Responses to Pasture Topdressing in Tauranga County

New Zealand Journal of Agriculture, Volume 82, Issue 6, 15 June 1951, Page 515

Responses to Pasture Topdressing in Tauranga County

By

A. V. ALLO,

Instructor in Agriculture,

Department of Agriculture, Tauranga

Z"\NE of the most striking features of New Zealand farming over the past decade has been the increasing interest shown by farmers in their pastures, particularly in pasture topdressing. For many years the Department of Agriculture has been conducting pasture topdressing trials throughout New Zealand and as a result it is now in a position to advise a farmer what fertiliser or combination of fertilisers will give best results on his farm. This survey is based on the results of pasture topdressing trials conducted over the past 20 years in Tauranga County. Tauranga county, situated on the coast of the Bay of Plenty, extends from the Athenree Gorge in the north-west to the Otamarakau valley in ■ the south-east, and is bounded inland by the Kaimai Range. The county is roughly 70 miles long and its width varies from 8 to 30 miles.

With the exception of a large area of swamp country in the Te Puke district, the area generally is undulating to hilly, with gently rolling country near the coast rising inland to a series of low hills. A characteristic feature of the landscape in the Tauranga and Te Puke districts is the series of steep, parallel gorges, which run roughly at right-angles to the sea coast. These gorges are 100 to 200 ft. deep and about 200yds. wide and abruptly break the country into a series of plateaux, on which farming operations are carried out. Near the coast the gorges widen out into valleys which ultimately merge with the rolling coastal country.

Although most of the country near the coast is occupied and has been more or less developed, much of the steeper hinterland is covered with fern and scrub; there are large areas of bush inland and along the tops of the Kaimai Range.

Initial development of the county was slow compared to that in many other parts of New Zealand, partly because of difficulties of access, but mainly because more than half the county was affected with bush sickness, which made sheep farming impossible and the rearing of healthy young dairy stock extremely difficult. Once the treatment for bush sickness was discovered in the early 1930’s farming forged ahead on the bush-sick areas, which were otherwise ideally suited for grassland farming.

Dairying Major Activity The major agricultural activity of the county is dairying—there are over 1100 holdings on which nearly 53,000 cows are milked —which is only to be expected in view of the ideal climatic and soil conditions, and it is reasonable to assume that dairying will always be of paramount importance. The bulk of the dairy production comes from the lower undulating country and drained swamps, although many dairy farms, some with excellent production figures, are found inland on the higher country.

Increase in Sheep Population Over the past few years there has been a marked increase in the sheep population of the county, with fat-lamb production the main activity and the fattening of beef cattle an important adjunct. The spread of ragwort on much of the hill country and inland areas between 1930 and 1940 forced many farmers to go wholly or partly out of dairying into sheep, while the introduction of cobalt topdressing as a remedy for bush sickness made sheep farming possible on areas on which sheep could not previously be run. During the war the shortage of farm labour was responsible for many farmers changing over from dairying to sheep, either wholly or partly. In general, however, the tendency is to run sheep and cattle with possibly dairy cows as a sideline on the hillier inland country, and to run dairy cattle on the easier coastal country. Soils Most of the soils of Tauranga County are pumiceous in origin, having been influenced by one or more of the ash showers that have played an important part in shaping the agricultural destiny of much of the North Island. The two major ash showers associated with Tauranga County are the Kaharoa and. Waihi showers, the former covering the country east of Tauranga Borough and the latter the western half of the county. ■ These two showers have given rise to two distinct groups of soil types; there is a third type, the swamp country of the county. All the pumice country irrespective of the ash-shower group to which it belongs has certain well-defined characteristics. The soil is light and open in texture, naturally deficient in phosphates and organic matter, but free working and well drained. It never pugs up and can be worked even after heavy rains. It warms up quickly in spring, but dries out even in a comparatively short dry spell. Its light texture makes consolidation a most

