GRASSLAND PRODUCTION in NEW ZEALAND

New Zealand Journal of Agriculture, Volume 64, Issue 2, 16 February 1942, Page 103

GRASSLAND PRODUCTION in NEW ZEALAND

Measurements of the amount of feed produced during the year by pastures in various districts throughout New Zealand and in several varying seasons have a direct application to farm practice and management. The following preliminary survey indicates the results

which may be expected from this type of work, and the methods by which it is carried out. It should be noted, however, that the full value of this investigation can be secured only by a continuation of measurements over a large number of years.

Measuring the Amount of Feed Produced by Pastures

By

A. G. ELLIOTT,

Crop Experimentalist, and

P. B. LYNCH,

Assistant Crop

Experimentalist, Fields Division.

Ty’Oß many years there has been a FOR many years there has been a need for a more detailed knowledge of the production from pastures throughout the year, and for information concerning the species contributing to that production. This was particularly noticeable when the. investigations concerning facial eczema began, for the rate of pasture growth at certain critical periods is in some way connected with the incidence of that disease. Consequently, in the years following the major outbreak in 1934-35, the development of a satisfactory technique was in progress, and when a useful method was discovered, several “rate of growth” trials were started.

Technique of Measurement

Pasture growth is probably the most difficult crop to measure under conditions approximating those of normal farm management. Unlike the wheat crop, for example, where measurement is restricted to one crop, pastures may be considered as a number of crops growing in association. Each pasture species has different times, rates, and habits of growth, and all are delicately balanced in the sward. The sward is extremely sensitive to changes in management, and as frequent cutting necessitates .a z drastic change, the mower has to be used with the great-est-care. The kind and severity .of stocking will also greatly influence the type of pasture and its production, and therefore the grazing management of the trials is important.

The methods employed in measuring pasture growth may be summarised as follows:

(1) “Mowing and Grazing” Trials

These were developed by Mr. A. W. Hudson,* a former Crop Experimentalist to the Department, and the technique used involves the use of a pair of similar fields, the growth in one of which is mown' and weighed, while that in the other is grazed. Mow-

ings alternate with sheep grazings, so that after two mowings and weighings the sward is grazed and the production of the duplicate section is measured. This technique approximates that of intensive rotational graz-

ing with sheep, and usually gives very high pasture production and stocking figures, indicating that it is a highly satisfactory method of management. Unfortunately, however, very few farmers could hope to maintain the sward in the condition in which it is kept in these trials, and therefore the technique is somewhat unsatisfactory as a means of studying pasture production under normal farm management. This is no reflection, however, on the usefulness, of the method for comparing various pasture treatments.

(2) “Mowing Only” Trials

Under continued mowing without the return of clippings or the use of stock, the sward deteriorates rapidly with the ingress of weeds and the lowering of production. Returning the mower clippings, which usually quickly dis- , appear from the top of'the grass, will . considerably prolong the period before the sward starts to deteriorate. However, in no way does this method approximate “normal farm management,”

and for this reason it cannot be considered satisfactory. ■

(3) “Enclosure Method”

. Essentially, this method consists of erecting movable “frames” or “enclosures” (which are 11 ft. square or lift, by 5 ft. 6 in.) in a : paddock under good average grazing management, typical of the district- and type of farming. The production of the area enclosed by the frame is measured by mowing, and then the 1 frame is shifted

to a new site. This method involves the least change from standard farm management, and has proved very satisfactory both with sheep and dairy cattle grazing.

Frames are erected in pairs (in numbers sufficient to give ’ accurate measurement) and from each pair one weight is obtained in the .following manner. Let us suppose . the frames are A and B: —

Jan. 10. —Frame A is placed in the paddock.

Jan. 17. —The herbage in frame A is trimmed to an even height with the mower. Frame B is “placed.”

Jan. 24.—The herbage in Frame A is mown and weighed (giving production in the week Jan. 17-24), and the frame is shifted to a new site. The herbage in Frame B is trimmed.

