HAWKE'S BAY SOIL SURVEY

Hawke's Bay Herald-Tribune, Issue 116, 2 June 1937, Page 15

HAWKE'S BAY SOIL SURVEY

How Science Has Helped The Individual Farmer IRRIGATION OF THE PLAINS \ PALMERSTON NOETH, June 2. A summary of how the resources of modern soil science have been brought to the aid of the individual farmer; an indication of the main characteristics of the various types of soil; confirmation of the soundness of the principles on which the work is based; and a brief mention of the possibilities of irrigation in Hawke's Bay in which it was considered it might be feasible so to service the western side of the Heretaunga Plains — these were the main features of an address given by Mr 1. J. Pohlen, of the Soil Survey 'Division of the Department of Scientific and Industrial Research, this morning when speaking on the land-utilisation survey in Hawke's Bay at the annual meeting of sheepfarmers at Massey College, Palmerston North.

"I wish first of all to thank you for' the opportunity you have provided to present to you an. aspect of the land utilisation survey of Hawke's Bay and to describe the work done'by the staff of the Soil Survey Department. The aim of the complete survey is to obtain all data in relation to agriculture, and from the picture thus obtained, suggestions may be made whereby farm management and practice may be improved JNTew Zealand is by no means the first country to initiate utilisation surveys. In Ehgland, America and other countries they have been in progress for years, though their aims are by no means the same in eaeh country. In Ehgland the tendehcy has been to show the present use of every acre of land. The general trend of American work is towafds- the production of economio maps for which a tremendous amount of economic data is eollected. Soil surveys have been made in all these eountries as part of the programme. In New Zealand, as will be shown later, we are making such surveys the basis of out investigations and endeavouring to get a thorough knowledge of our soils. We are striving to mako the outcome of all o.ur classes of survey oi practical use to the country. Farming Best Way. "If we could say that it would always be most economical to carry out one specific type of farming in each particular district, if we could say that it would always be most economical to apply certain top-dressings, to grow certain crops or paetures, or to take precautions against certain diseases in one iocality, and to apply certain other topdressings to grow certain other crops in another Iocality, if in other words we could say that for each and every district there was a fixed, most economical type of farming and a definite farm practice which would always be the hiost economical to use, then a farm management survey of each district would euffi.ee to collect all the informntion needed to inddcat© how to favm in the best possibie way. Yet how many of you have found from your own experience that, for example, lucerny will grow on your neighbour's farm, but not on yours, and that superpnoapnata gives excellent responses on one part of your property but not im others. And do you not expiain this by saying tiia'c your country is aixfereni from the pther farmers', that ceri&in parts of your farm are different from other parts? e 4 Every farmer realises that tm> typee of farming he can use and tne tarm pracuices he can employ cannov necessarily be used over the whole oi kis particulftr district, but that they Oepend On the type of land he possessea, whatever modirying i'actors, economic. or ctberwise exert their influence. Tnis principie has Deen known as ia. back as history goes, but it has taken many, many centuries to interpret tuai Knowledge into scientific terms, because until the last decade the scientist has txover been able to classify land into units that are constant, into soil «m.» that can be recognised and distinguished wherever they occur, Many Processes "Many times hae such a ciassiflea- • tion been attempteilj chemists, geolot gists, climatologists, botanists, aud 'geographers a-u atxacked the prulj!lem," and though each met with somo measure of success, they all failed siginally to produce a suitable systeni of : classiiication bocuuse eaeh group of scientists endeavour to interpret the ; soils in terms of its own particular science. They did not realise that the soil was the result of many processes, chief among which were parent rock vegetation and climate, and that there' fore it had to be interpreted in terms of each of these processes before it could be elassified. "It was only a comparatively short fcime ago that these things were recognised and scdentists began to undcvatand that the soil had to be studied 'is uitu' — i.e., as one fdund it in the ilolu, aot as a sample to be examined in a laboratory, not a3 a derivative of 8 tfarticular kind of parent rock, nor yet agaln as a particular medium that xov aioped under different kinds of vege Ution or under certain types of climate They realised that all these things wero hivuived in the devfelopment of the soii aua that the role of each could be ftcugnisea ln the soil profile— i.e., in « section through the soil from the sui xaee of the ground down to the parent iook. And immedialely the soil proniu becanie the natural unit of sfcudj , ctna soil science was establiehod on b. t.ound basis because tlie soils could be clistinguished, elassified, and studied a>;.corumg to their profiles. "The modern methods were adopted by the soil surveys establishcd in Ncvt zealand. Considerable experience wa. garned in the classiiication of soils in vne Rotorua pumice country, in tln Waipa, and in the Ashburton County I't was realised that" for practical rc. sults, agricultural surveys had to bi mude as well— 'i.e., that land utilisa j tion surveys were necessary. We bt

