5 to 8 lb an acre or more when broadcast. Widely spaced rows are more lightly seeded. There seems no advantage from including white clover seed in the sowing.
Cocksfoot seed stands are harvested for many seasons, though yields tend to become lighter as the age increases. Annual applications of a nitrogen fertiliser increase the yield of seed. In the first season from 1 to 3 cwt an acre may be used, and twice that amount in later seasons, either in one application in the spring or in two applications in autumn and spring. Light grazing of a cocksfoot seed stand by cattle in the autumn may be beneficial, perhaps more through the trampling in of the dead residues after harvest than from any direct benefit from the grazing itself. Heavy or uncontrolled grazing harms seed production; some growers prefer not to graze at all.
Cocksfoot seed ripens unevenly and it is difficult to judge the best stage for harvesting. Most crops are cut when some seed can be knocked out of the riper heads when these are hit on the hand. Cutting is best done with a reaper and binder set high to avoid as much leafage as possible. The sheaves are then stocked for a fortnight before threshing. Mowing the crop and threshing it with a header harvester from the windrow gives indifferent results unless the farmer is favoured with good weather from cutting to threshing.
Timothy Seed: Timothy seed requires soil conditions similar to those for cocksfoot seed. Timothy establishes itself best on a firm seedbed which has been fallowed and well limed. The seed is sown at 3–5 lb an acre, either broadcast or (preferably) drilled. It is better not to sow any white clover with the timothy, as white clover seed is an impurity that is very difficult to separate. The seed is usually sown without a cover crop in December or January after a fallow; but in Southland, where considerable seed is produced, it is commonly sown earlier with rape as a cover crop. Timothy seed stands may be lightly grazed in the first autumn to help to establish the young plants, but they are best closed to stock during the first winter. The spring growth may be grazed by sheep from August to about the middle of October, when the area is closed for a seed crop and topdressed with 1 cwt of superphosphate and 5 cwt of lime an acre. Management for subsequent seed crops is similar, except that once the crop is established heavy stocking during winter aids seed production and the feeding out of the threshed straw on the area returns most of the nutrient taken up by the seed crop. Timothy seed is not ready for harvesting until about March, the crop being fit to cut when the seed head can be stripped from the stalk when it is pulled between the thumb and the forefinger. The trend in harvesting is to cut with the reaper and binder with the knotting mechanism removed, leaving a fairly high stubble. The cut crop forms a windrow on this stubble, where it is left to dry out for up to three weeks or more before it is picked up and threshed with a header harvester. Some growers still prefer to tie the cut crop into sheaves and stook or even stack it until the seed is ready for threshing with a mill. This method is undoubtedly the best if labour and machinery are available.
Seed Quality: Several factors determine quality in agricultural seeds. Purity is important and, especially, freedom from harmful weed seeds. Machine dressing of all seeds is standard practice and much progress has been made in the design of machines for this work. The separation of some impurities is almost impossible, but seed growers can materially assist by cutting or spraying serious weeds in the seed crop before harvesting.
Seed must be able to germinate, but little can be done to preserve this capacity other than by seeing that the seed is mature, does not heat when harvested, is stored under good conditions, and is used before it ages. Almost all lines of seed are tested for purity and germination at the Seed Testing Station of the Department of Agriculture, and a satisfactory certificate of analysis of a recent test is the buyer's assurance of quality.
Reselected or pedigree strains of all the main pasture and crop plants have been produced by the Grasslands and the Crop Research Divisions of the Department of Scientific and Industrial Research. Nucleus lots of each kind are supplied regularly to the Department of Agriculture, which multiplies them and distributes them to seed growers. Further increase is made on a commercial basis, the product being certified under the seed certification scheme operated by the Department of Agriculture.
Varietal or strain purity must be maintained to get the best out of new varieties and strains. Buying certified seed protects the buyer, but much can be done by seed growers to see that varieties or strains are not mixed. It is always wise for seed growers to sow certified seed of the highest class to see that different varieties or strains which interpollinate or cannot easily be separated at dressing are not sown together, and that drills and harvesting equipment are properly cleaned. Seed-cleaning operators also need to take care so that seed is not contaminated or mixed during seed dressing.
by Jack Hean Claridge, B.AGR., DIP.AGR., Chief Advisory Officer (Agronomy), Department of Agriculture, Wellington.
- Arable Farm Crops of New Zealand, Hadfield, J. W. (1952)
- Crop Production, New Zealand Department of Agriculture, Extension Division (1953).