THE GRAZING ANIMAL AND SWARD PRODUCTIVITY

A trial designed to show the effects of animal excreta on sward productivity is described.
It was estimated that the grazing sheep returns in a season nutrients capable of immediate uptake by the plant equivalent to 5–6 cwt. nitro-chalk and 2–21/2 cwt. 60% muriate of potash per acre.
A large part of sward yield depended on animal return. Clover depression from the effects of animal excreta and, under mowing treatment, from the effects of fertilizer nitrogen, did not result in marked loss of transferred clover nitrogen. There appeared to be a gain in clover soil-nitrogen from a reduction of the clover stand.
A comparison is made between the restilts obtained from sheep excreta on the sward with those obtained from mowing treatment.
The interaction between animal or fertilizer nitrogen and the clover plant is discussed.     

Effects of fertilizer on yield and quality of Norland potatoes in northeastern Saskatchewan

Fertilizer combinations designed to study the effects of phosphorus, potassium and sulfur on yield, early tuber yields, and quality of potatoes were tested in each of three consecutive years at two sites in northeastern Saskatchewan. Yield responses to fertilizers varied from 0 to 136 cwt/acre and averaged 73 cwt/acre. Phosphorus fertilizer requirements of potatoes were lower for the Nipawin soil type (0–35 lb P/acre) than for the Melfort soil (35–140 lb P/acre) and were related to available phosphorus levels in the soil. Fertilizer containing potassium (50 lb K/acre) consistently increased early tuber yields at both sites. Yields of potatoes harvested at maturity were significantly increased by potassium at Nipawin. At Melfort, potassium fertilizer did not increase yields when potatoes were harvested at maturity. Over-fertilization with nitrogen reduced early tuber yields at Nipawin on two occasions. All fertilizer combinations significantly reduced specific gravity of potatoes, compared to the unfertilized checks. Increasing the rates of phosphorus and adding potassium generally decreased specific gravity. These effects were, however, not significant in the three-year averages. Differences in specific gravity of up to 0.006 were not reflected in overall quality ratings for boiled or baked potatoes. The addition of sulfur from gypsum did not affect early yield, final yield, or specific gravity at either site.     

THE RESPONSE TO FERTILIZER TREATMENTS OF WINTER WHEAT GROWN AFTER LEYS

Over three years, eight replicated experiments were conducted in which winter wheat was sown after a ley with and without seedbed applications of P and K. Fertilizer N was applied at 0, 45, 90 and 135 lb per acre in one dressing in early spring. Observations were made on tiller counts, grain size and yield.
There were no significant interactions between N and mineral fertilizer. Mineral fertilizer had no important effect on tillering or grain yield. Consideration of the previous fertilization of the pastures showed that there was probably an adequate reserve of P and K in the soil, although soil analysis did not always reveal it.
Nitrogenous fertilizer significantly increased fertile tiller numbers and raised yield of grain up to an application of 45 lb N per acre in 1960 and 90 lb N per acre in 1961 (after a wet winter). The average responses to 90 lb per acre of N after leys were 74, 6·3 and 101 cwt grain per acre in 1959, 1960 and 1961, respectively. In 1961 the corresponding response in an arable field was 16·3 cwt.
It is concluded that after a well-fertilized ley neither mineral fertilizers nor N are necessary in the seed bed and that the ley contributes about 45 lb N per acre towards the succeeding crop. The practical advantages of autumn drilling without fertilizer are stressed and reference is made to the importance of considering fertilizer applications for the rotation as a whole.     

Nitrogen fertilizatioin of potatoes for early summer harvest

Rates of N applied to sandy loam soil with wheat as the preceding years crop was studied as to the influence on tuber yields of potatoes grown for early summer harvest in Southwestern Indiana. Most of the yield response was to the first 75 lbs/acre (84 kg/ha) increment of N which increased the yield of US #1 potatoes 61 cwt/acre in 1967 and 52 cwt/acre in 1968. The total solids were not significantly decreased by the first increment of N applied which was also the N range of rapid yield increase. N fertilization increased the N content of the foliage from 3.0 to 4.0% in 1967 and 3.97 to 5.17 in 1968 and the tubers from 1.36 to 2.96 in 1968. The first 75 lbs N increment was efficiently converted to crude protein, 48% incorporation, but the succeeding increments were poorly converted.     

