Experiments were made between 1977 and 1979 to investigate the possibility of raising potato yields by mixing together cultivars having different growth patterns. The experiments also included mixtures of unsprouted and sprouted seed of the same or different cultivars. In the first experiment (1977) Pentland Crown was mixed with Arran Pilot, Red Craig's Royal or Désirée and the binary mixtures (1:1) compared with the pure stands of each. Yield of tubers from the mixtures did not differ significantly from the mean of two components planted alone at wide or narrow spacing of the seed tubers. Two experiments with identical treatments (1978) included mixtures of Majestic and Désirée and of each cultivar with unsprouted and sprouted seed. Mixtures (1:1) yielded more tubers than the mean of the two components planted alone and at final harvest in one experiment unsprouted and sprouted Majesties gave 7·6 t/ha more than the mean of these and 6·9 t/ha more than the more productive culture (P < 0·05). Similar differences were obtained in the second experiment.

In the final experiment (1979) the degree of sprout development at planting time was varied in the cultivar Majestic. Short or long sprouted seed was mixed with unsprouted seed and long sprouted Désirée was also mixed with unsprouted Majestic. Mixtures of the unsprouted cultivar with either long sprouted Majestic or Désiré exceeded, significantly, the mean yield of components planted alone by 4·1 and 5·8 t/ha, respectively, at a high level of fertilizer. As a mean of three experiments the mixture of sprouted and unsprouted Majesties yielded 6·26 t/ha more tubers than the mean of the components and 4·27 t/ha more than the higher yielding component in pure culture. Better light interception due to higher leaf area duration and a more persistent leaf canopy appeared to produce these effects.

The new model, described in a previous paper (Francis & Pidgeon, 1982), for estimating soil moisture deficits under cereal crops in Britain, was evaluated against experimental neutron probe data for eight test crops. The test crops covered a wide range within Britain of growing-season weather and soil types for both winter and spring cereals. Comparisons were also made with estimates of three other models, those of Ritchie, Rhoades & Richardson (1976), Jensen, Wright & Pratt (1971) and Smith & Douglas (1975).

The new model gives the best fit for six of the eight test crops, with root-mean-square errors (RMSE), taken over the whole season, of less than 10 mm of deficit and having small random bias. RMSE seldom exceeds 10 mm for any section of any season. By contrast, the other three models have whole season RMSE values in the range 10–40 mm. The model of Ritchie et al. (1976) generally overpredicted deficits early in the season and thereafter performed erratically; those of Jensen et al. (1971) and Smith & Douglas (1975) generally underestimated deficits. For two test crops where the new model performed poorly, serious inadequacies in crop growth and/or meteorological input data were identified as the reasons.

A sensitivity analysis for the new model emphasized the importance of the soil variables that were incorporated and the need for rudimentary crop growth information to supplement default assumptions.

It is concluded that the new model, having average RMSE values similar to expected neutron probe measurement errors, offers significant advantages over other models in estimation of soil moisture deficits. The new model could further provide a basis for extension to other crops or to description of the distribution with depth of soil moisture deficit.

The importance of a “well balanced” ration in feeding animals has long been recognised, and most intelligent stock-keepers pay some attention to the albuminoid ratio of the foods they use.

The changes in muscle protein and plasma radioactivity with time have been observed in anaesthetized pigs receiving constant infusions of [14C]glycine and [3H]tyrosine. The specific radioactivity of muscle protein was found to increase linearly with time. However, it was not possible to calculate absolute rates of muscle protein synthesis for the plasma radioactivity had not reached a plateau after 8 h infusion.

The specific radioactivities of Pietrain muscle protein increased more rapidly than those of Large Whites when animals of the same lean mass, receiving the same dietary amino acid supply per unit of lean mass, were compared. However, when considered with respect to published biochemical data, these results support the hypothesis that the differences arise from inequalities in plasma specific radioactivities; which appeared to be related to differences in blood volumes, between pigs of the two breeds, at the same age. When plasma specific radioactivity/time relationships were adjusted so as to account for this variation no significant differences were found, indicating that muscle protein synthesis and muscle growth proceed at similar rates in the two breeds.

1. The first lactation shews greater variability than the second, third, fourth or fifth.

2. The estimation of one lactation from another cannot be made with great accuracy, since the correlation coefficient between even successive lactations does not rise above + ·6.

3. It is necessary, in classing a cow, to decide on one lactation that shall represent her mature capability. It is suggested that the maximum lactation is the most suitable one to chose.

4. The correlation coefficient with the maximum lactation increases from ·394 for first to ·762 for fifth lactation.

5. The mean of the first and second lactations however gives a correlation coefficient of ·526 with maximum lactation, which is higher than any of the first three taken separately.

