TOP-DRESSING

Manawatu Standard, Volume LVII, Issue 159, 7 June 1937, Page 12

TOP-DRESSING

RESULTS IF EXPERIMENTS. DEPARTMENTAL REVIEW. Indicating the line along which topdressing trials are being developed by the Department of Agriculture, and bringing to notice some of the more important general results of the work, so far as it has gone, Mr C. J. Hamblyn, Superintendent of the Fields Division of the department in this district, addressed those attending the annual sheep farmers’ gathering at Massey College, last week. Mr Hamblyn emphasised that it was not intended to give any specific advice on the use of fertilisers in top-dressing. “During the past eight to ten years 300 observational trials have been laid down and recorded regularly on varying types of pasture and under varying conditions of soil and climate throughout the area under review,” Mr Hamblyn said. “These trials are small and inexpensive and have been designed as part of a scheme for a fairly rapid survey of fertiliser responses. In the early trials lime, potash, phosphate and nitrogen alone and in combination were used, but in later trials the nitrogenous manure was eliminated. Standard quantities of fertiliser of each type were used, the purpose of the trials being to find out whether the particular locality or soil type gave a response to lime, to potash or to phosphate, or to combinations of these and, if so, to record, as far as possible from observations, the degree of response. “It should be noted that a potash deficiency cannot be made up by an increase in the phosphate supply and, vice versa, nor can a definite lime deficiency be made up either by extra phosphate or potash except in so far as a minor shortage of lime occurs which prevents the full response to super may be remedied by using a basic phosphate like .slag or North African phosphate. It is therefore safe to say that a marked or definite phosphate response is best remedied by the use of a phosphatic manure; a definite lime response is best met by the application on lime ; and a definite potash response by the application of potash. “Very few of the trials under review have failed to give fairly definite evidence of deficiencies in one or other of the three major fertilising or soil improvement materials. It is fully realised that much country remains to be covered by this somewhat simple type of experiment, hut the results so far obtained, particularly when correlated with soil and pasture types and farm practice, indicate their value in adding to our present knowledge of fertilisers.

PHOSPHATE. “In all trials superphosphate has been used at 3cwt per abre and in a largo proportion in districts of high rainfall slag has also been tried,” Mr Hamblyn added. “Generally, all districts have shown a definite response to phosphates, the response being marked in some cases by natural high fertility and in others by previous regular top-dressing. Farming experience in most of these cases has demonstrated increased production from phosphate manuring, and it is evident that heavier applications are necessary to give visible response, particularly where white clover is strong in a good sward intereseting to note. that ,3cwt of phosphate in areas of high rainfall do not give the marked response and change in sward that the same quantity does on similar swards in districts of lower rainfall. This i,s particularly noticeable in comparing responses m Central Hawke’s Bay. Southern Poverty Bay and the Wairarapa with the results in Taranaki, Wanganui and the Manawatu. In the drier districts 11 cwt of phosphate will give a response similar to 3 to sewt in the wetter districts. “In comparing slag with superphosphate the point is that, whereas superphosphate is definitely satisfactory in areas of low rainfall, slag gives a similar response to superphosphate in areas of higher rainfall and tends to K) better in the initial stages of improvement where there is a tendency to a lime response. It is possible that the swing from slag to superphosphate then back to slag, prevalent in North Taranaki, is really due to the. fact that neither is giving really satisfac■fcorv results because of the fact that potash is also required to get really good responses.

POTASH. “Thirty per cent, of potash was applied at the rate of 2cwt per aoie per annum in all trials, and it can be definitely said that there is no difficulty in seeing a response to potash, though, strangely enough, chemical analysis of the soil is apparently a very uncertain guide. Further, potash responses cannot as yet he definitely related to soil types. In North Taranaki 26 out of 29 trials gave a definite response to potash and in some 16 of these • trials there was a still better response to phosphate and potash than for either treatment alone. It is interesting to note that in this area lime alone gave little or no response and lime phis sulphate only [slight improvement in most cases over phosphate alone. With the exception I ~f some early responses to potash round Ilaetihi, no other general potash re-

sponses in the districts other than Taranaki have been recorded. LIME. “In the Wanganui district tiie majority of the trials have shown a fairly definite response to lime alone, and in practically all cases from the coast to Ohakune and from Maxwell south to the Rangitikei River, lime and phosphate have given a definitely bettor response than either alone. “In the Manawatu, where the experiments extend from Apiti and Kimbolton south to Otaki, and include the Woodville county, the main response has definitely been from phosphates. Lime alone has given very slight, if any, response, and lime and phosphate in few cases only an improvement over phosphate alone. The Wairarapa experiments have shown generally some improvement for lime and potash oyer phosphate alone, but no outstanding results from lime- alone. Throughout Hawke’s Bay the main response lias been to phosphate with lime, giving a response in conjunction with phosphate in some of the southern districts, but seldom alone. “The trials with nitrogen in the original observational experiments confirmed the evidence of field trials, that the response was fleeting and largely connected with the type of sward paiticularlv with the proportion of rye. The claims that artificial nitrogenous manures markedly improved the sward perm tine ntly were not substantiated, but slumping of growth in November and December was often recorded.

THE CONCLUSIONS. “The survey has so far shown that there is a definite potash deficiency in parts of Taranaki, particularly in the northern districts, and that potash is well worthy of a trial by farmers there and also round Raetiln,” Mr Hamblyn concluded. “It has also been shown that there is no very definite lime shortage in the area covered as yet by the trials, but that in certain localities, such as Southern Taranaki, Wanganui, Marton, Hunterville, parts of the Wairarapa and Southern Hawke s Bay lime added to phosphate is likely to give better results than phosphate alone. Further, the survey emphasises the paramount importance of phosphates, particularly of superphosphate in North Taranaki, Manawatu, Central and Northern Hawke’s Bay and in Poverty Bay, and to, a lesser degree in all other districts.