Effect of nitrogen,phosphorus, and potassium fertilizers on yield components and specific gravity of potatoes

Netted Gem potatoes were grown at four levels of N, three of P, and two of K fertilizer in metal lysimeters protected from rain by an automatic shelter. The first two increments of N fertilizer, 200 and 400lb/acre (224 and 448 kg/ha), successively increased yields by increasing the number of tubers produced. The first increment also increased the average tuber weight. With 800 lb N/acre (896 kg N/ha), tuber yield and grade of potatoes were reduced from those of the 400-lb/acre (448-kg/ha) treatment becuase the average weight per tuber was reduced. P fertilizer increased yield by increasing the average tuber weight. The increased yield due to N and P fertilizers was almost entirely in the form of Canada No. 1 potatoes. K fertilizer did not affect number or weight of tubers in this high-K soil.     

RESPONSE OF GRASSLAND TO NITROGENOUS FERTILIZER IN THE WEST OF ENGLAND

Extensive replicated plot experiments were carried out at Henley Manor Farm from 1956–1961 to obtain accurate measurements of herbage production and response to nitrogenous fertilizers under West of England conditions. 356 plots were used; use of the herbage by both cutting and grazing was studied. The principal results are: Grass/ clover swards (containing approx. 35% clover) grown without nitrogenous fertilizer averaged 75 cwt dry matter per acre per annum. Application of nitro-chalk to initially grass/clover swards reduced the clover content of the herbage. About 133 lb N/annum was required by an all-grass sward to equal the production of a grass/clover sward without N. Attempts to increase production of grass/clover swards by using N for early growth and relying on clover for mid-season growth were unsuccessful in 2 out of 3 years. Swards (initially grass/clover) gave significant increases in total dry-matter production from regular use of the lowest level of N (26.0 or 34.7 lb N/acre/cut or graze) in 44 out of 49 cases. Extremely high yields were obtained from the heaviest use of N (104.2 lb N/acre/silage cut). 52.1 lb N/acre/cut or graze was the optimum rate of application on ail-grass and grass/clover swards. Up to about 350 lb N/acre/annum the dosage-response curve was very nearly straight for all-grass and grass/clover swards. On the grazed plots herbage left ungrazed amounted on average to only 6% of the total. The health of all stock on the high nitrogen plots (as well as all others) was excellent.     

CLOVER NITROGEN AND SWARD PRODUCTIVITY

Under mowing conditions in the absence of the animal, ultra-simple swards based either on ryegrass or cocksfoot gave large increases in yield of dry matter and nitrogen from the inclusion of white clover in the seeds mixture. Raising the clover seed rate from 1 to 3 lb./acre gave a further response in yield.
As the swards aged, the continuing effect of increased clover seed rate was dependent on applied nitrogen.
The rate of transference of nitrogen from clover to the soil depended upon the species of the associated grass, the clover seed rate, the age of the sward and the degree of reduction of the clover in the sward.
Suppression of clover led to an increase in soil nitrogen, particularly with high seed rates of clover.
Dry matter response to applied nitrogen (69 lb./acre/annum) was greater in cocksfoot than in ryegrass. Fertilizer nitrogen had little effect on the yield of nitrogen from the sward except where the high seed rate of clover had been used.     

A COMPARISON OF THE REACTION OF DIFFERENT GRASS SPECIES TO FERTILIZER NITROGEN AND TO GROWTH IN ASSOCIATION WITH WHITE CLOVER

Seven species or varieties of grass, and a mixture of 3 of them, were sown in pure swards and treated with 4 levels of nitrogenous fertilizer (0,17·5, 35 and 70lb N per acre per cut). Each species, and the mixture, was also sown with white clover. The experiment was cut 4 or 5 times per year. The effect of fertilizer on the yield of each grass was compared with the effect of clover on the yield of the grass/clover swards. Mean annual yields showed an approximately linear response to N; there was a small but significant fall in response to the highest level of N. Response among the species ranged from 20 to 30 Ib of dry matter per Ib N applied for the intermediate level of fertilizer and from 14 to 23 Ib for the final increment of fertilizer.
S37 cocksfoot, S48 timothy, S24 ryegrass, and a mixture of these grasses, were high yielding and responded well to fertilizer N; Irish ryegrass and Agrostis tenuis were less productive and gave poorer responses to N. S215 meadow fescue and S23 ryegrass were intermediate in yield and response.
There were no significant differences between the annual yields of the 8 grass/clover mixtures; the yields of the grass and clover components of each mixture were inversely related. The effect of clover on the yield of the grass/clover mixtures was estimated to be equivalent to the effect of an annual application of 205 lb N per acre to Agrostis tenuis and 120 lb N to S48 timothy. The fluctuations in annual yields were greater with grass/ clover mixtures than with grass swards receiving N.
The yields of grasses when sown with clover were in similar order to their yields when sown pure; but whereas the latter tended to fall from year to year, the yields of the grass components of mixtures (except Irish ryegrass) did not.     

