Field-average based recommendations have been a common practice for nitrogen (N) rate recommendations. The problem is that, even when the same amount of N fertilizer is applied at the recommended rate, yields differ from year to year, the result being poor use efficiency. Reduced fertilizer use efficiency can result in unnecessary costs to producers, especially with a likely price of US$ 1·10 per kilogram of N fertilizer anticipated within the next few years, largely due to rising oil and natural gas prices. It has been estimated that by the year 2025 the consumption of N fertilizer will increase by 60–90%, with two-thirds of this being applied in the developing world. In light of this, methods that increase N use efficiency and profitability of farms, while reducing environmental impact, are no longer simply commendable but required in developing countries. The present review assesses the temporal variability in winter wheat with respect to N nutrition and presents improved methods, including the calibration stamp (CS), N-rich strips (NRS) and ramped calibration strips (RCS) to overcome this variability. These methods can be used either as visual tools or along with NDVI handheld sensors for accuracy. Unlike the CS and NRS, the RCS method is designed to include more pre-plant N rates in strips to improve top-dress N estimation. Hypotheses as backgrounds to these methods have been developed and tested in the USA and Mexico. However, the simplicity of these technologies suggests that many farmers in both developed and developing countries can readily apply them.

is generally used to describe the lactation curve in cattle, where yn (kg) is the average daily milk yield in the nth week of lactation (n = 1, 2, 3, …, N), a is a scale parameter, and b and c are shape parameters. The model was first proposed by Wood (1967) and is widely used in practice to describe the lactation curve for fat, protein, lactose and wholemilk production; it has also been used as a basis of a mathematical model for poultry egg production (McNally, 1971). Having estimated a, b and c by regression analysis, the total lactation yield Y (kg) can then be calculated as

Between 1953 and 1955 a series of field experiments have been carried out in Great Britain to assess the effect of sowing date on the extent and the rate of emergence of a number of varieties of maize.

The range of sowing dates was from late March till May. Records were kept of the soil temperatures, these will be reported later, and in certain experiments the water content of the soil was maintained at field capacity. In all experiments a northern flint variety and a southern dent variety were sown, in the first year only flint × dent hybrids were also grown.

There was an increase in final emergence with the later sowing dates. The northern flint varieties were superior to the southern dent varieties, while the flint × dent hybrids occupied an intermediate position. The lower final emergence of the southern dent variety was most marked at the earlier sowing dates.

Differences between varieties in the speed of emergence, taken as the number of days from sowing until half of the surviving seedlings had emerged, was observed at several centres. The open-pollinated varieties usually emerged more slowly than the flint × dent hybrids. There was a very marked difference between early- and late-sowing dates in speed of emergence.

It was possible in the second year to compare seed of high quality with that of low quality as determined by the ‘cold test’ of germination capacity. The lowquality seed gave greatly reduced final emergence, the experiments stressing the need for the adoption of a standard ‘cold test’ for maize seed, especially of that intended for sowing in north-western Europe.

The high final emergence of the northern flint varieties suggest that a gene source for resistance to soil pathogen attack is readily available. The possibilities in north-western Europe for expansion of growing grain maize would be greatly strengthened by development of varieties capable of growth at low temperatures. The experiments suggest that until such varieties are available little advantage in time of emergence will be gained by sowing maize before late April in Britain.

Carcass measurements were made on 24 Rambouillet lambs of different live weights but of the same age, and the lambs divided into 3 groups of 8 according to live weight. Group I, with the lowest mean live weight, had the lowest dressing percentage, relatively heaviest head and feet and lightest pelt, while group III, with the highest mean live weight, had the highest dressing percentage, the relatively lightest head and feet and the heaviest pelt of the three groups.

Group I contained the lowest percentage, and group II, of medium live weight, the highest percentage of muscle, while the relative weights of bone and fat tissue were similar. Group III contained the highest percentage of fat tissue and the lowest percentage of bone. The differences in the relative weights of the edible internal organs between the three groups were not significant.

Testis weight was relatively much greater in Group III than in the lighter animals. While dressing-out percentage increased with body weight, the increase was not equally distributed between fore and hindquarters. Hindquarters were relatively larger in group II than in group I; but the forequarters accounted for the greater part of the differences between groups II and III.

