FARMING IN NEW ZEALAND

New Zealand Journal of Agriculture, Volume 69, Issue 2, 15 August 1944, Page 121

FARMING IN NEW ZEALAND

Climate and Topography

By-

MARY AITKEN,

Fields Division, Christchurch

Climate, topography, soil fertility, and markets have been the determining factors in the development and distribution of the Dominion’s systems of farming. This article describes briefly the climate and topography of New Zealand and their bearing on the dominance of pastoral farming.

CLIMATE. THE extremely favourable climate of New Zealand to a large extent accounts for the high agricultural productivity of the country. Owing to its. geographic position the winds .. that reach New Zealand are moisture bearing. The main rainfall division of the country is east-west. The high relief accentuates the rainfall on the west coast, while in the east it gives rise to large areas of relatively low rainfall. The country benefits from an adequate rainfall (Fig. 6). In most of the habitable parts it is from 30 to 75 inches. The efficiency of this rainfall is reflected in the luxuriant nature of the forest cover and the abundant growth of grass. In the North Island the growth of grass continues for the greater part of the year. In the South Island growth is checked during the winter months. In elevated regions and other areas which are little settled the rainfall is over 75in. This precipitation from an agricultural point of view is excessive. In parts of the tussock areas, however, rainfall borders on deficiency. In Central Otago the rainfall is from 10 to 15in. In the semi-arid areas the landscape takes on a dry and barren aspect. There is little seasonal change in the appearance of the vegetation cover. In general rainfall is adequate and evenly distributed throughout the year. The number of days on which rain falls varies throughout the country (table X). Even in the areas of heavy rainfall the number of rain days is limited. There is no month with less than 1.2 in., except in Central Otago.

TABLE X.—AVERAGE ANNUAL RAINFALL.

Average Annual No. of Station. Rainfall. Rain Days. Auckland 45 184 Napier ,35 113 Wellington .... 47 166 Nelson 38 118 Hokitika 114 187 Christchurch . . 26 ‘ 126 Dunedin 40 161 Invercargill ... 45 194 Clyde 15 - 77

There is, however, in certain regions a marked seasonal concentration of rainfall.. In North Auckland there is a definite winter maximum of rainfall. This tendency is dominant as far south as Kawhia on the west coast. On the east it extends as far south as Banks Peninsula. On the west coast from Kawhia to Fiordland there is a tendency to a maximum in October and a minimum in February, with a secondary maximum again in May. In dry areas, to the east of the ranges, particularly in Central Otago, there is a concentration of rainfall in the summer months. In these interior situations ? climatic conditions resemble those prevailing in continental areas. All areas east of the ranges, especially those in the South Island, are subject to strong north-west winds. These are hot, dry winds, which

often blow continuously for several days in the summer and autumn months. In the low-rainfall areas these drying winds reduce further the efficiency of the rainfall. The natural vegetation in these exposed areas was the tussock formation which was almost completely devoid of the larger trees. Rainfall fluctuations from the normal are important for agriculture, as they may determine the success or failure of crops. Twice in Canterbury and Marlborough since European occupation the rainfall record has fallen to half the amount normally received. There is no record, however, of two continuous months without rain. Rainfall variability is highest and most serious in the areas of heavier precipitation. In regions of lighter rainfall a considerable departure from the average may not be serious. Rainfall is most reliable in those areas which receive rain from the westerlies, i.e., Taranaki, the West Coast, and parts of Southland. The suitability of Taranaki for dairying is doubtless related to this fact. The climate of New Zealand has then a well-distributed and reliable rainfall, falling on a limited number of rain days. It has also a high number of sunshine hours (table XI).

TABLE DURATION OF SUNSHINE PER ANNUM.

Duration of Sunshine in hours. Auckland - 2033 Napier 2416 Wellington 2050 Nelson 2510 Hokitika 1918 Christchurch 1967 Dunedin , 1711 . Invercargill 1626 Lake Tekapo (Mackenzie Country) .... 2409

Nelson receives the longest duration of sunshine with 2510 hours annually.