lieve that with our Hawke's Bay survey organisation we lead the way fot young eountries. Types of Soil. "It was deeided tbat tnree main sun veys were to be made and these are the, soil survey, farm management survey and pasture Survey. The object of the soil survey was to map out the different types of said, or as you would probably put it, the different kinds of classes of country. The farm manag* ment survey collects all informa'tion reiating to the types of farm management and farm practice at present being used on each soil type, while the pasture survey maps the various types of pastures. Two Government departments are concerned in these investigations — agricultural and scientific and industrial research. "During his lifetime, man alters the soil somewhat by ploughing and manursing, but the characteristics of the soil type remain sufiiciently distinct for the soil-tvpe may to be accurato for many years. Other things being equal, each scil type should be for practical purposes uniform with regard to top-dress-ing requirements, the crops and pascures it will grow and so on, and it follows that the more we can correlate ;uch factors with the soils — that is, the more we can tie down farm practice to the individual soil types, then li.ie more comprehensive will be the iaformation we can give the individual ianacr about the methods of farming hls own particular soil. Then again, the suitability of . each soil for differ vmt types of farming according to the influence of economic factors such as trcjisport, will give him some definito 'jiformation as to the most economical type of farming he can adopt. JLines of Land tJtilisation. "This brief summary will indicate how the resources of modern soil science are being brought to the aid of tlie individual farmer in Hawke's Bay, whatever his Iocality and whatever his soils may be, and it is not difficult to *ee also how the information being eollected will indicate the directioTs along which future land utilisation in Hawke's Bay should proceed. "It has been described how the socls are elassified according to what is "vermed their soil profile, which is sim^ly a vertical section of the soil from .iie surface of the ground to the parent rock. In a detailed survey such is now being carried out on tho Hastings orchard area, each ?udividua) soil i»rofile is mapped as a soil type as far rm possible, but it" may be neeessery to group together several profiles differing but slightly from one another. In a regional soil survey like the present one, over all Hawke's Bay, the soil types mapped are usually groups of soil profiles of very similar nature with the same general character. "The maan characters of the soi> profile may be divided into two broad groups, physical and chemical. The main physical characters are texture and structure. The coarser particles in the soil weather and decompose into smaller ones and the finer particles — the clay — under the influence of rainfall are washed or lcached down. We refer to the zone from which material has been removed as the A or leached horizon and the zone dn which the ma^erials have been re-deposited lowedown as the B horizon. "It ia general in older soils to have a sandy top-soil from which clay and chemical constitnents have been washed out and a heavder sub-soil in which the clay has been re-deposited. A heavy aub-soil of this nature renders the drainage imperfect because the water cannot freely drain away. Blue, green and grey colours are produced in these poorly-drained soils by reducing processes, while in well-drained ones the predominafcing colours are yellow golden or red, depending to some extent on the degree of hydration of the iron, which in tnrn may be related to the rainfall. More complex colours are produced in soils that are seasonali? water-logged. Clay Soils Biffer. "A clay soil is not necessarily a poorly-drained one," he pointed out, "as irnigators haVe found to their cost, because certain clays have a high-ly-flocculated nature which is expressed in a well-developed crumb structure, and this allows a high degree of aeration and well-drained condition. ln" Hawke's Bay the leaching or washiug out of chemical constituents, the plaut foods, lime, phosphate and potash is very noticcable on old»,r soils, although it has not proceedsd £o the same extent as in North Auckland and other high rainfall areas, e.xcept perhaps in the caSe of limestone soils, in which a considerable depth ef limestone must have been dissolved and removed to yiold the deptb of /esidual soil now present. "Each soil is the expression of its parent rock, climate and vegetation. The soils of Hawke*s Bay are relatively young and are thereforo strongly in-