The inoculation with Azospirillum brasilense has the potential to reduce the use of mineral fertilizers with efficient capacity to promote plant growth and yield. Most studies on the Azospirillum–plant association have been conducted on cereals and annual grasses. More studies are needed in perennial pastures, such as bermudagrass (Cynodon dactylon (L.) Pers.) that require substantial nitrogen (N) fertilization to maximize their production potential. Therefore, pastures based on Tifton 85 bermudagrass in association with annual ryegrass (Lolium multiflorum Lam.), which were inoculated with A. brasilense and fertilized with increasing amounts of N fertilizer and grazed by lactating Holstein cows were evaluated. Three grazing systems were evaluated: (i) Tifton 85, inoculated + 180 kg N/ha per year; (ii) Tifton 85 + 230 kg N/ha per year; and (iii) Tifton 85 + 280 kg N/ha per year. Forage samples were collected before and after grazing to evaluate the responses of the plants and animals. The forage yields of the systems were 21.0, 20.8 and 22.1 t DM/ha per year and the stocking rates were 3.9, 3.8 and 4.0 animal unit/ha per day, respectively. Crude protein, total digestible nutrients and neutral detergent fibre concentrations were 162, 560 and 667 g/kg, respectively. Inoculation in pastures planted with Tifton 85 bermudagrass in combination with ryegrass (plus 180 kg N/ha per year) had a positive effect, providing forage yield and nutritional value equivalent to those with fertilization with 230 kg N/ha per year.

Two indigenous breeds of sheep in Nigeria, the Yankasa and Uda and crosses of these with exotic breeds, were evaluated for lamb weights at birth, 3 months and 6 months of age and for adult ewe weight. The cross-bred lambs were significantly (P < 0·05) heavier than the indigenous breeds at all ages. Differences among the indigenous breeds were not significant. Mature ewe weight was 40·8 kg in the cross-bred and 36·0 and 31·1 kg in the Uda and Yankasa respectively, differences between all breeds being significant (P <0·05). Lamb productivity (lamb weight per kg of ewe metabolic body weight) estimates demonstrated that the differences between breeds were small.

Least-squares estimates of effects of environmental factors on lamb performance showed that type of birth and age of dam were important for lamb weights at the three ages. Season and sex also had significant effects on birth and 6-month weights respectively. Correction factors for lamb weights were derived from least-squares estimates.

The correlation coefficient between birth and 3-month weight was significant in all breeds and ranged from 0·39 to 0·55. Three-month and 6-month weights were highly correlated with estimates of correlation coefficients ranging from 0·71 to 0·74. Repeatability estimates of birth, 3·month, 6·month and ewe weights, all as traits of the ewe in the Yankasa, were 0·25, 0·21, 0·09 and 0·48, respectively.

Non-breeding groups, I, II and III, each with six high-potassium (HK) and six lowpotassium(LK) Chokla ewes were given water once in 24, 48 and 72 h respectively. In the next summer, seven ewes (4 HK and 3 LK) from each group I, II and III were switched over to a watering schedule of once in 24, 72 and 96 h respectively and were naturally bred. All the animals were maintained on grazing alone.

Water deprivation for 72 h caused 18·8 and 19·2% body weight loss in HK and LKewes respectively; an overall average maintenance of weight loss in LK ewes was significantly higher than in HK ewes from the same group. There were significant differences in water intake due to treatments only. The HK and LK ewes from groups I and III showed a similar trend.

Pregnant ewes of HK and LK types given water once in 96 h lost 21·7 and 23·8% of their body weights respectively. Corresponding weight loss in aborted ewes were 23·8 and 33·3%. Two ewes, each from 3 LK and 4 HK animals aborted owing to water deprivation for 96 h. The water intake reached 30 and 36·5% of body weight in LK and HK pregnant ewes given water intermittently.

The wool attributes of non-pregnant ewes did not indicate a significant influence of blood potassium types. Four out of five ewes of the LK phenotype died during 3 years, irrespective of watering schedule.

The paper reports a study of the chemical composition of 25400 grass silages produced in England and Wales, of which 1040 were from the period 1961–63, 17900 (15480 clamped and 2420 baled) were from 1982–88 and 6460 (5640 clamped and 820 baled) were from 1992–93. A sample of each silage had been analysed for dry matter (DM), pH, crude protein (CP) and volatile N and in most cases for ash.

The baled silages were drier on average than the clamped silages, with a wider spread of DM contents. The clamped silages with the lowest pH on average were those with a DM content of c. 240 g/kg; clamped silages wetter than this were progressively higher in pH with reduction in DM content; clamped and baled silages drier than 240 g/kg were progressively higher in pH with increase in DM content, up to pH 5·9 in baled silages of 580 g DM/kg. At a given DM content pH was on average 0·6 units higher in baled than in clamped silages. The ash content of baled silages was similar to that of clamped silages. There was an increase in the mean CP content of clamped silages between 1961–63 and 1992–93 and a reduction in the proportion of CP which was volatile. The relationship between DM and volatile N as a proportion of total N was a curve rather than a straight line, with the steepest part of the curve at the lower end of the DM range. The wet silages harvested in 1961–63 were particularly high in volatile N. At a given DM content in the range 170–320 g/kg, volatile N was rather higher in baled than in clamped silages in both 1982–88 and 1992–93. Clamped silages with a DM content of at least 250 g/kg and baled silages with a DM content of at least 310 g/kg were typically well preserved in the sense of having <100 g volatile N/kg total N.

