Newly Developed Scrub Land Needs Heavy Topdressing

New Zealand Journal of Agriculture, Volume 101, Issue 1, 15 July 1960, Page 17

Newly Developed Scrub Land Needs Heavy Topdressing

By

G. J. BATTEN,

Farm Advisory Officer, Department of Agriculture, Thames

MANY virgin soils being developed from scrub and fern in the Auckland Province lack especially nitrogen and available phosphate. Pastures will not grow satisfactorily on soils deficient in these elements. NITROGEN build up will be rapid under stocking on a vigorous clover pasture. Nitrogen return from dung and urine and trampled in plant residues may be equivalent to about lg tons of sulphate of ammonia in a year. However, pasture will not establish and grow vigorously unless the phosphate and any other soil deficiencies are corrected. Soil test figures for available phosphate on some of these soils are very low and 9 cwt of superphosphate is needed in the first year. Originally this was applied in three dressings of 3 cwt: at sowing; after four to five months; and again the next autumn. The pasture grew well if the second application was on time, but too often it was delayed to six to seven months after sowing and the clover received a severe check. A. V. Allo, Tauranga, reported in the March 1957 “Journal” that where growth continues for most of the year a heavier rate of phosphate initially is desirable rather than spread over several dressings, and that with a heavier rate of phosphate the seeding rate could be reduced. Farmers have been quick to adopt a lower seeding rate, but some have been loath to increase topdressing rates correspondingly, leading to unthrifty, weedy pastures, some of which need resowing. If 9 cwt of superphosphate is needed in the first year, 6 cwt should be sown with the seed and the balance in the following spring to autumn. The high costs of land development have encouraged the cheaper method of crushing and burning the existing vegetation, oversowing, topdressing, fencing, and stocking. This method also has the advantage of not disturbing the consolidation that is so vital in seedbeds on light soils. However, it does result in a lot of regrowth weeds such as fern, manuka, and tauhinu, which need judicious mob stocking to control. A good pasture is necessary to compete with these weeds and to withstand heavy stocking. Provided cultivation and sowing are correct, heavy initial topdressing will ensure good pasture establishment on these soils.