Temperature Station. in deg. F. Auckland 59 Napier 56 Wellington ....... 54 Nelson 54 Hokitika 52 Christchurch 52 , Dunedin ............... 50 Invercargill 50 Ophir (Central Otago) 51

TABLE XII.—AVERAGE ANNUAL TEMPERATURE.

Even Hokitika with 114 in. of rain receives 1918 hours of sunshine. This frequent alternation of heavy rain and bright sunshine distinguishes the climate of New Zealand from other parts of the world with a similar type of climate. Brilliant sunshine : and sometimes strong wind after rain permit the rapid drying of the ground surface. There is a definite range of temperature with latitude (table XII). The average annual temperature varies from 59 deg. to. 50 deg. In the north citrus fruits and tung plants can be grown. Seasonal ranges of temperature are least in the north, the difference between the hottest and coldest month being 12.5 deg. in the far north.

coastal strips and fiver valleys. Such lowlands , are of limited extent and are not continuous. Other areas of flat land occur at higher altitudes in elevated inland basins. These lands, however, are outside the denser areas of settlement. Much of it, though occupied, is still unimproved land. Thus it is seen that the flat land in New Zealand is but' a small proportion of the total area. The. chief areas of lowland in the North Island are as follows: 1. The Manawatu - Horowhenua Coastal Plain: The Manawatu Plain stretches from the Manawatu Gorge to the coast. From the gorge to Palmerston North the plain slopes steeply, but between the town and the sea the slope of the plain is more gradual and the river follows a winding course across it. This part of the plain is separated from the sea by a line of

sand dunes. The rainfall on the coastal belt is sufficient for dairy farming on the light sandy soil. Southwards the coastal plain becomes narrower and is then known as Horowhenua Coastal Plain, as it is largely contained within the Horowhenua County. This plain consists of a series of terraces along the foot of the highland. On its outer edge it is fringed by sand dunes and swampy hollows. These hollows, many of which were formerly covered with Phormium flax, are numerous in the vicinity of Levin. 2. The Taranaki Plain: The Taranaki Plain is an elevated plain ending at the sea in cliffs. It is cut by the rivers which emerge from the hill country. At the present level of the rivers there are small areas of plain lying at a lower level than the general elevated surface of the country.

In the far north only one ground frost per year is experienced, whereas Ophir (Central Otago) has a range of 25.4 deg. and 192 ground frosts per year. There is also a marked daily range in temperature in both summer and winter. In conclusion, the following outstanding features of the New Zealand climate may be noted: Winters are mild, there . being no continuous snow cover on the low country. Stock do not need to be kept under cover during the winter months, but in exposed positions the provision of shelter is beneficial. The rainfall is adequate and evenly distributed throughout the year. It falls on a limited number of rain days. There is thus a long duration of . sunshine hours. The atmosphere is well washed, clear, and free from dust. TOPOGRAPHY. New Zealand is largely a mountainous country (Fig. 7). Less than one quarter of its land surface lies below the 650 ft. contour. It thus presents a marked contrast to eastern Pacific countries, which have large areas of land below this level. The two islands of New Zealand are divided into eastern and western regions by the main mountain axis, which runs from Fiordland in the South to East Cape in the North Island. Although the mountain barrier is of little use for an intensive type of agriculture it is important as a collecting basin for rainwater, which may be used for hydro-electricity or irrigation. On either side of the mountain ranges only relatively small areas of flat land occur. These are mainly