Effects of mepiquat chloride on gradients of shoot growth within spring barley plants (cv. Koru) were determined in two small-scale field experiments. Mepiquat chloride was applied at either the lemma primordium stage or the late carpel primordium stage of spike development in the main shoot. The shoot dry weight, stem length, spike length, number and size of florets and floret developmental score were measured for all shoots, over the period from the lemma primordium stage of main shoot spike development to the late milk stage of grain development.

Lemma primordium mepiquat chloride increased the size and developmental score of later-formed shorter shoots pre-anthesis while delaying the spike development of the main shoot and other longer shoots by up to 4 days. The overall effect was to produce plants with a reduced range of shoot and spike sizes from the end of floret initiation in the main shoot until maturity. In addition, there was a slight increase in the number of shoots per plant in both experiments. Gradients of carpel development and carpel width along the spike were reduced in all treated spikes by the time of floret abortion in the main shoot but the effects were more noticeable in shorter shoots. The number of florets initiated per plant was increased by 21–22%. All shoots contributed to the larger number of florets but again the major additions came from the shorter shoots. The few extra florets initiated in longer shoots were lost during abortion of distal florets while the 2–5 extra florets on shorter shoots were retained to give extra grains at maturity.

Application of mepiquat chloride at the late carpel primordium stage had little effect on gradients of spike size or on number, size and development of florets.

Low quality roughages are a major feed resource for ruminants in Australia and many other parts of the world. Factors limiting the intake of these roughages include their high cell wall component and low crude protein content. Palatability may also be important. Low quality roughages are frequently dusty. Hence, the present experiment was initiated to determine whether water would affect the intake of paspalum hay (Paspalum dilatatum).

A new tillage procedure was examined for the improvement in physical environment it might provide during the establishment of a vegetable crop, particularly in a dry spring. This procedure, of cultivating the soil mainly in autumn, was compared with the conventional method of cultivating in the spring on a sandy loam soil. The physical condition of seed beds prepared by the two methods was assessed by in situ measurements of soil temperature, water retention characteristics, hydraulic conductivity and surface roughness. Plant responses were compared by monitoring the emergence of onion seeds. Dry spring conditions were simulated by sheltering some plots from rain.

Final emergence, emergence time and rate of emergence were all superior following autumn cultivation for both dry and wet seed beds. The major factor affecting emergence was the coarseness of the seed bed which influenced the mechanical impedance to shoot growth. Differences in soil temperature between treatments were small, as were hydraulic conductivities under dry conditions. Preparing a seed bed in autumn rather than spring resulted in a good tilth with lower mechanical strength. This minimized the constraints on emergence when soil strength increased under dry conditions.

Physiological problems in some Fife dairy herds were thought to be associated with mineral imbalance in grass cut for silage. Consequently trials at two sites were conducted to study the effects of three levels of nitrogen and phosphorus and two levels of potassium on yield and composition of pasture cut for silage.

Nitrogen increased yield of herbage and reduced its clover content whereas phosphorus and potassium had little effect on yield or clover content. Herbage clover content and calcium concentration declined over the period of the experiment. Mean concentrations of calcium, magnesium and phosphorus were 5·8, 1·7 and 3·4 g/kg respectively. Concentrations of these minerals varied more with time of cutting and with season than with level of applied phosphorus and potassium.

Nitrogen tended to reduce calcium concentration in mixed herbage and to increase magnesium concentration in the grass component; it did not affect herbage phosphorus concentrations, but narrowed the calcium-phosphorus ratio in the second cuts. Applied phosphorus increased herbage phosphorus concentration only at the site with the lower soil phosphorus status. Potassium tended to reduce magnesium concentration in clover and, at one site, in mixed herbage; it also tended to reduce herbage phosphorus concentrations in second cuts.

Mineral uptake was increased by applied nitrogen. Mean annual uptake of calcium magnesium and phosphorus was 34, 10 and 20 kg/ha respectively.

The effects of treatments on concentration and balance of these minerals are discussed in relation to ruminant requirements and maintenance of suitable levels of the minerals in the soil.

It is concluded that normal applications of NPK fertilizer are not detrimental to satisfactory mineral balance in pasture.

Evans & Roberts (1979) considered that loworder polynomials such as mean, linear and quadratic were adequate to describe the trends that occur in treatment contrasts in long-term agricultural experiments. This conclusion was based on experience with experiments on levels of fertilizers and rates of stocking on similar pastures. In such experiments, the marked seasonal pattern in the data disappears when comparisons between treatments are followed. However, further experience with experiments comparing cultivars has shown that some comparisons still show a seasonal pattern. Such patterns may be accounted for by periodic regression (Bliss, 1970).

