Recent Research Work

New Zealand Journal of Agriculture, Volume 89, Issue 5, 15 November 1954, Page 505

Recent Research Work

PHOSPHATE TRIALS AT INVERMAY

POURING the past 4 years a number of trials have been laid down on the undulating second-class hill soils at the Department .of Agriculture's Invermay Research Station, Otago, to investigate various forms and rates of application of phosphate. The soil type is defined as a silt loam overlying clay and belongs to the yellow-grey earth group. It is deficient in phosphate, lime, and molybdenum. This soil type is very responsive to topdressing and in a highly improved state it will carry 4 or more ewes and their lambs per acre.

COMPARISON OF PHOSPHATIC FERTILISERS

THREE years’ results are available from a trial which compared superphosphate, ground North African rock phosphate, and ground Nauru rock phosphate, each

applied annually at 3cwt. per acre, and a treatment with an initial dressing of lOcwt. per acre of Nauru phosphate followed by annual dressings at 3cwt. Thermophos”, which is a fused calcium magnesium phosphate produced in the United States of America, and serpentine superphosphate were each included at rates to give a total phosphoric acid dressing equal to that in 3cwt. of superphosphate. Ground limestone at rates of nil, lOcwt., and 1 ton per acre each year were included as main plot treatments. Basic dressings were muriate of potash (lewt. per acre annually) and an initial dressing of 2|oz. per acre of sodium molybdate.

Superphosphate and “Thermophos” have given pasture yields significantly greater than the rock phosphate treatments and serpentine superphosphate. Nauru phosphate at 3cwt. per acre is the lowest yielding of the phosphate treatments, yielding significantly less than North African phosphate. The rock phosphates treatments have performed relatively better on unlimed ground. The response to superphosphate has been marked, production being more than double the control “no phosphate” in 1952-53. Despite this response, the soil phosphate level, as measured by the quick test method, has not been substantially improved on the superphosphate plots. Some sward changes are now becoming evident. In the control plots flatweeds and weed grasses (browntop, sweet vernal, and Yorkshire fog) have increased in percentage, and in the . best treatments short-rotation ryegrass is prominent. DRY MATTER YIELDS OF PASTURE HERBAGE FOR 1952-53 SEASON .. .. SerpenNorth tine Super- African Nauru Nauru superphos- phos- phos- phos- “Thermo- phosControl phate phate phate phate phos” phate 3cwt. 3cwt. 3cwt. lOcwt. lb. lb. lb. lb. lb lb lb No lime .. 5,900 ’ 9,450 8,450 7,350 8,300 9,450 8,700 lOcwt. lime 5,900 10,250 7,250 7,100 7,750 9 550 9 000 1 ton lime 5,850 9,900 7,050 6,250 7,500 600 <l’4oo

RATES AND TIMES OF APPLICATION OF PHOSPHATES

The trial of rates and times of application of phosphates was laid down on 9 March 1951 and included three forms of phosphate (superphosphate, lime-

reverted superphosphate, and North African phosphate) at rates of application per acre from IJcwt. to 6cwt., some applications being twice yearly and some annually. Autumn applications were made in February or March and the spring applications in September or October. As the calcium status of the soil has remained high, no lime has been applied since 1950, but a basal dressing of 2|oz. of sodium molybdate -was applied to all plots in 1952.

Superphosphate has been the highest yielding treatment in this trial, especially during winter and early spring, but the trial design does not compare forms of phosphate with precision and this superiority of superphosphate has not attained statistical significance.

The other comparisons are made more accurately and these have shown a consistent, and significant superiority of the.6cwt. per acre per annum phosphate dressing over 3cwt., the difference amounting to 14 per cent, in 1952-53 High yields have been obtained from the 6cwt. of superphosphate treatments. In 1952-53 these treatments produced over 12,0001 b. of dry matter per acre or sufficient to feed about 8 ewes and their lambs per acre. As this yield would be comparable with that from an average Waikato pasture, it indicates the value of heavy initial phosphate dressings and regular maintenance applications on permanent hill pasture on this soil type. This sward ls 6 years old. As a result of the high fertility, shortrotation ryegrass is still prominent in this sward and is producing well in winter and early spring.

Yields were not improved by splitting the phosphate dressings into autumn and spring applications rather than applying it all m autumn.

Responses to superphosphate dressings were rapid the maximum effect being evident about 6 weeks after application Reverted superphosphate and North African phosphate usually took 3 months or longer to give the most benefit. With the provision of adequate phosphates, lime potash, and trace elements, second-class hill land similar to that at Invermay should improve rather than deteriorate and retain a high stock carrying capacity for many years

ALTERNATIVE FERTILISERS TO SUPERPHOSPHATE

This trial was laid down on 8 August 1951 to investigate alternative fertilisers to superphosphate. The sulphur supply position is not secure and it is desir-

~ x . able to investigate phosphatic fertilisers that do not require sulphur in their manufacture. Several new products and basic slag and granulated superphosphate were included in this trial. The phosphate treatments applied per, acre each year were superphosphate umu ■’ and „ basic slag, granulated superphosphate, Thermpphos”, “Fused Tricalcium Phosphate”, “Calcium Magnesium Phosphate”, oxalic superphosphate, and Calcium Metaphosphate” were applied at rates to give an equivalent phosphoric acid application to that of 3cwt of superphosphate. A control plot was also included. A basal dressing of 2|oz. of sodium molybdate was applied to all plots in the trial. “Thermophos”, “Fused Tricalcium Phosphate , Calcium Metaphosphate”, and “Calcium Magnesium Phosphate” are all “fusion” products made by fusing phosphate rock with different materials, usually magnesium-containing minerals. Oxalic superphosphate is an experimental mixture in the manufacture of which oxalic acid is used in place of sulphuric acid to react on phosphate rock m superphosphate manufacture. tSk Al V h ??, e P hos P h fertilisers except “Fused Tricalcium 1 hosphate gave herbage yields similar to those of superphosphate. “Fused Tricalcium Phosphate” has yielded slightly but significantly less than superphosphate. In another trial where molybdenum was not applied basic slag gave yields markedly superior to those of superphosphate. This suggests that the small molybdenum content of basic slag may have a beneficial effect in some circumstances. —N. A. CULLEN