important factor in pasture establishment and many failures in newly sown grass on this country are directly attributable to seed being sown on a loose seed-bed. Pumice soils are readily wind blown and fairly severe wind erosion has been seen, but once the country is in pasture it is relatively stable. The pumice soils of Tauranga County are ideally suited to grassland . farming, both for sheep and dairy production, and the future prospects of farming in the county are most promising. Waihi Ash Soils The soils derived from the Waihi ash shower are in the western portion of the county. They extend from the Whakamarama hill country to the county boundary at Athenree and include all the points jutting into Tauranga harbour. Although there are several minor variations of soil type within the Waihi ash shower, the responses to topdressing in trials have been relatively consistent over the whole area and it is not necessary to consider these minor variations in detail. The black topsoil which characterises the coastal points varies in depth from 8 to 14in. and is the most fertile in the area. On it are some of the best farms in the county. It is largely devoted to dairying and fruit production. During the past 10 years a number of farms on these coastal points, particularly those near Tauranga, have been cut up into smaller holdings, mostly for the production of fruit. Inland the black topsoil becomes shallower, until in the hill country, the topsoil is a brownish type of sandy loam varying in depth from 4 to 6in. There is fairly marked variation in the type of pasture on the coast and in the hills. The former is characterised by a strong paspalum growth with which is mixed ryegrass, white clover, and minor associated species such as cocksfoot, red clover, and crested dogstail. On poorly managed pastures

paspalum assumes such dominance that other species are suppressed and total pasture production is low. On the better-farmed areas, however, there is a good balance between paspalum and associated species, and a highly productive pasture is the result.

In the higher country paspalum is not so prominent, except on some of the older-established areas, and the pastures tend more toward a ryegrass, white clover, and cocksfoot association, with paspalum, red clover, and crested dogstail as minor sward constituents. Even on this higher country, however, good management and adequate topdressing will result in pastures capable of producing over 2001 b. of butterfat per acre.

Dairying is the main type of farming on the Waihi ash country, particularly on the coastal points and lower undulating country. In the hills the tendency is to run sheep, mainly to control ragwort, with the dairy herd. In the area there are also a number of sheep farms producing good crops of fat lambs.

Most of the coastal country has now been developed, but there are still large blocks of the hillier country awaiting development and carrying at present a covering of bush, scrub, and fern. Much of this country is of good quality and capable when developed of carrying a cow to 2 acres; most of the balance is good sheep country. There has been a considerable area of this hilly country brought into production over the past .10 years and some good pastures can be seen on land that was in fern and scrub only a few years ago.

Kaharoa Ash Soils

The soils derived from the Kaharoa ash shower cover the eastern portion of the county, excluding the swamp areas, and extend from Whakamarama through the Kaimai Range down to the county boundary at Otamarakau. There are several minor variations in soil type, such as are found in the Waihi ash country, but they are of minor importance when considering responses to pasture topdressing.

Kaharoa ash soils are all cobalt deficient to a greater or less degree and all require cobalt topdressing before healthy stock can be reared.

The, topsoil of these Kaharoa ash soils varies in colour from blackishbrown to brown and is similar in appearance to soils of the Waihi ash group. Kaharoa ash soils respond very well to good farming practices and there are many highly productive farms on these soils, particularly in the Te Puke district. The pasture types vary from good paspalum, ryegrass, and white . clover swards on the higher-producing farms to ryegrass, white, red, and subterranean clover, crested dogstail, and cocksfoot on the hillier and more recently developed country in the hinterland.

Most of the easier country is devoted to dairy farming, with sheep being run for ragwort control on many of the larger units. There are also some highproducing fat-lamb farms on this country, particularly in the Paengaroa district. Further inland, though dairying is the most important farming operation, the number of sheep has increased greatly, particularly in the last 10 years.