fluenced by their pa.ent rocks. Eorest soils have temporariiy a high fertility, whale fern or scrub joils are naturally not so fertile. The rainfall with its distribution over the year is responsible for the texfcurai, differentiation of the profile, but its action is modified by topography and parent rock. On flats or gentle slopes rainfall has dts greatest, effect but, where the slopes are steep and the run:off greater, the textural profile is less well developed. When the parent rock is coarse-grained, as in sandstone or conglomerate, .finer constituents are readily removed; but, in a fine-grained parent material such as mudstone, the downward movement of clay is rendered more difficult and the soil long remains immature. On steep slopes, too, slipping, particularly in mudstone soils, is eonstantly removing the more developed profiles and exposing the parent rock beneath so that these soils remain immature and, consecruently, fertile. Effect on Plant Nutrition. "As the plants depend largely on the finer material for taeir food fupply, it will be seen that wexi-developed profiles are oharaeterisfic of poorer and mfertile soils because tfie ciay and plant nutrients have been removed out of reaeh of the roots oi the pasture. "This brief sketch of the soil characters is perhaps suffieient to illustrate how the pedologist or soil surveyor is able to distinguisli a soil profile by examiing it with an ordinary augur to a depth of three feet and recognising its variations in texture, colour, moisture, structure, etc., as you go down through that three feet. The profile is the final eriterion which distinguishes the soil type. The pedologist is trained to observe faetors associated with eaeh type, and h'is ingenuity is always being called upon to lieip him to map rapidly. He finds that soil types are topographic units, and takes into account the contour, ruggedness, steepness and so on of the hills, or the slight depressions of the flat and innumerable minute differences m the topography undetected by any but the skiUed observer. He sees characteristic pasture associations with. each soil type, or perhaps c certain grass or weed that grows on one type and not on others; he notes the occurrence of springs, of bush and its composition, and by a number of distinctions he comes to fecognise the soil type by the look of it. "It is incumbent on him, however, to map soil types which are of economiic use to the agriculturist, and he therefore occasionally questions farmers to find out whether, m their opinlon, the soils do ehange with the types ne has mapped. > It is weli known that the farmers, from , long experience in their Iocality, can of ten detect the diff'erence in their, district and if their opinion differs from that of the pedologist the latter must check his work and ensure that his mapping ±s correct. To assist him he will seek information from the farmer as to the carrying capacdty, response to fertilisers, etc., in different parts of the farm. Maps Checked Over. "Before the final map is prepared the field maps, are checked over with the air maps, and as the* topographic boundaries are often soil boundarids, the soil map can be aceurately completed, though this ia rather putting the cart before the horse. Accurate topographic maps shculd be made iu advance of the sodl survey. "The soil isurveyor 's investigations. do not rest with the completion of his map. Each soil type is further examined in the laboratory, and typieal soil samples from different depths on each type are sent to the Dominion analyet and the chemucal laboratory of the Cawthron Institute. Here the soils are investigated from the chemical point of view, and from the analyseS considerable information is gathered about the fertility of the soil. The soliddty, available potash, phosphate. ete., are determined. At Cawthron Institute the textures of the soils, as determined by tte pedologist in the field, are checked and the amount of sand, silt and clay in each eample is determined. Biut I shall not expiain now all the technieal uses to which this information is put. "It is not possible to say very much about the actual progress of the work. The main result at the present time is che confirmation of the soundness of the principles on which the work is based as more and more data ds eollected. The advanced nature of the Hawke's Bay utilisation survey has already been emphasised. In any pioneering work so comprehensive in its aims, one must expeet to encounter difficulties which at first sight appear to be almost insuperable. So, too, at the begdnning of this research work, although the main lines along which information could be correlated with the soils had been clearly visualised by Dr. Grange, many practical diffieulties were encountered by the technologists in adapting thedr information to colleet the required data. Much Work Involved. , "Originally it was planned to complete the work in a little over 12 nionths, but it was soon realised tbat the soil variations were very numerous and that, although such rapid mapping was valuable for general land-ufcilisa-tion purposes, it was not fulfilling the primary object of the work, that of assisting the indiyidual farmers. It was consequently deeided to slow down the work considerably. We have iudeed been fortunate to obtain the cooperation of the farmers and business people an Hawke's Bay, and it is generally recognised that time is necessary to collect the volume of intormation required over the 5000 square miles in the province. "The bulletin on Central Hawke's Bay, which will probably cover the area from Tongoio to Pourerere S.D.'s on the coast and westward to the ranges, is being compiled, but occasionally some criticism is expressed because the results have not been published. A recent instauce of this occurred in connection with irrigation of the Heretaunga Plains, when it was stated that nothing appeared to have been done. Tliis instanco serves to emphasise the volume of work already completed and the amount yet to be done, before coustructive suggeRtions can be made. "The possibilities of irrigating not only the Heretaunga Plains but also the Takapau Plains are being investigated. The soil map of the Heretaunga Plains has been largely completed by Mr. Hughes, and the main area suitahle for irriga-