4. The North Auckland Peninsula: This unit includes the North Auckland Peninsula and the smaller Coromandel Peninsula. The surface of the latter is mainly in native bush and scrub and is of little use for farming. The country of both these areas is complex in character. The chief areas of flat land are those along the rivers in the coastal areas. The region is mainly an upland of low elevation, generally below 600 ft., but there are several peaks rising to 1000 and 2000 ft. The region consists mainly of soft rock uplands forming undulating country. There are also outcrops of resistant rocks, chief of which are the volcanic rocks forming outstanding and resistant masses. The coastline of the peninsula is often irregular, there being long indented inlets with . extensive estuaries and mud flats. There are also large areas covered with sand dunes, e.g., those along the Ninety Mile Beach and in the far north. The chief areas of lowland in the South Island are as follows: 1. The Nelson Lowland: This lowland consists of a v-shaped area of land. It is divided into two sections separ-

acteristic of the plateau as a whole. Much of the country surrounding the plateau provides good grazing, tongues of land such as the Rangitaiki Valley penetrating inland to the plateau. 3. Inland Wanganui - Taranaki Hill Country: This tract of dissected plateau country fringes the western boundary of the volcanic plateau from which it stretches to the volcanic cone of Mt. Egmont. The hill country surrounding it is composed of soft rocks. The highest ridges are those further inland and overlooking the volcanic plateau. In the east it rises to 3000 ft., while in the west it is under 2000 ft. From .the highest ridges there is an even slope of the land towards the coast. The whole plateau has been intricately and deeply dissected by streams. The ridges between the stream valleys have sharp crests and steep-sided slopes. It is important to note that this area of weak rocks and steep hill slopes is also one of high rainfall. The soil was formerly protected by a dense forest cover. Today much of this type of land has been cleared. In places it is used for the grazing of stock; in others it is reverting to second growth. ;

3. The Wairarapa Lowland: This lowland is a long valley running parallel to the high country and separating it from the coastal hill country. It is part of the gravel-filled lowlands which stretch northwards to Hawke’s Bay. 4. The Heretaunga Plain: This plain is the most extensive area of flat land on the' east coast. It is roughly triangular in shape and is formed of alluvial sediments deposited by the rivers which cross the plain. Since the earthquake of 1933 much land has been reclaimed from the Ahuriri Lagoon. 5. The Waikato - Thames Hauraki Plains: These plains are composed mainly of volcanic sediments derived from the plateau. It may be mentioned here that the plains of the North Island are usually composed of finer sediments than those of the South. A considerable portion of the area was formerly swamp. Where this has been drained it now makes good farming land. This lowland area is separated by a low range from the small disconnected plains of the Bay of Plenty. In the North Island the main units of the high country are as follows: — 1. The East Coast Ranges and Hill Country: These mountains extend from Cape Palliser to East Cape, a distance of some 350 miles. Throughout its southern section the ranges are narrower than they are to the north of the point where they are cut by the Manawatu River. From this river gorge they widen out, the Kaimanawa Range extending westwards towards the volcanic plateau as a wide belt of rugged mountain country. On the eastern side of the main range there is an extensive belt of hill country stretching to the coast both to the north and south of Hawke’s Bay. The northern ridges of this soft-rock hillcountry lose elevation seawards. The slopes facing inland are steep, while larger and more gradual slopes face the coast. In these valleys there are few large rivers and it is only in their lower valleys that there are any areas of flat land. The largest area of flat land is the Poverty Bay Flat formed by the valley of the Waipaoa River. To the south of Hawke’s Bay the main ranges are usually separated from the coastal hill country by the chain of gravel-filled depressions referred to previously. 2. The Volcanic Plateau: This plateau occupies the greater portion of the middle of the North Island. From it radiate the main systems of river drainage of the North Island. The plateau is built of volcanic material, its surface being relatively even, but often broken by volcanic cones and irregular ridges. The greater part of the plateau surface is unproductive and unsuited to agriculture. Farming has been successful in a few areas but is not char-