Jan. 31. —The herbage in Frame B is mown and weighed and the frame is shifted. The herbage in Frame Ais trimmed. / . ' ’

Such a technique enables continuous production records to be secured, and is applicable in practically any reasonably controlled field. In addition, it in no way interferes with the normal grazing of the field.

It will be noted that 'the • technique allows the herbage >to recover after grazing, and then to be trimmed to an even height, before leaving for mowing and weighing. Both the recovery period and the trimming are. deemed necessary to remedy the uneven height of pasture left after grazing, the recovery period ensuring that those areas grazed shorter than “mowing height” will recover to that height before production measurements are started. To some extent, this trimming technique interferes with the normal recovery after grazing, but it is essential for accurate records, and appears to exert a comparatively small effect.'*' J

With the rate of growth trials, cutting is made at regular intervals (usually about seven- days). At certain periods there may be no growth . to cut, at such an interval, and in that case the fact is recorded, and the frames are left in position. Such a technique enables the fluctuations in growth rate to be more 1 accurately

measured than one in which cutting is made at a comparable stage of growth in each case. The latter method is commonly employed where the effect of various pasture treatments is measured. When the production data is examined in comparison with the known carrying capacity of the area, a satisfactory ' correlation has been found using standard English digestibility data and maintenance and production requirements for various classes of stock. This relation has been determined for different periods of the year. Allowance has always to be made for the incomplete utilisation of feed by stock.

Results from Rate of Growth Trials.

(1) Changes in Seasonal Growth Rate

In the “Journal” for June, 1941 (page 42) the authors have summarised the variations in seasonal production of a “mowing and grazing trial” over an eight-year period. Graph 1 in the present article deals with a rate of growth trial at Karamu (Waikato) which has been in progress for the past three years. In graphs 1A and 2 the total production in pounds per acre per day is indicated by the top line and the production of each species which go to make up this total production fill the space between this top line and the base line. Thus, in Graph 1A for October 1, 1938, the sward was yielding 32 lb. dry matter per acre per day. This 32 lb. was made up of 18 lb. ryegrass, 4 lb. cocksfoot, 2 lb. white clover, and 8 lb. other species. Unfortunately, the type of pasture in the field on which the trial was started was a leniently grazed rye-grass-cocksfoot-white clover sward.

After the first year,,, the frames were shifted to a field carrying a dominantly ryegrass-white clover sward under reasonable sheep grazing. The graph illustrates this change in species composition, and the total production for the first year is therefore not strictly comparable with that of the remaining trial period. Nevertheless, the two most recent seasons have been highly productive in comparison with ’ 1938-39, which was marked by a severe autumn drought. This is reflected in the production in each season, shown in section B of the graph and also in the following table.

In the article referred to above, five features of pasture growth were given, namely: (1) The variation in seasonal production within each year.

(2) The variation in total production from year to year. (3) The unreliability of the autumn flush of growth. (4) A tendency for a summer slump in pasture production. (5) The relative constancy of spring and winter production respectively. With the possible exception that there is a greater tendency for variation in spring production in the Waikato, the rate of growth trial at Karamu confirms the above conclusions. The necessity for the conservation of surplus spring and summer pro-

duction is shown by the fact that more than 70 per cent, of the total yearly production has, on the average, occurred during the months October to March inclusive. A similar state of

affairs exists in the majority of districts throughout New Zealand. The effect of various meteorological factors on 7 pasture growth has been closely studied, but the prediction of grass production by such means has proved difficult. In the Waikato, a critical level for temperature is about 50 degrees F. for the 4 in; soil temperature, which corresponds to a

screen maximum temperature of between 55 degrees F. and 60 degrees F. This level needs to be attained before the marked spring rise in production occurs. Earlier work showed that in periods where rainfall is adequate, quite a close correlation exists between temperature and grass production. Thus, a 4 in. soil temperature of 55

degrees F. at Ruakura might be expected to result in a production of about 20 lb. of dry matter of pasture herbage per day from a first-class sward, and a temperature of 60 degrees F. should give between 35 and 40 lb. of dry matter. The critical level of soil moisture has proved more difficult to determine, but it was found that moisture shortage was commonly associated with soil temperatures exceeding 65 degrees F., due to the rapid loss of moisture which occurs at such temperatures.

