Influence of Climate and Soil Types on Nectar Secretion

New Zealand Journal of Agriculture, Volume 78, Issue 4, 15 April 1949, Page 397

Influence of Climate and Soil Types on Nectar Secretion

AN important problem which the beekeeper has to solve in the establishment of out-apiaries is not only the abundance of the nectar-producing flora in the locality but also its dependability in providing both regular and economic yields of honey. Though it is true that to a large extent a beekeeper must take whatever yield the district can furnish, it is also true that when he studies his district with an understanding of the principles which govern plant growth and nectar secretion, the honey-production potential can usually be forecast more easily and exploited more fully. In this article E. Smellie, Apiary Instructor, Department of Agriculture, Christchurch, discusses the influence of climate, soil fertility, and topography on nectar secretion in Canterbury.

FACTORS which influence nectar secretion continue to be a subject for much speculation among beekeepers, showing that the physiology of nectar secretion is not yet understood fully. Nevertheless, it is known that flowers of different species secrete nectar of different types and that the nectar of any one species may differ in character and quantity according to soil, climate, and other environmental factors influencing the growth of the plants.. Climate of Canterbury Canterbury has a very wide range of climatic conditions. The annual rainfall along the coastal areas is about 26in., gradually increasing inland to 46in. in the foothills of the Southern Alps. Over the greater part of the plainland the rainfall varies between 28in. and 38in. and the average number of rain days is about 125. In general, the rainfall is adequate and evenly distributed through the year, though -in some districts the amount borders on deficiency. All areas in Canterbury Province are subject to strong north-west winds. These are hot, drying winds, which often blow continuously for several days in summer and autumn. In the lower-rainfall areas these winds reduce the efficacy of the rainfall. Temperatures vary widely between the hottest and coldest. Summer temperatures . are very warm and the atmosphere invariably has a low humidity, and winter temperatures range from mild to cold. . Successive frosts check the growth of grass and clovers. Snow rarely falls along the coastal belt, but inland areas with an altitude of 600 ft. or more usually receive at least one fall of snow each year, and in some cases it may lie on the ground for a fortnight or more. Topography The topographical features of Canterbury are of some importance to beekeepers. The Canterbury Plains, the greatest area of flat land in New Zealand, stretch some 130 miles from Amberley in the north to as far south as Timaru, widening in the middle zone to 40 miles. The plains narrow toward either end and rise gradually to a height of nearly 1200 ft. at the foothills which form their western boundary. '

Beyond these foothills high, rugged snow country, unsuitable for beekeeping, extends to the main ranges of the Southern Alps. Northward from Amberley tussock ridges and undulating hills predominate, though areas of flat arable-farming land occur in the Waikari, Culverden, and Cheviot basins. Between Timaru and the Waitaki River, the southern boundary of the province, undulating downlands and low hills extend westward from the coast for 15 or 20 miles to the first of the higher tussock ridges. In general, this is fairly-good beekeeping territory. Another area of hill .country is formed by Banks Peninsula, which consists of an old volcanic cone that has been worn down by erosion. (. Soil Types The parent material in the composition of Canterbury soils is greywacke, a substance formed from sediments laid down in water and. subsequently hardened by earth pressure. On the steep, slopes, such as in the western ranges, the soils . are derived by weathering of the greywacke gravels, but on much of the lowland country the soils were formed from windblown deposits of greywacke that was originally eroded by glacial action and later carried along and laid down in the wide beds of the main rivers. In addition to the wind formations, water-borne or alluvial deposits also occur along portions of the main rivers and on portions of the land nearer the coast. Some of these are being added to during present-day floods. . The topsoils- ;j are dark grey to black and vary in depth, giving rise to soil variations in texture, water-holding capacity, and fertility. The parent soil-forming materials in Canterbury are. low in phosphate and lime-bearing minerals, especially in the areas near the foothills, where leaching is greatest, and applications of these minerals are essential for present farming requirements. Surveys recently undertaken in Canterbury by the Soil Survey Division of the Department of Scientific and Industrial Research have disclosed more than 40 soil types, composed of variations of sands, stones, and gravel, sandy loams, silt loams, and clay loams. However, despite these variations in soil type, Canterbury agricultural areas can be classified broadly into 4 main