tion appears to he the western part of the plains, although more detail- '• I ed w\.k is swlll required there. ' This area falls in heighi; from over 200ft. in the north to 38ft. at Pakipaka. "It might b© posBibxe to irrigate tlie Pakipaki district artesian water and the rest by water from the Ngaruroro river, but the engineering side of this has to be investigated by'the Public Works Department. The soil survey has shown that, cast of the irrigatable country are areas of rieh fertile soils which might very easily be subjeeted to high-water table, and of eourse further investigations are necessary in connection with this and very decidetily with regard. to the drainage of surplus irrigating waters. "You will readily see from the maps the amount of work that actually has been done, but more data is required wJLth regard to levdle, jSoils, watertable and drainage, source oi water and quality of water before a constructive scheme can be suggested. And this, roughly, is the positdon with the whole of the Hawke 's Bay utilisation survey at present, A good deal of work has been completed, but this has to be analysed and more data has to , be eollected before the bulletin is published. "Eor this reason it is not worth while elaDorating on the spedal inves- : Cigations which are being carried* out in conjunction with the general, programme already outlxned, and in conclusion I 'should like to quote the words of the Mayor of Dannevirke last week when he extended. a civie welcome to the delegates of the New Zealand • ' Farmers' Undon: 'I am firmly convirieed,' said the Mayor, 'that before this, , generation has passed away almosV every science will be- made use^bf fi. assist in a more economic and efficient production of the world 's foodstuffs. ' ' "The Hawke's Bay land-utilisation . survey is a major project which ,it is hoped will assist in this direetion. Although tie work will ultimately benefit the business people and the country ; as a whole, still it primarily benefits the farmer, and we expect those of you who belong to Hawke 's Bay to discuss . . the lectures that you hear thiis morning in your respective districts so that we shall continue to receive the co-opera-tion of the farmers. Those of you Who come from other provinces will perform a valuable service if you make known in your districts the significance of the work in Hawke's Bay, so that when the land-utilisation surveys are com- • menced there they will meet with readr co-cperation and assistance." The address was illustrated by maps 1 of land-utilisation surveys in England ' and America; maps of the soil types on the Heretaunga Plains and neighbour* j ing hill country; an air mosaic map of the area roun'd Puketapu; and lantern slides of various . soils in the Hastings area and Wakarara district.