Use Of Liquid Fertiliser

Press, Volume CVIII, Issue 31659, 20 April 1968, Page 10

Use Of Liquid Fertiliser

Experiments have been going on in Canterbury using a specially designed machine to introduce liquid nitrogen fertiliser into the soil below surface leveL Because of the availability of liquid nitrogen at the Hornby chemical works several farmers and contractors were planning to have storage tanks and equipment for distribution of the liquid, Mr D. J. G. Davies, field research officer for Kempthorne, Prosser and Company, said this week. Mr Davies said that urea was the main form of liquid nitrogen being produced commerically at the present time and as demand increased it was envisaged that even cheaper forms of nitrogen would become available. However urea was probably one of the most versatile forms of nitrogen, being available in both solid and liquid forms. As a liquid it could be applied above the ground to crops by boom spray rigs operating from either tractors or aircraft The stage of growth of a crop would determine whether a ground or aerial application should be used. Many farmers and horticulturalists had been successfully using liquified urea for some time, but a completely new approach for this country had been the examination of the potential for direct application of liquid fertilisers below the ground. For this purpose a specially designed experimental applicator rig had been built in Christchurch with some components being imported from Australia. The machine consisted of a 50-galion mild steel cylindrical tank mounted on a standard A frame, at the rear of which could be suspended a granular fertiliser distributor. A diaphragm pump driven from the ground wheel developed sufficient pressure —up to 751 b to the square inch—to push the fluid solution through the plastic connector tubes and thence to injector tynes for placement at any desired depth up to Sin in the soil. Experimental solutions containing nitrogen and nitrogenphosphorus mixtures had been tested last spring (in August) under pasture on two soil types—one light and stony and the other a medium clay loam. The trials compared the responses obtained between surface applied solid nitrogen and nitrogen-phosphorus mixtures with identical rates placed below the ground. Very strong responses were obtained to the high rate of both the nitrogen and nitro-gen-phosphorus compound in both liquid and solid forms, but responses were less marked at the lower rates used. “The results, in general, are in agreemnt with overseas findings 'in that both solid and liquid nutrients can be expected to produce a similar response pattern where all conditions are optimal, as they were at this site,” said Mr Davies. There was an appreciably earlier response to the surface treatments applied through a new granule applicator than from the subsurface treatments placed 3in deep in the soil. However, the effect of the soilinjected treatments lasted for a much longer period, which Mr Davies said, posed the interesting question of whether, in fact, a combination of surface and subsurface fertilisers might be the most efficient method of

obtaining maximum productivity. On another site, using the same liquid materials as above, a comparison had been made between the effects of cultivation and no cultivation. Arawa wheat had been direct seeded over both areas as an indicator plant. Liquid nitrogen and nitrogenphosphorus had been applied on the surface and subsurface at 4in deep. Similar responses were obtained on both cultivated and noncultivated plots, except that the response in existing vegetation on the noncultivated site was obtained within three to four weeks. After five to six weeks the root system of the wheat plants reached the plant nutrient zone with a quite spectacular vegetative response being shown to the sub-surface application of compound liquid fertiliser. “Liquids are the most economical form of plant food even though they are not necessarily the cheapest,”

says Mr Davies. “The actual cost of a liquid on a per unit basis may be higher than solids, but there are other factors which can be taken into account in assessing a farmer’s per acre cost:—• “(1) Labour saving—the fast, efficient transfer and application of the material. “(2) Free flowing, metered, uniform - patterned application. “(3) The use of 50 foot booms means less trips across the paddock. “(4) Liquids may be combined with pesticides, herbicides and minor nutrients. “(5) Chemical analyses for liquids are almost always correct. “(6) Liquids are quick acting, yet long lasting. “(7) They are safe because they are under little or no pressure.” Liquid fertilisers were also more economical to merchandise than dry fertilisers because less manpower was needed to get the job done, said Mr Davies.