METEOROLOGY IN RELATION TO FARMING.

New Zealand Mail, Issue 1775, 14 March 1906, Page 61

METEOROLOGY IN RELATION TO FARMING.

The following paper, which was read at the last Agricultural Conference in Wellington by that able original worker, the Kev. D. C. Bates, F.R., Met. ®., was recently issued as "Bulletin 9” .of the Department of Agriculture—Divisions of Biology and Horticulture: Meteorology is the science which seeks to explain the phenomena of the atmosphere; and one branch —the geographical application of meteorology, called climatology—is of especial interest to farmers, because it deals particularly with those atmospheric agents which have the greatest influence upon organic life. The relationship of climate to the life of plants and animals is at once direct, constant, and simple. Plants derive their food more or less from the air as well as yie soil; and atmospheric conditions also are of paramount importance with regard to the germination, development, and maturation of the crops as well as the health of the live stock of the farm. The weather immediately concerns all agricultural operations, and assuredly there is no subject more constantly m the mind of the farmer than the possible effect of the changing weather upon his main interests. It is almost a maxim that "climate beats culture/* and some or the best authorities in England have said that, in a good season the produce of the farm is double that in a bad one. Climate is the sum total of the weather. while weather may be described as a temporary disturbance of the climatejust one phase in that succession of pn&* nomena whose complete cycle recurs with greater or less uniformity every year. The first requirement in the description of any climate is accuracy in the measurements of all the climatic elem.en.es. Eor this purpose it is the aim of meteorology to systematise and give numerical expression to the cliniatic agents, v ague generalities must give way to scientific measurements of every climatic featuie %hich is capable of comparison between ’ different places and seasons’. We will give examples of tlie application of climatologv and' briefly indicate some of the bearings of the science. 1. The months of October and December, 1904, were excessively wet. and during the summer thundery conditions were unusually prevalent. This weather, so favourable to fungoid growths, sufficientIy accounted for the serious nature of the outbreak of the potato-disease, and, should a similar season recur timely and effective measures can be taken ro prevent loss of the crops. . , 2 Again, the British Meteorological Office has shown how the rami all o. the previous autumn has, more than that of other periods, a wonderful effect upon the yields of wheat in the following year the wheat-yield going up ae the ramiaii is lower —less rain more wheat and lismg and falling in fairly close relationship, ©very inch of rainfall being accountable for a drop in the yield of wheat ai me rate of a bushel and a quarter per acre. In a rough Avay I have already found it true in New Zealand. Our generally light autumn rainfall in 1904 had, I may point out, more effect on our late harvest than the winter and heavy spring rains. We had generally a dry autumn in 1905, and should therefore have good yields in 1906. 3. Another instance: Cape Colony has a dry summer, and the neighbouring colony, Natal, a wet one. In these respects these countries resemble Spam and China and experience has recently proved that -while Cape Colony can grow the grapes of Spain to perfection, the A\ec summer of Natal suits the tea-plant of China. 4. Ohs more example; The central parts of the United States were desert until it was found that wheat grew m a similar climate in the heart of Russia. That Durum wheat ay as tried in America, ' and noAV. Avhat Avas once an arid desert is annually producing millions of bushels of good milling Avheat. In NeAV Zealand Ave may divide our climate under four geographical regions, according to the North and Soiwh. Islands and from the main ranges which give and Avestern aspects. There are very marked differences in these four climatic regions, Avhieh Ave Avill not uoav discuss beyond remarking that the land on the “West Coast precipitates t}ia moisture as it comes off the Tasman Sea Avith the prevailing westerly winds, and the fall is much greater than on the East Coast—thus Hokitika averages 117 in of rain per annum, Avkile Central Otago has only 17in. In the North Island, Taranaki averages about *soin, but Napier only SlSin. Diagram No. 11. shows the average monthly rainfalls at Hokitika, Wellington, and Canterbury. These three places are differently situated Avith regard to mountain ranges. Wellington, in the North. Island, is but little exposed to disturbance of its climatic conditions by mountains, and its records present a fairly good average for the country. Hokitika lies on the western side, at the foot of the Southern Alps, but the Canterbury Plains are on the eastern side of this lofty range. The westerly winds meeting the ranges on the West Coast are arrested, and their _ moisture precipi- - t-tpfi in larger quantities—thus m October /hen westerlies most Pfe/ail the rainfall is usually the highest at Hokitika while in Canterbury the monthly average is actually the lowest . m the year The reason is. that the winds are f£st drained of their moisture and pass ~ ■mnriTvf-fl'ms’ they are then Avannover the mountains, « dAKcend ? 0 d ti irs. rain they cause evaporation. The aryr* hot north-Avestere of Canterbury ai e g erally described as foehn AVinds, and found! in all mountainous cotin tries. Climatology is concerned with (1) the temperature of the air and soil; (2) the moisture of the air as vapour, cloud, and precipitation; and (3) wind, or motion of the air in storm, etc. Temperature is the most important of all the climatic