The use of a bone biopsy technique for skeletal studies with sheep is described. Histological examination of samples of pelvic bone removed at about mid-lactation from Scottish Blackface ewes grazing on two hill farms revealed little or no evidence of skeletal resorption. This was in agreement with the results of in vivo radiography carried out in this and another field experiment reported as part V of this series (Benzie, Cresswell, Duckworth, Hill and Boyne, 1961).

The gross energy of forages can be classified into three fractions, namely the unavailable fraction, the digestible energy fraction and the potentially digestible energy (PDE) fraction. The PDE fraction can only be made available by appropriate treatment and supplementation (Pigden & Heaney, 1969). In young forages the PDE fraction is relatively insignificant, but as the plant matures, the PDE fraction increases very rapidly. By treating matured forages with delignifying agents, increased nutrient digestibilities have been demonstrated Chandra & Jackson, 1971; Wilson & Pigden, 1964), but no significant improvement on the voluntary intake was achieved unless the treated material was supplemented with a source of nitrogen (Donefer, Adeleye & Jones, 1969). While Zafren (1960) used ammonium hydroxide (NH40H) as the treatment alkali, with the claim that the ammonium acetate resulting from the neutralization of the excess alkali could serve as an extra source of nitrogen in the treated straw, other investigators (Donefer et al. 1969) have adopted the method of supplementing the treated straw with a source of nitrogen. Since the efficiency with which dietary nitrogen is converted to microbial nitrogen in the rumen has a considerable influence on the efficiency the animal as a whole, studies herein reported were carried out to test the effectiveness with which rumen micro-organisms utilize different nitrogen sources in degrading cellulose in vitro.

Over a 12-day fattening period the use of maize in the poultry-fattening ration has no detrimental effect on the consistency of the body fat.

When fattening is rapid and live-weight gains are satisfactory, the type of fat deposited in the bird is harder than that laid down on a normal ration containing mixed cereals and a protein supplement.

The scheme of soil classification which finds most favour among scientists to-day has come from Russia and is the work of a band of brilliant and enthusiastic investigators whose labours have brought some order to what was otherwise chaos. The object of this communication is to endeavour to show how it is possible to modify the views of this school so as to make them apply to British conditions, and how the majority of British soils may be brought within the envisaged scheme.

1. A survey of commercial crops of spring oats suggested tilth as a major factor affecting emergence.

2. In field experiments conducted on clay and sandy soils, the surface tilth was regarded as a population of aggregates characterized by size which was analysed by means of a five-point quadrat. A tilth index was calculated from the data thus obtained. Under the rough tilths on the clay soil emergence and tilth were directly related, but on the sandy soil there was an optimum degree of cultivation, the plots with the finest tilth had been over-cultivated and gave a low rate of emergence (Fig. 2).

3. A greenhouse pot experiment examined the effect of a cover above the seed of 21 tilths, of varying proportions of 0·03–0·25 in., 0·25–1·25 in., 1·25–2·25 in. diameter aggregates, the soil below the seed being uniform in all treatments. This confirmed that emergence rates were higher under fine surface tilths than under very rough tilths (Fig. 3). An increase in the proportion of 0·03–0·25 in. fraction increased emergence regularly whereas an increase in the proportion of the 1·25–2·25 in. fraction reduced emergence regularly. The presence of 0·25–1·25 in. aggregates reduced emergence compared with that where 0·03–0·25 in. only were present, but the effect of an increase in the proportion was not regular (Fig. 4).

4. A second greenhouse pot experiment compared the effect of 3 tilths above the seed and 2 irrigation treatments. The low emergence rate (58%) caused by a very rough tilth under restricted irrigation was raised to 86% by liberal irrigation.

5. From the evidence of both pot experiments it is postulated that a covering tilth above the seed of 25% or more by weight of fine soil (0·03–0·25 in.) and not more than 40% of coarse aggregates (1·25–2·25 in.) will permit a rate of emergence of at least 80%.

6. As the fine covering tilths in the pot experiment gave high rates of emergence as compared with rougher tilths, it is suggested that the low rate of emergence, on the sandy soil field experiments, was due to a lack of soil moisture induced by over-cultivation.

Nitrosoguanidine-induced mutation frequencies for resistance to streptomycin, spectinomycin, erythromycin and novomycin were studied in Azospirillum brasilense. Lentil inoculated with A. brasilense and its mutants and Rhizobium strains produced increased nodule dry weight, nitrogenase activity of nodules and roots and grain yield compared with an uninoculated control.