THE INFLUENCE ON THE FOLLOWING ARABLE CROP OF SHEEP EXCRETA AND FERTILIZER TREATMENTS APPLIED TO A LEY

The differences in soil fertility in a ley as a result of treatments applied for four years in a sheep-grazing trial were measured by growing crops of wheat and kale. The pasture treatments had been: control, dung, urine and dung plus urine, each combined with four levels of fertilizer nitrogen.
Yields of winter wheat harvested in 1956 ranged from 27.1 to 38.6 cwt. per acre. Plots to which faeces had been allowed to return during the pasture phase outyielded (p <0.001) those from which it was withheld. Urine was relatively ineffective except in combination with nitrogen. In the absence of animal returns, nitrogenous fertilizer depressed grain and straw yields. A top-dressing of K applied to the wheat in spring as a sub-treatment had no significant effect. The percentages of N and K in the grain were unaffected by the former pasture treatments, or by the K top-dressing.
A subsidiary small-plot experiment in which the above pasture treatments had been combined with P and K, each at two levels, was cropped with marrow-stem kale. In general, N applied to the pasture increased kale yields except where dung and urine had been withheld. Neither P nor K had a significant effect, except when combined. The leaf/stem ratio of the kale was reduced by applied N and by P (both p <0.05).
The pasture/arable-crop relationship is considered.     

FURTHER OBSERVATIONS ON GRASSLAND MANAGEMENT FOR MEAT PRODUCTION

This paper deals with the second three years (April 1954 to March 1957) of a grazing-management trial in the form of a pilot farm. The whole area of 35.5 acres was run as a self-contained unit with the object of providing grazing for as long a period of the year as possible. A system of rotational grazing was used throughout with strip- and fold-grazing at certain seasons. Excess herbage was conserved as silage and hay and fed back to stock during the winter. Beef-type steers and ewes and lambs grazed the pastures, the saleable products being fat cattle, lambs and wool. Results are presented and discussed in relation to stock numbers, animal health, herbage production and botanical composition, fertilizer application and the levels of production achieved. Over-all average fertilizer dressings per acre for the three years were equivalent to 5 cwt. per acre nitro-chalk, 2 cwt. per acre superphosphate and 1 cwt. per acre muriate of potash. The outputs of utilised starch equivalent in 1954–5, 1955–6 and 1956–7 were 2970, 2850 and 2280 1b. per acre, respectively. On the basis of the six years' results it is concluded that high production can be achieved from a system where the object is an extended grazing season; that broadcast leys can be used for winter grazing and the botanical composition of the sward maintained; that self-fed silage can be a satisfactory feed for fattening cattle; that a grazing plan is a valuable guide to management; and that the pilot-farm method is of value for certain agronomic experiments.     

Continuation of cropping sequence studies on coarse textured soils in southeastern Idaho

A potato cropping rotation study was initiated on coarse textured soils in 1969 to compare annual cropping to potatoes with potato-grain rotations. At the completion of the 1975 season, those treatments annually cropped to potatoes had been planted to potatoes for seven consecutive years. After this period of time, total yields were reduced by 14% or 55 cwt/acre (6 T/ha) when compared to yields from potato-grain rotation treatments. Soil fumigation with 30 gpa (285 1/ha) of soil fumigant (Shell D-D) resulted in no beneficial effects on tuber yield or quality.     

GRASSLAND MANAGEMENT ON A PEDIGREE STOCK FARM IN AYRSHIRE

Messrs. A. W. Montgomerie and Sons of Lessnessock, Ayrshire, manage their grassland so as to encourage full development of white clover. The method is an adaptation of the system followed in New Zealand. The results are that production in terms of stock output is high, reaching a utilised starch equivalent of 23 cwt. per acre.     

Potato prices as affected by demand and yearly production

With increased potato production in the past decade, actual price for potatoes given to growers has changed little, which means that inflation-adjusted price has decreased. Since production is the result of acres harvested and yield per acre, these two parameters to price are key to understanding price fluctuation. To quantify the relation between potato price and production, acreage and yield, NASS data from 1980 to 2002 were analyzed using linear regressions. Pricing and production showed an inverse, linear relationship, which is divided into two periods. Between 1980 and 1988, the price of potatoes (US$/cwt¹) increased by $ 1.00 with a decrease in production of 15.6 million cwt, and between 1993 and 2002 with a decrease in production of 35.7 million cwt. Prices have become less responsive to changes in production. Harvested acres account for about onethird of the annual variation in prices, while yield per acre accounts for about one-half of the variability in prices. It appears that there was an increase in demand for potatoes from 1989 to 1992 that divides the two periods. There also was an increase in the percentage of the crop being used in the frozen and fry market, and a decrease in the percentage of the crop being used in the table or fresh market during this time period. This market change could explain the difference between 1980-1988 and 1993-2002 relationships.     