It has been shown that maize silage of good quality can be produced with losses of dry matter which are not necessarily much greater than those which characterise the production of oat and tare silage.

Excessive drainage of juice consequent on immaturity of crop contributes materially to the total loss of dry matter.

The main reason for the comparative failure of attempts in this country to produce maize silage successfully from the points of view of quality and economy lies probably in the general use of the late maturing variety, American Horse Tooth. Success will probably depend on growing a variety of maize which is able to reach a desirable stage of maturity under English conditions before being cut for the silo. Preliminary trials have indicated that the necessary qualities may be found in certain varieties like Saltzer's North Dakota, Longfellow, Compton's Early and White Cap, all of which mature at least a month before American Horse Tooth.

Seventeen tree species (16 legumes and Eucalyptus saligna) were grown for 4 years on an Ultisol of pH 4·5 at Nakau, South Sumatra, Indonesia. Leaf and wood yields were recorded seven times during the 4-year period and mineral and plant quality measurements were made on leaf samples from the first harvest taken 2 years after transplanting. At this time, leaf and wood yields were highest from Acacia mangium but the yield of this species declined over time. Highest leaf production was recorded for Cassia siamea over the 4-year period.

Mineral analyses of leaf indicated N, K, Ca and Mg to be adequate for animal production in all species. P was below the critical level for animals in all species and Na levels were adequate only in Acacia mangium and Acacia auriculiformis.

Plant quality measures (ADF, NDF, lignin) suggest marked differences could be expected in potential feed value between species through differences in voluntary intake and digestibility.

Sixteen Blackface wether lambs (25–27 kg) were fed for 9 weeks on diets based on either barley (B) or sugarbeet pulp (S), with either a low or high protein content. A constant amount of metabolizable energy (ME) was given at twice maintenance level. At one stage the animals were fed frequently and blood was sampled over a 24 h period. Plasma was assayed for acetate, glucose and insulin. After slaughter, the metabolism of acetate to CO2 and lipid was investigated in perirenal adipocytes in vitro.

Frequent feeding helped to achieve near-steady-state conditions. Carbohydrate source influenced plasma acetate (P < 0·08) but not glucose or insulin. Level of protein in the diet influenced plasma acetate, higher concentrations of acetate were associated with lower levels of protein (P < 0·01). Acetate oxidation and incorporation into lipid was influenced by the concentrations of acetate, glucose and insulin in the incubation media (P < 0·001). Acetate oxidation was influenced by carbohydrate source (P < 0·05), whereas level of protein in the diet affected acetate incorporation into lipid (P < 0·05).

These results show how the balance of nutrients provided to a ruminant for metabolism may influence selected plasma parameters and the metabolism of acetate by adipose tissue, which may help to explain the reduced efficiency of ME utilization from more fibrous diets.

Owing to the rapid rise in the price of linseed and linseed products during recent years, the question has arisen as to whether the farmer can grow linseed, for home consumption, at a smaller cost than he can buy it for under existing conditions. This question involves considerations as to which of the several kinds of linseed would be the most profitable to grow, and it becomes necessary to consider not only the agricultural requirements of the crop, but also the fact that the value of this crop is largely, if not entirely, determined by the quantity of oil produced per acre.

1. The exchangeable Fe, Al, Ca, Mg, K, Na have been determined in twenty soils from different parts of the East of Scotland, by extraction with N NH4Cl solution. Data on pH, “Lime Requirement” and loss on ignition are given for the sake of comparison.

2. Only three soils were found to contain Fe and Al in exchangeable form.

3. The content of exchangeable bases varies from 5·6 to 22·2 milligram-equivalents per 100 gm. air-dried soil.

4. The evidence is insufficient to deduce any definite relationship between pH and “Lime Requirement” and the pH cannot be correlated with the content of exchangeable bases except in the case of soils similar in character.

5. It is suggested that the differences in the relative proportions of the exchangeable bases indicate that there are on the one hand fundamental differences due to soil type and on the other hand fluctuating differences due to manurial treatment.

6. Emphasis is laid on the fact that the degree of saturation of a soil is not necessarily indicated by the content of exchangeable bases. At present the absorptive capacities of the soils examined are not known.

7. Until a sufficient number of soils have been examined and classified, it is unlikely that any satisfactory generalisation on the subject of exchangeable bases will be forthcoming.

Field bean varieties were grown for 2 years on five plots varying in pH from 4·7 to 8·4. Non-aggressive Chocolate Spot infection was shown to be greater on plants grown in soil of pH 4·7 and 5·8 than on those grown in soil of pH 6·7, 7·7 and 8·4. Seed weight per plant was greater on soil pH 7·7 than on soil pH 4·7, suggesting that acid soil reduced plant vigour and consequently increased disease susceptibility. Varietal differences in infection were shown, although absolute resistance was not observed. Varieties differed in their susceptibility on soils of varying pH, and also showed different stability for susceptibility over the varying environmental conditions.