soil groups based on the types of farming practised—light, medium, medium to good, and heavy cropping lands. A wide range in productivity—sometimes within relatively-short distances —is a characteristic of the groups, resulting from differences in the moisture supply available to plants. For instance, on the downs and on the flats where the soil is more than 18in. deep, plant growth is affected by lack of moisture only in very prolonged dry weather, but on the flat and terrace areas where shingle lies only 9in. or less below the surface soil, moisture is invariably insufficient to meet the full demands of the better grasses and clovers. Therefore, the ability of the soil V to retain moisture for plant growth is the main factor affecting the type of farming practised and— of greater importance to beekeepers —the types of crops and pastures . grown. Farming Practices In general, the farming economy of Canterbury is built up largely around the production of wool and fat lambs, and in conjunction with this production mixed arable farming in its truest sense is practised. - About 1/6 of the total acreage of downland and plainland is cultivated each season for growing cash and feed crops, leaving only 5/6 in permanent pasture for grazing. These pastures are usually sown down with high-fertility-demanding grasses and clovers and are ploughed in every 3 to 10 years according to type of farming and soil. This renewal of the pastures is associated with a crop-rotation programme which is necessary for the maintenance of soil fertility and for the heavy grazing of a greater population of sheep and other livestock. In some areas of light and stony land only the low-fertility-demanding grasses can exist, but in others soil fertility has been raised by sound management or by irrigation systems which enable the better type of pastures to be developed and maintained. In many instances this has been accomplished on land which a few years ago was regarded as relatively poor. Canterbury beekeepers receive about 95 per cent, of their honey yield from pasture land, so the factors which influence pasture development and maintenance are of extreme importance, as they also determine both the honeyyield potential and the hive-carrying capacity of any area.

Influence of Climate

In addition to farm management influences, climatic conditions cause variations in the nature of the honey flow from season to season. For that reason it is a good policy for beekeepers to establish their out-apiaries on as many types of land as is possible to ensure consistent over-all averages each season. Usually the first white clover bloom appears in October on the lighter or warmer soils, and the main flow from

this source develops during December and January. The time of starting and the vigour of the flow are governed by the amount of moisture in the soil and atmospheric and earth temperatures. -

Light and Medium Land

.. Light and medium to light cropping soils in some instances lie in narrow strips through a heavier soil type, though in general they are compact and cover extensive areas. These soils consist of combinations of sand and silt loams with varying amounts of gravels and stones intermingled. The depth of soil in this class of land is not more than 9in., so it varies from' droughty to moisture retentive according to the amount of rainfall. Along the coastal zone the lighter soils are subject to both inadequate rainfall and cool winds. On the stony terraces near the foothills north-west showers assist the soil to retain moisture longer.

Moisture in excess of plant requirements quickly drains away from these shallow soils into the underlying shingle, and for that reason the lighter lands respond to temperature changes much more quickly than the heavier types. Another feature of . this class of land- is that sudden changes in temperature while the clover is in bloom do not retard the rate of nectar secretion for so long. However, if the clover bloom is checked by a late frost of more than 4 degrees, especially inland at altitudes of up to 1200 ft., invariably there is no further honey yield of . any consequence that season.

Extensive clover bloom always appears first on the lighter and medium soils. The period of maximum blooming, as well as being early, is usually brief because of the very rapid parching of the pastures, but during the drying-out period a vigorous honey flow develops. The average yield is usually less in the coastal regions than along the foothills and in intermediate zones where the influence of northwest showers prolongs the effective period of bloom. Maximum secretion of nectar is promoted by soaking rains . in December followed by a moder-ately-warm period. - With colony strength built up and held at its maximum at the start of the flow, yields of more than 1001 b. per colony are possible under these conditions. With moderate temperatures, in contrast to much higher temperatures, the heat radiated by surface stones is sufficient to induce nectar secretion without burning the clovers. In most seasons the honey flow from clover on this class of land has ceased by New Year, and though the seasonal yields vary in light-soil areas, the crop rarely fails completely where ’ white clover has been grown to any extent. The subsequent floral sources, such as catsear and thistle, usually are of little value in adding to this surplus, as with the parching of the soil the amount of moisture available to the plants is not conducive to a prolonged period of nectar secretion.