Effect of antitranspirants on yield of Norgold Russet potatoes under greenhouse and field conditions

Antitranspirants (AT) were applied to greenhouse, field research plots and commercial plantings of Norgold Russet potato plants. In the greenhouse AT (Folicote and Vapor Gard) reduced water uptake by plants by 20–40%. In field trials at the Texas Agricultural Experiment Station, Halfway, similar concentrations increased yield of Norgold Russet potatoes by 21–45 cwts per acre (2352–5040 kg/ha). In a commercial trial on 20 acres of potatoes, 2% Folicote applied 5 and 3 weeks prior to vine kill increased total yield by 47 cwts per acre (5264 kg/ha) and increased yield of premium grade potatoes by 100%. Gross crop value at harvest was increased $500 per acre ($1125/ha). Significantly higher soil moisture levels existed in soils of treated plots between irrigations.     

THE EFFECT OF WHITE CLOVER AND NITROGENOUS FERTILIZER ON THE PRODUCTION OF A SWARD

Three-year leys of cocksfoot/white clover and cocksfoot alone were dressed with 0, 35, 105 and 210 lb. N per acre every year to provide information on the effect of clover and N on annual production.
White clover contributed 40% of the dry-matter yield but its presence was responsible for 77% of this yield where no N was used: it was responsible for less than 8%, and contributed 5%, where 210 lb. N per acre was applied annually, lt was estimated that grass alone receiving 160 lb. N per acre would yield as much dry matter as a mixed sward receiving none.
Clover had the indirect effect of raising yield of nitrogen in the companion grass by 60 lb. per acre per year. A maximum of l06 lb. was recorded in 1958.
The response of the tnixed sward averaged 10 lb. of dry matter per lb. N. Prevailing economic circumstances will determine if this level is satisfactory in practice.
The recovery of N by grass alone varied from 54% at the lowest level of N to 80% at the highest. On mixed swards apparent recovery was negative or low: N was to a large extent only replacing the effect of clover which was suppressed by its use.
Factors influencing response and the difference between that obtained under experimental and practical conditions are discussed.
The use of N to produce out-of-season grass may give good response, but may cause a reduction in clover contribution.     

STUDIES ON THE EXTENSION OF THE GRAZING SEASON

In a small plot trial good yields of foggage of satisfactory botanical composition with cocksfoot dominant were produced from a mixed-species pasture after it had been cut for silage in spring and again in summer. Production in the following year was satisfactory. The advantages of using ordinary pastures for winter grazing, especially if this occurs only during their last winter before ploughing, are discussed. From a study of various autumn treatments it is concluded that the optimum management for foggage production in the north-east of Scotland is to close fields on or near 10 August when 3 cwt. nitro-chalk per ac. should be applied; a higher rate (6 cwt. per ac), though it increased yields and percentage crude protein immediately, and also during the subsequent summer, conferred no benefits of practical importance. Effects of K fertilizer applications were negligible. Closing as late as the beginning of September gave smaller but useful yields of a higher protein foggage and the sward was less cocksfoot-dominant. Autumn closing and fertilizer treatments did not affect foggage wastage during winter, which averaged 14 per cent of the initial organic-matter yield; the percentage of crude protein in standing foggage rose.     

Effects of antitranspirants on yield,grade distribution,and water use of potatoes

The influence of two antitranspirant materials on yield and grade distribution of potatoes was studied during 1975 and 1976. An experimental material (AmChem 74-A335)³ was tested in 1975 at 1:9 concentration in water and 150 gal. of spray per acre (1402 1/ha). Yields of >8 oz. Norgold Russet tubers were increased by 96 cwts per acre (10741 Kg/ha) with no change in total yield. The yield increase was due to an increase in tuber size, as total numbers remained unchanged. Formulation problems rendered the material unavailable for tests in 1977. In 1976 a different antitranspirant (Folicote)³ was studied at Lubbock and Hereford at 1:100 and 1:50 concentrations in 50 gal. water (1402 1/ha). Applications were made at bloom and four weeks later. The Lubbock trial included two irrigation regimes and in each trial both Red LaSoda and Norgold Russet response was studied. The antitranspirant resulted in yield increased of >8 oz. grade Norgold Russet potatoes at Lubbock with no effect on total yield. Total yield of Red LaSoda potatoes was increased by 135 cwts in plots irrigated less frequently at Lubbock with no increase in more frequently irrigated plots at Lubbock and Hereford. Antitranspirants reduced peak soil moisture tension levels by 10–15 centibars (cb) for several weeks after application indicating the potential for extending the period between irrigations.     