•Mean from ten stations.

elements, and scientific observations for a few years afford good averages on which climatic comparisons rtuxy be made. All that is necessary for climatological purposes is to have good maximum and minimum thermometers, exposed in a uniform manner —that is, in a Stevenson screen.” The temperature of a place is influenced and modified by different soils and subsoils, the neighbourhood of swamps, forests, and mountains, etc. Temperature decreases upwards at the rate of about ldeg. Falir. for every SCfift of elevation, and about a degree for about seventy or eighty miles southward. These rules are subject to great exception—e.g., there frequently occur '‘inversions cf temperature,” when it is warmer above than below; tlius we get frosts on the valleys and flats, and even the lower parts of shrubs and plants will sometimes be injured while the upper leaves are free from its effects. On some days it will also happen that the South Island will be warmer than the North. In Phillips’s seif-registering thermometer for heat the index is formed by a small portion of the mercurial column, separated from the main thread by a minute air-bubble; this portion is pushed on before the column when the temperature rises, but does not return when it falls. The detached position of the column therefore rests at the extreme position to which it has advanced, and the end of it farthest from the bulb registers the highest temperature which has been attained. The instrument is set by holding it bulb downwards and gently tapping the lower end so as to allow the detached portion of the mercury to approach the rest, from which it remains separated by the air-bubble. Rutherford’s self-registering thermometer for cold contains a spirit in which there is an index immersed. When the temperature falls the spirit-column decreases and draws the index along with it; but on rising again, the spirit passes the index, leaving it at the lowest point to which it has been drawn, the end farthest from the bulb thus registering the minimum temperature. The Stevenson screen is a box with double louvered sides and a bottom open enough to allow a free current of air. The internal dimensions of the box are —length 18in, width llin, and height 15in; with a double roof, the upper one projecting 2in beyond the sides of the screen It is mounted on posts so that the bulb of the lowest thermometer is •pst 4ft above the grass The door must open to the south, so that the sun does not shine on the thermometer when the door is opened. The screen should never be placed in the shade or within 10ft. of a wall. The screen must be. painted W With regard to temperature, another matter believed to be important to agriculturists is "accumulated temperature. Plants store up or accumulate energy or

matter from the air and soil. A temperature of 42deg. Fahr. is regarded as the neutral point for A'egetable growth. Below this temperature growth in plants does not usually take . place, Avhile any degrees of lieat aboA-e it account for devekmment. A certain amount of accumulated heat is needed for .growth, and lastly, a final summer height of the thermometer is required to thoroughly ripen the crop. Wheat needs, according to English computations, an accumulated temperature of near 2000 "day degrees/ Avhieh are reckoned above 42deg. Falir., but oats require less to bring them to perfection. . „ n . Dr. Bnclian found that m Scotland Avheat only ripened Avhen the mean temperature during the summer months Avas as high as 56deg. Falir., and .that the chief difference between Avheat and oat crops Avas not so much that tho latter required a smaller total of heat to ripen it as that the former reqiiired greater concentration between the times of floAvering and ripening.

Now for a few remarks about the moisture of the air. Water is the lifeblood of the atmosphere, penetrating every part of it and accounting for its energies. Water is found in three different physical states—gaseous,. as vapour; fluid, as Avater; .and ©olid, as ice. Condensation of the Avatery vapour takes seA r en interesting forms, in deAV, fog, mist, cloud, rain, hail, and snoAV. Whatever condenses or falls on the ground is called "rain/* and it has been measured in four ways:

1. The rainfall has been measured Avith a foot-rule dipped into a catchment vessel, or from the rising of a float. 2. The rainfall has been Aveighed. The area of a small vessel being regarded as a fractional part of an acre, multiplying the Aveight of the fall collected therein gave it as a fall of so many tons to the acre.