Swamp Soil The third major soil type found in the county is the peaty loam of the swamp country. The largest single area is in the Te Puke district in the swamp country extending from Papamoa to Maketu. There are many smaller patches of swamp country in the western half of the county in the valleys at the head of the inlets between the coastal points and in some inland valleys and .gorge bottoms.. Drainage of this swamp country is difficult in many cases. The smaller swamps in the western portion of the county have a relatively large area of surrounding hill country acting as a watershed, and the cost per acre of the drainage necessary to cope with this run-off is considerable. In the Te Puke district the drainage of swamp country is complicated by the Kaituna River, which meanders over the area and is responsible for considerable damage when it floods periodically. It is widely accepted that any general drainage scheme for this area is bound up with the control of the Kaituna River, and at present drainage engineers are working on a scheme to control it. Much of the swamp area has been drained and is carrying pastures dominantly paspalum with, in many cases, a good mixture of ryegrass and white clover. Unfortunately, much of this ground contains timber, the removal of which is costly. Even after the land has been stumped and levelled for pasture it is not long before a fresh crop of stumps comes to the surface and the ground has to be restumped. Pasture Topdressing Trials Although there have been various alterations in size and general layout over the past 20 years, the observational topdressing trials conducted by the Department of Agriculture have consisted essentially of measured

plots on which a known quantity of fertiliser is applied, each year. Care is taken to select a farm on a soil type typical of the district under investigation, and, wherever possible, a grazing pasture is selected in preference to one regularly cut for hay or silage. The topdressing plots are laid down on a portion of the paddock away from fences, hedges, tracks, etc., and as even a sward as possible is selected. As it is recognised that clovers are the major plants to indicate fertiliser responses, care is taken to see that there are adequate clovers in the field selected for the trial. Finally, as much information as possible is collected on the past management of the field, particularly the topdressing history. All plots are laid down in duplicate so that they can be a check on each other. One of the early topdressing trials laid down by the Department consisted of 4 plots each 20 x 20 links, topdressed as follows: 1. No manure. 2. Superphosphate, 3cwt. per acre. 3. Superphosphate, 3cwt. per acre, plus 30 per cent, potash salts, 2cwt. per acre. 4. 30 per cent, potash salts, 2cwt. per acre. Half of each of these plots was limed at the rate of from 5 to 20 cwt. per acre, depending on the type of soil and the probability of a lime response. These plots were usually topdressed yearly, the trials being conducted for at least 3 years. Later layouts were modified to suit new requirements. Farmers were no longer content to ask if their land required phosphates; they wanted to know what were the most efficient phosphates and the rates to apply phosphates, potash, and lime. Consequently the number of individual treatments was increased to include

most of the common phosphatic fertilisers. The general layout tended to become increasingly complex, but a greater amount of information was obtained.

The trials were visited by local Instructors of the Department every 3 months and careful observations were made of any responses to various manurial treatments. For uniformity a scale of points was used in which the no-manure or control plot was 0 and a marking of from 0 to 5 points was given to each plot according to the degree of response (1 point, slight response; 2, fair response; 3, good response; 4, very good response; 5, excellent response).

The marking for each plot was amplified by brief notes describing the nature of the response, which was usually seen in improved clover content and growth, better grass quality and growth, improved vigour, or increased palatability.

It was not very long before farmers began to profit from the information gained from these trials. Topdressing was no longer a “hit-or-miss” business and a farmer could order the fertiliser best suited for his own particular soil type.

A number of topdressing trials have been carried on for 15 years in Tauranga County and the table on the next page indicates the results obtained.

The table shows that the principal factor limiting pasture production on all soil types in the county is phosphate deficiency and poor, if any, response, can be expected from any other type of fertiliser unless supplies of phosphate in the soil can be built up to a satisfactory level. Another series of topdressing trials laid down throughout the county has in 12 months given results similar to those shown in the table with even more marked potash responses in most cases. The new trials have not been included in the list of experiments owing to the short time they have been laid down. It should also be noted from the table that application of potash alone gave little or no response. This illustrates that it is useless to apply potash to the soil unless the phosphate content is satisfactory.