A STUDY OF THE INFLUENCE OF NITROGEN ON THE ROOT WEIGHT AND NODULATION OF WHITE CLOVER IN A MIXED SWARD

Experiments are described in which a study was made of the top growth, root weight, nodule number, and type of nodules of white clover growing in a grass sward in the field. Soil cores were taken and the clover root-system examined after removal of soil by washing.
The most important factor governing the total number of nodules and the number of large (2 mm. or more in length) nodules under the sward was the amount of clover root-material present.
Nitrogenous fertilisers and the return of dung and urine by grazing sheep reduced the amount of clover root-weight and consequently the number of nodules found under the pasture. 36 1b. of nitrogen applied in the early spring of 1956 had a beneficial effect on both clover top-growth and nodulation. 80–100 1b. of nitrogen per acre had no effect on the number of nodules per gram of root. However, the application of 200 1b. of nitrogen per acre caused a significant decrease in the number of large nodules per gram of root.
The numbers of large nodules present reached a midsummer peak where nitrogen was not applied.
During the autumn many nodules showed part green and part pink colouration or were completely green or brown, an indication of a decline in nitrogen-fixing ability. Decaying nodules increased considerably in number when the legume was being suppressed by nitrogen application and top growth was poor. The practical application of these results is discussed and methods of maximising the benefit from clover and fertiliser nitrogen are suggested.     

Dynamics of perennial ryegrass and white clover in sown swards in NW Greece

Seasonal dynamics of white clover and perennial ryegrass were examined in sown perennial ryegrass/white clover swards subject to a 2 × 2 factorial treatment combination of defoliation (rotational grazing by sheep and cutting) and nitrogen fertilizer application (0 and 40 kg N ha^–1 year^–1) in NW Greece. Sward surface height and percentage cover were measured before and after five defoliation periods in 1996 within permanent microplots (30 × 30 cm, divided into nine cells) in which white clover was either initially present or absent. Both white clover and perennial ryegrass achieved maximum height and cover in April–May. Defoliation treatment and whether white clover was present initially significantly affected height and cover of both species. Total plant cover was similar prior to all defoliation periods except in July, a time of drought. Cover of perennial ryegrass was greater where white clover was initially absent, but total plant cover was greater in microplots containing white clover and the extent of the differences varied during the year. In contrast, N fertilizer application had little effect on species cover, other than small reductions in white clover cover. When white clover was present in April, it was found in virtually every microplot cell until July, but if it was absent in April there was little colonization of the microplot.     

THE INFLUENCE OF VARIOUS FORMS OF NITROGENOUS FERTILIZER ON THE GROWTH OF A PERENNIAL RYEGRASS / WHITE CLOVER SWARD IN EARLY SPRING

The effect of 4 or 5 forms of nitrogenous fertilizer on the yield and botanical composition of a perennial ryegrass/white clover sward was examined in 3 different years. The uptake of N by the grass was also estimated. Ammonium nitrate (as Nitro-Chalk), ammonium sulphate and urea gave similar yield increases, although in one year, when high rainfall followed the application of fertilizer, urea was slightly inferior. Gas liquor gave variable responses in the 3 years. Nitroform, a urea-formaldehyde, was generally less effective than the other forms of fertilizer. The uptake of N from Nitro-Chalk, sulphate of ammonia and urea did not vary greatly from year to year although the uptake of soil N by the untreated control did.
Response to N in the yield of dry-matter varied from year to year. This variation was due partly to differences in the amount of clover present and partly to differences in the extent to which N taken up by the grass was used for the synthesis of dry-matter.
The white clover content of the sward was not greatly reduced in spring by the application of the fertilizer, and there were no consistent differences between the effects on clover of the forms of the fertilizer. A reduction was apparent in the summer but not in the autumn.
It may be necessary to increase replication above the level of 3 to 6 which is frequently employed in field experiments if more precise quantitative estimates of response and of the relative efficiency of various forms of nitrogenous fertilizer are required.