3. Another way was to have the funnel of the gauge of such a diameter that a pint of water was equivalent to an inch of rain. This also involved calculations for smaller quantities; and so—4. It was lastly found better to have the area of the gauge just ten times greater than the area of the measuring glass. Thus, if area of funnel is 20 square inches the measure will have an area of 2 square inches. If an inch cf rain fell into the gauge a measure lOin in height would be required for its measurement; and lin on the measure would give l-10in of rain; and a tenth of that l-100in, or a "point of rain.” Half a point constitutes a day with rain, and is a measurable quantity; but if only half a point (.OOoin) is measured it is put down as a whole point, .Olin. One inch of rain equals 4f gallons to the square yard, and 22,i635 gallons, or 3630 cubic feet to the acre; and this quantity weighs over 101 tons to the acre. The size of the gauge is not important. At Bothamstead, in England, one gauge

with an area two thousand times greater than another did not at any time differ more than 5 per cent, from the smaller one. Ganges of sin and Bin in diameter are in general use in the English-speak-ing world. Rainfall is usually registered at 8 or 9 a.m., and the probality is greater (16 or 15 to 8 or 9) that it actually fell on the day before, and so it is by the rules recorded to the previous day. A matter I have advocated for some time is bringing our rainfall returns into correlation with the seasons. Agriculture is chiefly interested in the season with its culmination in the harvest, and from the end of one summer to the end of another is a more natural division than the rule of dividing the yearly returns at the very height of summer (or winter at Home), at the arbitrary time of the 31st of December. Different countries have different seasons; but the amount of the annual rain would still have the same theoretical interest for comparisons, and the practical application would be a distinct gain to agriculture. Such a system would, moreover, bring meteorology into touch with farming, and show its utility and relation to production. Lastly, with regard to atmospheric disturbances, our climate is a variable onechanges are frequent, but never really sudden. The motion of the air is related to its barometric pressure —beloxv the normal it is the depression, or cyclone, and above it the high pressure or anticyclone. Roughly speaking, 30in is onr normal, and below this the winds revolva in vast circles 500 miles and more across. The word "cyclone/ 5 from cyelos, a circle, has unfortunately become associated generally with the intensity of tropical hurricanes. This intensity of force, however, is spent after the depression spreads itself out in high latitudes. In our hemisphere the winds of a depression move around the centre of lowest pressure in a direction with the hands of a watch. For example, let us consider a case -when the centre of the depression is over Cook Strait, then in the North Island the winds will be westerly, while easterly winds prevail in the South. Off the east coast they will be northerly with a falling glass, and over the Tasman Sea the winds will come from the south, and the glass will rise as the cyclone moves away to the eastward. In low pressure the winds have an upward tendency, and the rising moist air is cooled, so that the vapour is discharged as rain. Another very frequent cause of our heaviest rains and strong sonth-east winds is the mixttire of the warm and vapour-laden airs of a northerly depression with the cold airs at the edge of an anticyclone. Above the normal the winds move around a centre nf digit pressure in a direction against the hands of a watch. Those winds are believed to have a downward tendency, so the air is clear and dry, and, while the days are sunny, the nights are cold.

Low-pressure areas come mostly from

the tropica, hut -waves of low pH »sure called “Antarctic disturbances” some via southern Australia, and mostly affect the South Island, but make strong westerly winds further north. With regard to the prediction of weather: Aided by the barometer and thermometer, careful observers of indmtitfras in the clouds, sunsets, etc., often gain great proficiency in forecasting the weather of the locality in which they reside. In conclusion, it is the climate which makes New Zealand what it is. The soil of Australia is just as rich; but, t.V*Mgh Australians cultivate an acreage t\v«,.tyono times greater than we do, yet I / .ave seen it, stated on good authority that the'r total yield 19 only five times -greater than thqd produced by the farming population of this small colony.' Assets like our scenery and gold-mines are all valuable, but our climate is the most valuable of all. The climate of New Zealand needs further study preparatory to its more scientific expo-sit'on, so that its advantages may be definitely realised. Farmers have a direct and immediate interest in the cEmate, and leaders of thought in agricultural communities can do much to further the aims of meteorology in what may not only be of interest to everybody, but of especial benefit to the farmer.