(2) Growth of Pasture in Different Districts

Graph 2 illustrates the differences in total and. seasonal production in five localities in New Zealand. These trials may be considered to indicate typical production of the Waikato district, of the Stratford dairying district of Taranaki, of the Rangitikei plains at Marton, of average land in mid-Canter-bury, and of good average Southland country as found at Winton. The season 1940-41, in which the comparisons have been made, was one of high production in the Waikato and Marton districts, and of average production in the other districts. In each case' the

swards were rather better than the average for the district, and the manuring was according to standard practice. > , • (a) Variation in Total Production. , In pounds of dry matter per acre for the period Oct. 1, 1940, to Oct. 1, 1941, the trial in the Waikato yielded 11,787 lb., that at Stratford 4.734 lb., at Marton, 11,071 lb., at Ashburton, 2,623 lb., and at Winton 6,269 lb. . Mr. G. A. Blake, in the “Journal” for December, 1941, has analysed data from the Stratford rate-of-growth trial in relation to carrying capacity, and as a means of calculating the amount of hay and silage required for the periods of low production. He places the dry matter requirement of a cow producing 1 lb. of butterfat per day at 7,300 lb. per year. On this basis, the soil type in the Waikato (Horotiu sandy loam), on which the trial is located, should easily carry one dairy cow per acre, but in section 1 above it was shown that in a low production year only 6,300 lb. of dry matter were produced from this experiment. It is this latter figure which prevents even higher stocking figures than at present exist. With adequate conservation of hay and

/silage in the years of plenty, such as 1940-41, a carrying capacity of a dairy cow per acre on such land should be quite possible from the feed production point of view. Similarly, at Stratford it should be possible to carry one dairy cow to every 1| acres. Although in the latter case additional data on ■ the herbage . production over several seasons is needed to confirm this, carry - • ing • capacities of this order have ' been attained by progressive farmers in the ' district. The requirements of sheep for maintenance and production are still the subject of controversy. At Marton it has been found that dry sheep in a thriving condition will consume up to 3 lb. dry matter of pasture herbage per day. English data* suggests that a milking ewe will consume up to 6 lb. of dry matter per day. This is probably too high a figure. ’ As the ewe makes her greatest demands in periods of high pasture production, smaller quantities of supplementary fodder usually need to be conserved than on the dairy farm. On the balance, it appears that to carry a ewe ' and fatten a lamb on

grass about 1,500 lb. of dry matter per acre per year will be required. On this basis, it should be possible to carry six to seven ewes per acre at Marton, and this, in fact, approximates the carrying capacity of the Marton Experimental Farm, although it is higher than the average for the district. ; Similarly, at Winton a carrying capacity of four ewes per acre might be expected. Here, however, much greater provision has to be made during the long winter of negligible pasture growth, and considerable areas, have to be devoted to the growing of supplementary crops. In Mid-Canterbury (Ashburton district) li ewes per acre can be carried with the use of supplementary crops, but with irrigation, the year’s pasture production on this area was raised to 3,8751 b. of dry matter, equivalent to approximately 2| ewes per acre. Corresponding figures for the previous year at Ashburton were 1,0601 b. of dry matter (less than one ewe per acre) on the non-irrigated area, and 4,9001 b. of dry matter (more than three ewes per acre) on the irrigated section. This shows the unreliability of pastures in this district without irrigation. (b) Variations in Seasonal Production in Each District: Reference to Graph 2 will illustrate the following features of pasture growth in each district. (1) . Waikato.—-This has been considered in Section "1 above. Seasonal growth is subject to most marked variation in this district. \ ’ ;' .\ ''*• .7 ■' * ' \ ' (2) Marton. — most respects this district • shows similar fluctuations in seasonal growth to that of the Waikato, but there is probably a greater tendency for low production during dry summer and autumn weather. (3) Stratford. ln this high rainfall district, production is relatively stable from spring to autumn, although insufficient data is available to be certain of this in all seasons. The greatest variation is to be found in the length and severity of the winter period, as temperature rather than rainfall is the limiting factor in this district, much of which is at an elevation of 800 ft; or higher above sea level. (4) Ashburton. Grass production on non-irrigated land is practically at a standstill' of three or four months during the summer and autumn, and it is also negligible during the winter. As a result, the. yearly production is low, and practically all the grass is pro-

duced in the spring months. The figures show that 60 per cent, in 193940 and 56 per cent, in 1940-41 of the total production took place -in the months October, November, and December. As a result, the growing of supplementary crops is essential. Irrigation not only increases the total production, but also greatly improves 7 the “spread” of production.