The goal of the present study was to improve the CERES-wheat model simulation of grain protein concentration (GPC) for winter durum wheat and to use the model as a basis for the development of a GPC Simplified Forecasting Index (SFIpro). The performances of CERES-wheat, which is one of the most widespread crop simulation models, with (i) its standard GPC routine and (ii) a novel equation developed to improve the model GPC simulation for durum wheat, were assessed through comparison with field data. Subsequently, CERES-wheat was run for a 56-year period in order to identify the most important status and forcing variables affecting GPC simulation. The number of dry days during the early growth stages and the leaf area index (LAI; green leaf area per unit ground surface area) at heading stage (LAI5) were identified as the main variables positively correlated with CERES-wheat predicted GPC, and so included in the SFIpro. At validation against observed data SFIpro was found to perform differently on the basis of observed plant LAI. In fact, SFIpro was able to forecast GPC variability for intermediate values of LAI5 ranging from 1 to 2, while it totally failed when LAI5 was outside this range (LAI5 < 1 or LAI5 > 2). The results suggest that the relationship between LAI and GPC is not linear and that the model assumptions for GPC simulation in CERES-wheat are only partially confirmed, being valid for an intermediate range of LAI.

The objective of this meta-analysis study was to develop and validate equations estimated from in situ and in vitro methods to predict in vivo ruminal digestibility of organic matter (OM) of beef cattle diets. The database was composed of individual data of 23 diets from six experiments. Information collected from these studies was: in vivo digestibility and degradation parameters of OM calculated from in situ and in vitro incubations. The values of estimated times for the in situ and in vitro incubations to access in vivo digestibility of OM, and differences between degradation at 24, 48 and 72 h (in situ and in vitro) and in vivo digestibility were analysed in a model that included the fixed effects of forage neutral detergent fibre level. Thereafter, a multiple stepwise regression was carried out using OM digestibility as a dependent variable and degradation parameters (A = water-soluble fraction; B = potentially degradable water-insoluble fraction; and kd = degradation rate of fraction B) as independent variables. Equation validation was performed using data from a seventh experiment that have the same methods than previous studies. Stepwise regression results showed that the kd contributed significantly in most of the algorithms derived to predict in vivo digestibility. Validation analysis showed that equations developed from both in vitro and in situ incubations accurately estimated the in vivo digestibility of OM (P > 0.05). Our results suggest that equations developed to estimate OM digestibility showed both precision and accuracy; however, in situ method presented better results than in vitro.

Mineralized soil nitrogen (N) is an important source of N for grassland production. Some soils can supply large quantities of plant-available N through mineralization of soil organic matter. Grass grown on such soils require less fertilizer N applications per unit yield. A reliable, accurate and user-friendly method to account for soil N supply potential across a large diversity of soils and growing conditions is needed to improve N management and N recommendations over time. In the current study, the effectiveness of chemical N tests and soil properties to predict soil N supply for grass uptake across 30 Irish soil types varying in N supply potential was investigated under controlled environmental conditions. The Illinois soil N test (ISNT) combined with soil C : N ratio provided a good estimate of soil N supply in soils with low residual mineral N. Total oxidized N (TON) had the largest impact on grass dry matter (DM) yield and N uptake across the 30 soil types, declining in its influence in later growth periods. This reflected the high initial mineral N levels in these soils, which declined over time. In the current study, a model with ISNT-N, C : N and TON (log TON) best explained variability in grass DM yield and N uptake. All three rapid chemical soil tests could be performed routinely on field samples to provide an estimate of soil N supply prior to making N fertilizer application decisions. It can be concluded that these soil tests, through their assessment of soil N supply potential, can be effective tools for N management on grassland; however, field studies are needed to evaluate this under more diverse growing conditions.

1. As a result of soaking in water at body temperature (38° C), foods show variations in swelling ranging from approximately 10 per cent. to 260 per cent.

2. The volumes of equal weights of different foods after soaking also vary within wide limits. The percentages of moisture in the soaked foods show corresponding variations, being in some cases as high as those found in roots or green fodder.

3. These facts have led the authors to put forward a new conception of “bulk” in assessing the value of a ration.

4. Feeding experiments have been carried out to determine how far this factor of bulk is applicable in practice.

5. In the case of pigs of 40 to 80 lb. live weight, the bulk occupied by the foods did affect the quantity of food taken.

6. With calves, the swelling capacity of the concentrated food did not yield any definite results so far as food consumption was concerned.