The best responses have been obtained when potash and phosphates have been used together. The responses from lime are not consistent, and it is evident that heavy lime dressings are not required in this district.

Soil samples from a number of the experiments have been analysed and a reasonable agreement was shown between laboratory analyses and results obtained in the field.

It is not sufficient to know that phosphates or potash will give a good response. It is also necessary to ascertain if the response is payable, what are the optimum rates of application, and what are the most efficient types of fertiliser to use. 1 Payability of Responses It is not disputed that it is economic to topdress soils of Tauranga County with phosphates. Experiments conducted by the Department and practical farming experience show that it is impossible to maintain adequate pasture growth unless regular phosphatic

topdressings are applied. Farmers’ experiences during the war, especially on the more recently developed country, when fertiliser supplies were heavily rationed gave further proof of the need for phosphatic topdressing. Need for Potash The soils of Tauranga County are showing an increasing need for potash. Potash responses have been obtained on all soil types and are showing up today on country which did not respond to potash 10 years ago. The time is not far distant when the Tauranga farmer will have to apply potash regularly if he wishes to maintain pastures in good heart. Even today there are many instances of farmers who are obtaining a payable response from the use of potash. Though the present price of potash is high, it must be remembered that if only a slight response to the use of this fertiliser is visible, such a response will probably give a good profit. One of the first indications of potash deficiency is a • weakening of white clover and a general unthriftiness in the sward. Though these are often due to other factors totally unconnected with manurial deficiencies of the soil, it would still pay a farmer on this country to suspect potash deficiency whenever the above symptoms begin to show. They appear most rapidly on pastures cut frequently for

hay or silage and some excellent potash responses have been obtained from pastures of this type. 'lt would well repay any farmer in Tauranga County to experiment with potash for himself, particularly on some of his poorer pastures and on hay paddocks. Seldom has potash response been obtained on a night paddock. In the past the general opinion has been that lime is not necessary on the pumice country. Though this may be true in so far as it is not advisable to apply lime until the major deficiencies, which are phosphate and potash, have been 1 satisfied, the judgment is too sweeping. The position regarding the use of lime in Tauranga County would appear to be as follows: — On new country where finance is seriously limited a farmer should make sure of giving his land adequate dress ings of phosphates and, if necessary, potash. This should make first call on money spent on fertilisers. When these fertilisers have been applied consideration should be given to using lime. Over 50 per cent, of the experiments listed on this page indicated a response to lime at some time in their history. The response was not marked or continuous, but it is still considered advisable to use some lime, particularly on the longer developed country. Heavy dressings, however, are not indicated.

Rates of Application

It must be remembered that virgin country in Tauranga County is very deficient in phosphates, which must be applied in adequate quantities to promote the clover growth so essential for adequate pasture production. It has been found that the ideal dressing for new grass on new country is 3cwt. of phosphate per acre at laying down, 3cwt. in the following spring, and a further 3cwt. in the following autumn — 9cwt. in the first 12 months. If blood and bone, is available, a good initial dressing for new grass on virgin country is 2cwt. of serpentine superphosphate plus 2cwt. of blood and bone per acre, followed by 3cwt. of serpentine superphosphate in the following spring. On established older pastures the annual dressing should be between 3 and 4cwt. of phosphate, applied in autumn, or if it is to be applied in two dressings, in spring and autumn. Hay and silage paddocks could have an additional dressing of 2cwt. of serpentine superphosphate in spring when they are closed up. Where the soil is very low in potash the initial dressing should be lewt. of muriate of potash per acre in autumn, followed by annual dressings of {cwt. per acre. When potash deficiency is less marked, annual dressings of {cwt. per acre should suffice. When farmers are testing potash for themselves they are advised to topdress strips down their paddocks with potash at rates of at least lcwt. per acre. It is always of value to leave a small strip in the centre of the paddock untreated with potash so that a farmer can see the degree of response. If 30 per cent, potash salts are used instead of muriate of potash, 2cwt. of the former should be used in place of lcwt. of the latter.