(5) Winton.— Both in respect of climate and of total grass production, this district is similar to Stratford. In proportion, however, as th® following table shows, the spring production tends to be higher and the summer and winter production lower at Winton than at Stratford. This results in a long period of insufficient pasture growth, and the need for the supplementary crops is apparent.

The value of the foregoing analysis would be much enhanced if the comparisons could be extended over a number of seasons, but, nevertheless, it has shown'many weaknesses of pasture production in relation to stock requirements. No district can be considered safe in this respect. In addition, it has shown that the means by which carrying capacity can be increased and the stock adequately fed at all times of the year is to be found in utilising the peaks of production to fill the troughs. Particularly in the South Island, however, the lengthy periods of low production make it necessary to grow supplementary fodder crops in addition.

(3) Growth Period of Pasture Species

A typical pasture sward consists of a large, number of different species of grasses, clovers, and weeds. The study of the production from each of these species, and the times they make such production, is of the greatest , importance, not only in securing the maximum total production and “spread” of production, but also in keeping a proper balance between the species in order that they may make the most nutritious and safe stock feed. Graphs 1 and 2 indicate the production of the

main pasture species in various districts, and Graph 3 shows the changes in the percentages of these ' species ■ in the mown herbage based on dry weight. " . -, ... ' ,■ .... (a) Perennial Ryegrass.— is - the most' important pasture .constituent in all of the trials and in all of the districts, studied,' and it. is obvious, that the bulk of the total production comes from ryegrass. Even where the sward contains a high proportion of other species, such as at Stratford, the production from such species is relatively small compared with that from perennial ryegrass. It is . one of the . first species to produce heavily in the spring, but production is relatively lower during the summer months, when it tends to go to seed and when clover growth is strong. The percentage of the species in the mown herbage, however, keeps fairly constant throughout the .year. ■The marked rise in the. percentage of perennial ryegrass in the herbage as shown' by Graph 3D at,.the end of April, 1939, may be traced to'> the renewed vigour of this species with the first rains, after the severe drought period in the summer and autumn of 1938-39. (b) Cocksfoot. The rate of growth trial in the Waikato was on a ryegrass-

cocksfoot-white clover sward during 1938-39. Graph 1 shows that the production of cocksfoot was fairly constant ' throughout the year, : and the species made a substantial contribu tion to winter production, although' the best growth occurred in the summer. Graph 3 shows that the percentage of this species in the mown herbage tends to increase in the winter months. The trial used for Section E of this graph is one in which swards of various types have been established, and are being managed in the most suitable manner for each of the dominant species concerned. (c) Yorkshire — ln the swards which we are considering this is a weed species, but nevertheless it is such a widespread plant that its contribution to pasture production cannot be ignored. The production from the species is relatively constant throughout the year, but it is the earliest grass to “come away” in the spring, as is shown by the percentage present in the herbage. (Graph 3.) In some cases this may be a valuable feature, but, plant for plant, its production is much inferior to that of the better pasture species of ryegrass and cocksfoot, and therefore it should be, encouraged only where these superior grasses will not thrive.