Where irrigation water is regulated on to light- and medium-land pastures clover growth can be maintained, and with a much longer blooming period colony averages are better. However,

honey yields from areas under irrigation are not as great as the improved condition of the pastures would indicate, not because of any adverse influence on secretion but because of the heavier , stocking, particularly of fat lambs, that the irrigation makes possible. , - ■

Medium to Good Land

Medium to good cropping land is not as extensive in total area as the light and medium to light cropping areas, in contrast to which most of the medium to good areas are formed in long narrow strips. Most of these strips are on the south sides of the main rivers and were formed from silt that was dried and blown by strong northwest winds from the very wide riverbeds following the receding of water after each flood. The soil in consequence is mainly a silt loam, usually 18in. deep or more, overlying the shingle and sand deposits.

This class of land is very fertile

and, because it can withstand drought conditions for much longer than the lighter soils and drains more freely than the heavy alluvial soils, it is without doubt the most

reliable for honey production.

Pasture growth is very vigorous on these soils, and to use them to the best advantage paddocks are first grazed very heavily or shut up for hay, and . then left later to produce seed from the grasses and clovers. The second growth of white clover has very short stems, and the bloom is very dense toward the end of December. As soil temperatures are then also ideal for inducing nectar secretion, the main honey yield is gathered from then until the end of January or later, according to.. the season. Though a soaking rain in December is a decided advantage,' its absence is not as serious on this class of land as in the lightersoil areas. The honey yield from white clover is supplemented substantially by yields from .catsear, thistle, and, in very dry seasons, lucerne. Average seasonal yields are about lewt. or more per hive.

Heavy Land

As the heavy cropping land was formed from alluvial deposits, most of it is in coastal zones near the main rivers. Typical heavy cropping land is located in fairly-compact areas such as in the Ellesmere, Tai Tapu, Temuka, and Willowbridge districts. Other heavy-land ? areas are in very narrow strips in some inland locations alongside the larger rivers. The cropping of these areas is associated with dairying and the growing of high-producing pastures. Fat, lambs and wool are also important, and pastures are usually left down for a number of years.

; The soil is of great depth and has a clay base. Therefore it is very moisture retentive and in consequence requires a long period of hot weather to develop the soil temperatures necessary to promote a vigorous secretion of . nectar by white clover.

White clover blooms prclifically in most of the heavy-land pastures, ,but

because of poor or inadequate drainage many of the areas in bloom do x not yield a satisfactory honey crop. In other districts poor drainage . has soured the soil and prevents a suitable clover establishment. Drought conditions are ideal for a maximum honey yield from white clover, but as these do not occur with any frequency the average yield in this class of country does not exceed 901 b. per colony. In very wet seasons a crop failure is always possible, despite an abundance of clover bloom. The main honey flow from clover in these areas usually begins in January, or in late seasons in February, and clover is' in bloom until late March or April. During the past few .years. State drainage schemes have improved the productivity of some waterlogged districts, and in consequence beekeepers have received satisfactory yields in what previously was poor honey-pro-ducing country.

Analysis of Potential Yields

The medium to light and medium to good cropping soil areas are of more value to the Canterbury beekeeper than either the extremelylight or the heavy soils. In a choice between extremes, the lighter soils can sometimes give more reliable yields and averages than the extremely-heavy soils which seemingly show a better prospect.

With low humidity, absence of cloud, and a high number of days of hot sunshine favouring the secretion of nectar, Canterbury .districts are also subject to low rainfall and to cold east winds which cause a break in the flow. The strong north-west winds cause severe mortality among flying bees, and in some years this factor seriously reduces the crop average; in other seasons these hot winds partially evaporate the floral secretions and 1 leave in the nectaries a viscous residue -which the bees have difficulty in gathering. . , > The radius of bee flight during the flow is not usually very great, and that, with the acreages in . other: farm crops, makes the hive-carrying capacity of out-apiaries very , small. The vigour of the main flow, particularly on the lighter land, is another influence. In general, outyards are established | to 1 mile apart, with between 20 and 30 colonies in each, and in average years that may be considered capacity stocking. Undulating country such as is found in. the north, and south extremes has soils overlying clay formations, and these react to'temperature changes more rapidly, especially on the sunny faces, than do the alluvial clay-based areas. Undulating country, in the main, is "fairly consistent for honey production, especially when lime has been applied and good clover pastures have been established, but at their best the honey yields from it seldom compare with those .from the medium to good cropping soils overlying the shingle and . sand formations on - the plains.