Since behavioural adjustments are an important line of defence against thermal stress, either due to their energy efficiency or to efficiency at preventing overheating, we aimed to evaluate whether broilers fed different maize particle sizes adjusted their behaviour to deal with heat stress challenges. At several times a day, the behaviour of 220 naked neck broilers was evaluated. These broilers were fed with isonutritive diets containing maize with different geometric mean diameters (GMD): 605 and 2280 μm. The thermal environment was monitored during the experiment. Panting and open wings were the only behaviours that showed differences between the times of day (P < 0.05). However, GMD showed a significant effect on feed intake and panting (P < 0.05). The interaction between GMD and time of day was significant only on panting (P < 0.05). Although no daily variation was observed, the highest feed intake was observed in broilers fed the diet containing maize with a GMD of 2280 μm. Less than 5% of the broilers were observed drinking water during the day. Open wings was the behavioural adjustment most used by broilers from 10:00 h, and remained elevated until 14:00 h for both GMDs. The birds panted more when fed the diet containing maize with a GMD of 2280 μm. In conclusion, broilers adjust their behaviour to dissipate excess body heat from the environment and as a result of feed intake. Coarse particles of maize in the diet increase the thermal challenge of broilers since the environment also provides stressful thermal conditions.

The effect of glucagon on the rate of glucose production in the presence of alanine, of lactate and of propionate has been studied in isolated perfused livers obtained from foetal, suckling and weaned lambs.

Glucose utilization occurred in foetal livers in the absence of glucagon whereas addition of glucagon resulted in a net production of glucose from the three substrates. In livers from suckling and weaned lambs addition of glucagon was not essential for glucose production to occur and the stimulation of gluconeogenesis by added glucagon was less evident in the older lambs. The effect of glucagon was not dependent on changes in the rate of substrate uptake.

It is concluded that gluconeogenesis will be induced by glucagon in foetal lambs when their mothers are severely undernourished, and that placentally derived lactate could contribute up to 90% of the glucose synthesized.

Soil organic matter (SOM) is important for long-term crop productivity through maintenance of soil quality and is also now receiving attention due to its potential for climate change mitigation. The objectives of the present study were to investigate the effects of 9 years of fertilization on soil organic carbon (SOC) and total organic nitrogen (TON) and their fractions for the 0–50 cm profile in clayey (Luvisols) and sandy (Arenosols) soils in Murewa District, Zimbabwe. Three treatments were assessed: unfertilized (Control), nitrogen fertilizer (Nfert) and nitrogen fertilizer plus cattle manure (Nfert+manure). Density fractionation was used to assess the distribution of SOC and TON in three SOM fractions and their sensitivity to fertilization in fields 0–50 m away from homesteads (Homefields) and > 100 m away from homesteads (outfields). The relationship between light and heavy fraction organic carbon (C) were analysed to determine equilibrium levels that give an indication of carbon storage potential. In clayey soils total organic C under Nfert+manure was 4% higher than Nfert and 16% higher than the control. In sandy soils, SOC stocks were lowest in the control and highest in Nfert treatments at all depths. Nine years of fertilization significantly influenced SOC concentrations and storage up to 20 cm depth, below which stocks and concentrations of C and N were statistically insignificant. Distribution of C and N in density fractions showed greater stabilization under Nfert+manure in clayey soils, whereas it was greater under Nfert in sandy soils. Estimation of equilibrium levels suggested that homefields had potential to store more C, whereas outfields and control treatments had limited capacity due to attainment of lower equilibrium levels. Application of manure can be a low-cost alternative for enhancing soil quality and promoting soil C sequestration under conventionally tilled continuous maize cropping systems in Zimbabwe.

A flock of 320 Border-Leicester × Merino ewes was used to study the effects of pre-flushing and flushing treatments on subsequent lambing performances during the years 1958, 1959 and 1960. The flock was kept on non-irrigated perennial pastures in southern Victoria.

In 1958 groups of ewes that lost a mean of 17, 5 and 0 lb. during the 4 weeks immediately prior to flushing gave average lambing percentages of 94, 98 and 101, respectively.

In 1959 and 1960 flushing for a period of 3 weeks immediately prior to joining produced increased lambing percentages of 13 and 9, respectively. These increases were due almost entirely to increased twinning rates. The response to flushing was not related to the live-weight changes that occurred during flushing. However, the live-weights of the ewes at joining, and, to a lesser extent, before flushing, were related to subsequent lambing performances. The heavier ewes gave more twins than did the lightweight ewes.

1. Data from a long-term experiment providing information on the effects on barley of undersowing the crop with various common species of grasses and legumes are discussed.

2. There is no evidence that the yield of grain, yield of straw, 1000 grain weight or the nitrogen content of the grain was affected in any way by undersowing with any of these species.