(d) White Clover. — flush of white clover growth occurs from late spring through to the autumn. This is clearly seen in the graphs both of production and of the percentage of the species in the mown herbage. Early spring , and winter growth tends to be cloverdeficient, and late spring and summer growth may in some cases contain too much clover for its safe use , as a stock feed. Consequently, lenient winter, management to obtain grass dominance may be advisable in dairying districts where, cows are liable to “bloat.” In most districts, however, the aim is to increase the clover in the pasture, not only because it is an essential element in a balanced sward, but also because it is a most highly .nutritious plant, which is unsuitable to stock only when fed in an unbalanced ration. < (e) Subterranean Clover.—lnformation concerning this species is available from one trial at Ruakura during the season 1938-39 only. (Graph 38.) In this' pasture, which contained a considerable amount of the species, subterranean clover yielded more than

white clover during the early spring months and until November, / when white clover was rapidly , attaining maximum production. • There was a negligible amount of subterranean clover after flowering in ' December until the autumn seedlings appeared in February. Due to the very, dry season, however, the : : autumn reestablishment was poor. It has been, shown by this ■ trial that subterranean clover growth replaces that of white clover when the latter is comparatively dormant, and therefore the period of good clover growth'in the sward is considerably extended by its use. The difficulty, however, is to get the l two species in the ’ one sward, < because a strong white clover growth will usually prevent effective re-establishment of subterranean - clover in the autumn. (f) Other 'Species.— This article does not allow of an .investigation into the minor elements of the sward, but these vary greatly ,in amounts and times of production throughout the year.

Conclusions

In this article only a small part of the information which’ may be obtained from the data concerning the rate-of-growth trial' has been presented, but no doubt it will have -been sufficient to . show the value, scope, and practical application to which the information may be applied. Both the field technique and the method of presentation of the data is original work in New Zealand. ■ It has proved to be not only practical , in the field under a wide range of farming and climatic conditions, but also gives accurate results of great. value in grassland research. For a complete survey- of grassland production in New Zealand many more trials ' are required, and each should be’ conducted for a minimum period of five years. The value , of

such a survey should be obvious from the material now presented, and should be of considerable assistance not only to research workers and field officers, but also to all engaged in grassland farming in the Dominion.

Acknowledgments

This investigation has • been a truly co-operative effort, in which a number of officers of other Departments have been intimately associated. Of these, the dissection < of the mown ' herbage into species components carried out by the Grasslands Division, Department of Scientific and Industrial Research, has provided fundamental data. The chemists of the Animal Research Division at Ruakura, of the Plant Chemistry Laboratory, Palmerston North, and of the Fields Division, Wellington, supplied . dry matter figures from herbage samples. The meteorological data was furnished by officers at Ruakura and Wellington, and by Mr. K. M. Dalrymple, Bulls./,' The officers of the Public Works Department assisted with the irrigation trial near Ashburton. Finally, much of the value of the results secured has been due to the careful’and painstaking field work of instructors of the Fields Division and officers , of the Animal Research Division.

♦Hudson, A. W. : Imperial Bureau of Plant Genetics, Herbage Plants, Bulletin 11, 1933, 21-35.

*British Min. of Agric. : Bulletin 48 : Rations for Livestock (1933).

.Season. . . Total ■ ■ Y early Production. Production in Two-monthly intervals as a percentage of the - . Total Production. - Oct.-Nov. Dec.-Jan. Feb.-Mar. Apl.-May June-July Aug.-Sept. ■ ' - . ' Apl.-May June-July Aug.-Sept. 1938/39 6,316 - 33.6 28.0 14.0 7.2 6.9 10.4 1939/40 9,037 19.9 30.u 21.3 , 12.9 4.3 11.7 1940/41 11,787 27.7 16.5 21.8 14.9 7.5 11.7

PRODUCTION OF HERBAGE IN POUNDS OF DRY MATTER PER ACRE.

Total Yearly Production: in Twomonthly Total Periods as a Production. Percentage of 1 the District. Total Yearly Production 1940/41. Production in Two-monthly Periods as a Percentage of the Total Production. Oct.-Nov. Dec.-Jan. Feb.-Mar. | Apl.-May Apl.-May June-July Aug.-Sept. 1 June-July Aug.-Sept. Stratford .. . 4,734 22.6 ■ 28.8 24.6 1 -- ’ | 8.8 2.2 13.1 Winton 6,269 34.1 21.2 11.5 | 7.5 nil 25.7 ,

GRASS PRODUCTION IN POUNDS OF DRY MATTER PER ACRE.