Recent Research Work

New Zealand Journal of Agriculture, Volume 90, Issue 5, 16 May 1955, Page 513

Recent Research Work

I PHOSPHATE TOPDRESSING § , - ■- -A- - ■/ • ‘ ’i

kyiUCH interest has been taken recently in investigation into * ’ * the most efficient rate of phosphatic topdressing for grassland. Optimum rates will naturally vary with soil type and prior treatment and the following notes give the interim results from a trial at the Winchmore Irrigation Research Station designed to investigate what annual superphosphate dressings are necessary to maintain a high level of pasture production under irrigation.

TREATMENTS AND MANAGEMENT

THE trial area, on Lismore shallow silt loam, is divided into 20 small fields, each of which constitutes a plot and

consists of a single irrigation “check” of approximately | acre. There are five superphosphate treatments, each replicated four times. The annual rates of application of superphosphate per acre are: Nil (control) , l|cwt., 3cwt., and 4|cwt., all applied in autumn, and 3cwt., half of which is applied in autumn and half in spring. In addition each plot is divided longitudinally into 2 lime sub-plots, “no lime” and “lime to requirements”. The trial is irrigated as required, results of soil moisture determinations being used as a basis. Pasture production is measured by the frame technique. Grazing of the trial is aimed primarily at maintaining even and adequate control of growth. To avoid possible transference of fertility in the dung and urine each treatment is grazed by a separate flock, which grazes in rotation the four replications of the treatment only. Control of pasture growth is maintained by the addition or removal of sheep. The sheep are tagged, shorn, and weighed before introduction to the trial and weighed regularly thereafter. When the trial was laid down the 2-year-old pasture was perennial ryegrass clover dominant, with dogstail prominent in spring and cocksfoot and Montgomery red clover in autumn. Timothy, and short-rotation ryegrass, which had been included in the mixture, were seldom seen in the sward. The area had been ploughed out. of browntop pasture in June 1948 and had received 2 tons of lime and 3cwt. of superphosphate in the 3 years before the start of the trial. Soil tests taken before the first topdressing showed a pH of 6.2 and a phosphate level of 4 to 4.5 (low to medium on this soil type). In May 1952 the first of the annual superphosphate dressings was applied. In addition 3cwt. of limestone was applied to the lime subplots in both 1952 and 1953. Grazing began in September 1952 and continued until May 1953. In the next season stocking began in September and the last sheep were removed at the end of April 1954. Except during the flush each spring, control and utilisation of the growth have been good. Stock health on all treatments has been excellent, though some scouring occurs in spring. Most of

the sheep (2-tooth wethers) are fat when removed from the trial.

INTERIM PRODUCTION DATA

Production data for the first two seasons are given in the table. In dry matter production all superphosphate treatments gave large increases over no superphosphate. This response was slightly greater in the

second year.

(No superphosphate = 100)

Agreement between pasture production and livestock figures is quite good, but sheep numbers are probably too small for much importance to be attached to the stock figures. When the results are being considered it must be remembered that the pH and phosphate levels of the area: when the trial began were higher than those found on. undeveloped land.

—S. D. WALKER

MINOR ELEMENTS

BY the middle of this year about 200 new observational trials will be under way to secure information on pasture requirements of sulphur, magnesium, boron, copper,, zinc, vanadium, and.

manganese applied singly and in combination. The following pasture responses to minor elements have already been obtained in current experiments. — Sulphur responses were secured as early as 1928 on lucerne in Central Otago. Pasture responses tosulphur, however, were observed first about 3 years ago. on the “tarry” soils (Waiareka complex) of North Otago. Since then marked responses to sulphur and various sulphates have been obtained on several soils in Canterbury and. on Tarawera gravel in Bay of Plenty. Boron Despite the general occurrence of the deficiency disease brown heart in swedes and turnips pasture topdressing trials so far have failed to demonstrate clear boron responses on pasture. Magnesium— Magnesium has been tried extensively in various forms. A serpentine rock finely ground was used in some 30 trials without conclusive results at the beginning of the Second World War. In more recent trials a response to magnesium carbonate was recorded on Ketu silt loam in the Marlborough Sounds and on Pinaki sand north of Auckland. Copper— Cunningham observed a growth response of pasture on a peat soil at Waitakaruru, where he successfully demonstrated copper deficiency in cattle and sheep.. During the last 2 years experiments on pastures have: indicated that several important soils derived from windblown sand and pipe clay gumland soils north of Auckland', as well as peat soils may require copper for maximum pasture production. Zinc — responses on pasture have been observed in. two instances on relatively raw coastal sand and a fleeting: response to zinc was recorded on a peaty pumice soil near Te Aroha. Sodium The application of sodium chloride (salt) may be of value on some potash deficient soils, particularly in the Bay of Plenty. Responses have been recorded to vanadium in theKaitaia district, Northland, to tungsten at Outram, south of Dunedin, and to nickel in a pasture mowing trial nearGore.

—C. DURING

Superphosphate Pasture production (dry matter)> per acre ’ Liveweight gains per acre Grazing days per acre 1952-53 1953-54 1952-53 1953-54 1952-53 1953-54 Nil 100 100 100 100 100100 IJcwt. 145 158 130 132 137 153 3cwt. .. 156 169 137 135 136 179 4Jcwt. 157 172 127* 146 135* 194 IJcwt. in spring IS cwt. in autumn [• 155 181 136 157 137 166

RELATIVE PASTURE AND LIVESTOCK PRODUCTION (No Superphosphate = 100)