It is not necessary to apply lime in heavy dressings in Tauranga County, except on some of the .inland swampy areas near Tauranga where soil tests have revealed on some of the peaty loam country that lime in rates of 1 ton per acre could be applied with advantage. Elsewhere, it is suggested that lime be applied at the rate of 5 to Bcwt. per acre every 3 years. Types of Phosphate Experiments have indicated that serpentine superphosphate and superphosphate are the most efficient phosphates in Tauranga County. There has been little to choose between these two fertilisers. Careful trials with the slower-acting types of phosphate indicate that they will not give the same response as obtained from superphosphate and serpentine superphosphate and their use is not generally recommended.

On the soils affected by the Kaharoa ash shower cobaltised fertiliser should be. used. It is not necessary to apply 3cwt. of cobaltised fertiliser per acre yearly, but at least lcwt. of cobaltised manure mixed with uncobaltised fertiliser should be applied per acre yearly. Another method is to topdress the farm with all cobaltised fertiliser every 2 or 3 years and use uncobaltised fertiliser in other years.

* In these trials there was an indication of a lime response at some time during the trial, though Mie response was not sustained. t Possible response.

QJ 05 c JC a = 05 ® OS £ a </> o "5? 05 C3j= _ n - E o Is G o ■> a E e District Soil -J Phosphate Potash Lime and a phosphate Ql a Phosphate and -J 0$ potash Lime, phosphate, 1 and potash Soils derived from Waihi ash Points Athenree hill country — 21 M-M 21 31 31* 35* Takawai .. .. ■MMM 2 2 2 1 2 2 3 3 3 3 Main Road, Katikati .. —m 3 3 3 3 3 3 3* 3* Main Road, Katikati .. .. Henry’s Road, Katikati >- Katikati sandy loam — 21 21 1 __ 21 1 31 11 31* 11 Upper Henry’s Road, Katikati — 21 21 M-M — 21 21 35 31 34 31 Wharawhara Road, Katikati . . 1 1 1 — 4 1 4 4 4 Lund’s Road, Katikati .. — H — H 31 31* Matahui, Aongatete .. —M 2 2 2 MM 2 2 2* 2 2* Omokoroa Katikati sandy loam — 21 — 21 ■ 21 21 Te Puna .. .. .. (black phase) MM 2 —— 2 2 25 21 25* 21* Te Puna .... Woodlands, Katikati .. .. Waitekauri sandy — 21 — 21 3 3* loam ■■ 21 21 2 2 21 21 35 31 35 31 Aongatete Aongatete Te Manala sandy loam 2 3 2 2 3 3 2 3 3 4 ’ 3 3 4 4# 3 4* Aongatete — 21 — 21 4 4 Soils derived from Kaharoa ash Omanawa .. ' .. .. —- 2 2 31 41 Pyes Pa .. .. —— 2 t 2 21 21 Oropi Oropi medium loam ■> 31 31 31 31* Papamoa Hills .... 3 — 3 3 3 3 , 3 3 No. 3 Road, Te Puke .. .. —— 2 2 — —— 21 21 3 3 3J 31 Lower Te Matal Road, Te Puke — 21 M— 31 (no potash (no potash Paengaroa medium used) Rangiuru .. .. .. Paengaroa medium used) sand —— 3 M— 3 3 3 3 3* 3* Otamarakau .. .. .. — 2 — 2 2 2 Peat soils Papamoa swamp .. .. Pongakawa peaty — 1 1 — MM 1 1 31 31* Pukehina swamp loam — 1 — 1 11 11 Soils from coastal sands • • Kairua Coastal sand > t 2 — 2 2 21 21 21* 21*