ated from one another by the Moutere Hills, which are a low upland. The valley plains of the Motueka and Waimea Rivers to the east and west of the hills respectively, comprise the best agricultural land, the higher land between them being poorer country. 2. The Marlborough Plain: This plain is bounded on the west by the mountains extending to the sounds country. Towards its upper end the valley plain of the Wairau is built of coarse sediments, but nearer the sea the plain is composed of finer sediments. The lower sections are flatter and were formerly swampy. 3. The Canterbury Plains: The largest unit area of flat land in New Zealand is formed by the Canterbury Plains, stretching from Amberley to Umaru. It widens in its middle zone to a distance of 40 miles and narrows towards either end. The plain consists of an immense thickness of gravel deposited by the rivers. These gravel deposits are thickest and coarsest close to the mountain upland. In general they are covered by ,a layer of fine, material sufficient in depth to provide fertile soils suitable for the production of cereal and forage crops and of good sheep-farming, pastures. Across the surface of the plain the main rivers have formed wide river-beds over which they are constantly changing their course. Around the coastal margin of the plain are fringes of finer sediments which also occur in the slight depressions between the river-

beds. ' Around Christchurch there were areas of swamp. These have now been drained and form good heavy land. The remaining type of land on the plains is a narrow belt composed of beach ridges of sand dunes extending from the mouth of the Waipara to Banks Peninsula. 4. The Southland Plain: The Southland Plain is formed of extensive deposits of gravel and silt. This is a highly productive region with high returns per acre, but its high productivity is possibly more closely related to its climate than to its soil formations. 5. The Westland Plain: This consists of a narrow and discontinuous coastal plain stretching along the western side of the Southern Alps. The lowland' area often extends inland as along, the valley of the Buller River. The main areas in the South Island high country are as follows :— 1. Fiordland: This area covers the southern and western part of the island. It is mainly mountainous country with flat-floored valleys. Much of the land is over 5000 ft. It is agriculturally unproductive, its - greatest value lying in its scenic attractions. 2. The South Island High Country and Foothills: This high country stretches from the northern boundary of Fiordland throughout the entire length of the island. The ranges are highest along their western margin, their bush-covered slopes rising steeply from the Westland Plain. On

the tussock-covered area on its eastern side sheep may be grazed almost ■ up to the snowline in the summer months. On the eastern side there is a belt of foothills country of lower elevation than the hard rock. Highland: Hill country ridges extend to the coast in Otago and Southland, where they alternate with areas of softer rock and river valley plains. Banks Peninsula forms yet another isolated area of South Island hill country. It is separated from the main belt of hill country by the Canterbury Plains.’ This peninsula consists of an old volcanic cone which has been dissected and worn down by erosion. On its outer side slopes are long and gentle till the summit is reached. The inner slopes facing the harbours of Akaroa and Lyttelton are much steeper. Throughout the hill country there is little even land. Although this land is occupied it is still largely unimproved land. The tussock-covered plains of the Mackenzie Country provide a good example of this class of land. Other areas of flat land, a proportion of which is cultivated, occur in the Waikari, Culver den, and Cheviot basins- of North Canterbury. 3. The Central Otago Ranges and Plains: The Central Otago ranges are of lower elevation than those of the high country. They are separated from one another by basin plains which lie at an elevation of from 1000 to 2000 ft. They have steep, sharp faces overlooking a depression, while their back slopes are inclined at a lesser angle towards a neighbouring depression. As Central Otago is an area of low rainfall a great deal of land on river terraces is 200 to 300 ft. above the water table. As the present course of the rivers is at a lower level than the flat tops of the surrounding terraces the irrigation of this land is made difficult. It would entail the building of dams and the digging of water races. Factors such as these - have operated against irrigation in the drier areas. Moreover the amount of land suitable for irrigation is only a small proportion of the total area.

FENCING MATERIALS ' For estimating requirements of fencing material the following figures will be found useful: — Plain Wire ' Gauge. Yds. pet cwt. No. 8 566 No. 10 882 No. 12 1333 Barbed Wire No. 12 (3in. barbs) 450 No. 14 725 The “effective” length per cwt. is often quoted and is the actual length of fencing that 1 cwt. of wire will cover, allowing for bends, waste, etc. The effective length of No. 8 wire is 484 yds. per cwt.