The growth of all plants depends on a supply of water which is normally obtained through their roots from the soil. Plants use enormous quanities of water during their growing period, and although some of this water is used to carry soluble food into the roots and some is used to assist with carbohydrate production, the amounts used in these ways are small compared with the total consumption. For where a large proportion of other nutrients ~absorbed~by-the~plant-is~retained,~a~continuous_flow_ofwaterfrom~ the soil into the plant roots and out through the leaves must be maintained.
In 1955-56, 303 aircraft made I,183,794 flights from over 8000 airstrips to drop 404,933 tons of fertiliser, 4401 tons of fencing materials and rabbit poison, as well as 374,s I1 gallons of spray. In the early days of aerial farming light aircraft were successfully flown from paddocks or airstrips where little grading had been done-oua& atten&givei+to~fe*-a-hard= wearing sward. More recently with the use of newer types of aircraft lifting heavier loads, permanent airstrips have been constructed, some at considerable expense and in many cases to serve a number of neighbouring farmers. Up to 1000 tons of fertiliser may be flown off an airstrip in a year.
Lotus uliginosus, commonly called Lotus major, is an important perennial legume in our grassland economy. It has proved valuable as a pioneer legume on peat, pumice, and hill country, where its rambling growth enables it to compete favourably with rushes, scrub, or fern, and as a permanent component of the wetter hill country where it is the important legume wherever the fertility and aspect are not optimum for white clover. It withstands heavy grazing and spreads both rhizomatously and stoloniferously. However, the material available is of great variability, the species in general establishes poorly from seed, and at Palmerston North is dormant in growth throughout May to August.
The title is chosen for the sake of brevity, but I am forced to go beyond it to present a balanced picture of the subject. 1.0. Definition. It is valuable to start with a definition and the one I prefer is this: “Irrigation is the process of supplementing natural rainfall so that adequate moisture shall be always available to the growing plant.”
In the past twenty or thirty years there have been many changes in farming techniques, brought about through increased knowledge of the science and practice of agriculture. The puru paper is not so much to dogmatise on methods of pasture establishment as to throw the subject open to discussion from which all of us may benefit.
Of the three factors which indicate quality in seed-purity, germination, and strain-germination is the one most fully appreciated by those trading in or sowing seed. Before germination can take place conditions must be suitable. The conditions can best be described as being suitable when there are present the required amounts of water, warmth, and air, and, with certain seeds, light. In the laboratory suitable conditions for each species are provided and the resulting germination figures show the maximum germination possible under ideal conditions.
It is becoming increasingly evident from work carried out by various groups of research workers throughout the world (Thomas and Hill, 1949; Blackman and Wilson, 195 I ; Donald, 195 1, 1956; Black, 1955; Watson, 1956) that the amount of light energy available to herbage and crop plants is a major controlling factor in plant growth. In a recent review article Black ( 1957) has stated, “It is clear from the evidence herein reviewed that the growth of pasture species, as of other plants, is markedly dependent on the light environment, and that the quantity of light energy available rather than the intensity appears to be the important factor. Apparently the greater the quantity of light energy available up to the highest values recorded in the field, the better the growth.”
The recognition of sulphur deficiency during the last few years over large areas of the South Island may be said to have originated in trials by Lobb (1953, 1954). The implications of earlier work by Doak (1929) and others had not been fully appreciated. After seeing some of the responses obtained by Lobb in North Otago, we at Lincoln decided to examine the nature of sulphur responses in Canterbury. After some initial experiments on rape (Walker, Adams, and Orchiston, 1954), where sulphur was shown to be of slight importance, emphasis was shifted to the tussock country in the Canterbury foothills (Walker, Adams, and Orchiston, I955 and unpublished data). This paper will summarise most of our work.
Fourteen years have passed since short-rotation ryegrass, or H I (Hybrid No. I) as it was then called, was first released, and the executive committee of the Grassland Association thought that the time had arrived when a stocktaking could be made of the grass; hence this symposium.
I can speak with any authority only of spray irrigation as applied to dairy farms in the Auckland Province, with some side references to results in other parts of New Zealand and in Australia; and I want to try to show that pasture irrigation in the Auckland Province as a general rule is neither economic nor profitable; in a few special cases it is economic; and in still fewer, profitable. By “economic” I mean as an aid to efficiency; and by “profitable” I mean as disclosed by cost accountancy. Other people use the terms “economic”, “profitable”, “payable”, and “worthwhile” indiscriminately in reports from which I shall quote.
In 1858 H. S. Thompson, writing in the “Journal of the Royal Agricultural Society”, quoted an ancient Persian proverb, “The sheep has a foot of gold, and turns to gold whatever it touches”, and wrote that, although at first he agreed with the proverb, he rapidly became dissatisfied with it. In his experience-sustained heavy stocking with sheep caused pastures to deteriorate. In my opinion his impression was that the sheep’s “foot of gold” was a complex influence with benefits accruing from returned dung and urine and penalties imposed by untimely defoliation which necessarily entailed treading. He believed that it was important to use young cattle on establishing pastures “until the turf is close and strong enough to bear the treading of heavy cattle.” In 1873 he reaffirmed his opinions with an amendment that carefully managed sheep should be the first on pastures intended for cattle grazing. His opinions, in the main, agree very well with modern ideas. A local opinion has been that for vigorous growth of perennial ryegrass, plants must be continually pushed into the soil, which must be compressed around them. Accordingly, hoof cultivation has been of wide popularity; it is not uncommon to be told that a good pasture should be “blackened” once a year.
The previous paper dealt with the broad fundamentals underlying the moisture requirement of pastures. In making my contribution to this symposium I will attempt to consider the implications of these principles in determining a practical irrigation schedule and to discuss the management of irrigated pastures. Firstly the irrigation schedule: Mr Rickard has indicated that the rate of water use by pastures is between 0.1 and 0.2 per day and that growth begins to be affected when the amount lost from the soil is of the order of 1 to I in., that is, when a deficit of 1 to 14 in. is built up.
Apart from pedigree white clover no pasture species has had more impact on the College farm than short-rotation ryegrass. Equally spectacular has been the decreasing dependence on swards based on perennial ryegrass.
The farm is situated on an arm of the Tauranga Harbour, on the Omokoroa Peninsula, 12 miles north of Tauranga and is on a narrow strip of rolling country between the Kaimai Hills and the sea. The land on this peninsula consists of a ridge down the centre, with rolling lands going down to sandy swamps and flats on each side. The farm is divided into three by two shallow gullies, which drain a considerable water-shed above the farm, necessitating a lot of draining.
It is necessary when a farmer like myself is giving a paper such as this that he should first acquaint you not only with the location and type of his farm, but also with a brief history of his farming experience so as to enable you to get some perspective as to the value of what is said.
Most agriculturists are familiar with the use of selective wcedkillers for the control of weeds in crops and newly sown pasture established in conjunction with conventional methods of cultivation. For cultivation mechanical aids are used to reduce interplant competition and to prepare a seed-bed. In this paper I propose to establish the concept of using weedkillers as a method of reducing inter-plant competition in place of mechanical aids. The concept is based on using one or two specific weedkilling chemicals to kill the existing vegetation in situ. Pasture mixtures are then sown into the dead turf or crops are drilled directly into the chemically destroyed turf. The paper is based on the work of the Extension Division of the Department of Agriculture.
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