Zinc deficiency is a common nutritional problem in calcareous agricultural soils, resulting in reduced crop yield and performance. The effects of zinc sulphate (0 and 40 kg/ha) on seed yield, its components and seed element contents of 21 wheat cultivars were investigated. Zinc sulphate application increased plant height, leaf area index (LAI), flag leaf area, biomass, spike length, number of seeds per spike, seed weight and harvest index (HI). The increase in HI indicates the greater effect of zinc on seed production compared to plant biomass. In most of the cultivars, zinc sulphate application decreased the content of phosphorus and nitrogen in seeds and increased the content of iron and potassium. The cultivars showed significant differences in all the traits measured, indicating the existence of genetic diversity in the cultivars studied. In the second year, which was hotter and drier than the first year, zinc sulphate application reduced the damage caused by drought and heat stress and improved seed yield and quality. The regression fit showed that newer cultivars had lower yields in unfertilized conditions compared to old cultivars and showed their superiority in zinc fertilized conditions. It seems that the newer varieties require more fertilizer because they have been bred on fertile soils.

Quantifying reasonable crop yield gaps and determining potential regions for yield improvement can facilitate regional plant structure adjustment and promote crop production. The current study attempted to evaluate the yield gap in a region at multi-scales through model simulation and farmer investigation. Taking the winter wheat yield gap in the Huang-Huai-Hai farming region (HFR) for the case study, 241 farmers’ fields in four typical high-yield demonstration areas were surveyed to determine the yield limitation index and attainable yield. In addition, the theoretical and realizable yield gap of winter wheat in 386 counties of the HFR was assessed. Results showed that the average field yield of the demonstration plots was 8282 kg/ha, accounting for 0.72 of the potential yield, which represented the highest production in the region. The HFR consists of seven sub-regions designated 2.1–2.7: the largest attainable yield gap existed in the 2.6 sub-region, in the southwest of the HFR, while the smallest was in the 2.2 sub-region, in the northwest of the HFR. With a high irrigated area rate, the yield gap in the 2.2 sub-region could hardly be reduced by increasing irrigation, while a lack of irrigation remained an important limiting factor for narrowing the yield gap in 2.3 sub-region, in the middle of the HFR. Therefore, a multi-scale yield gap evaluation framework integrated with typical field survey and crop model analysis could provide valuable information for narrowing the yield gap.

Two 10-day in vitro experiments were conducted to investigate the relationship between nitrogen (N) isotope discrimination (δ15N) and ammonia (NH3) emissions from sheep manure. In Exp. 1, three different manure mixtures were set up: control (C); C mixed with lignite (C + L); and grape marc (GM), with 5, 4 and 5 replications, respectively. For C, urine and faeces were collected from sheep fed a diet of 550 g lucerne hay/kg, 400 g barley grain/kg and 50 g faba bean/kg; for C + L, urine and faeces were collected from sheep fed the C diet and 100 g ground lignite added to each incubation system at the start of the experiment; for GM, urine and faeces were collected from sheep fed a diet consisting of C diet with 200 g/kg of the diet replaced with GM. In Exp. 2, three different urine-faeces mixtures were set up: 2U:1F, 1.4U:1F and 1U:1F with urine to faeces ratios of 2:1, 1.4:1 and 1:1, respectively, each with 5 replications. Lignite in C + L led to significantly lower cumulative manure-N loss by 81 and 68% in comparison with C and GM groups, respectively (P = 0.001). Cumulative emitted manure NH3-N was lower in C + L than C and GM groups by 35 and 36%, respectively (P = 0.020). Emitted manure NH3-N was higher in 2U:1F compared to 1.4U:1F and 1U:1F by 18 and 26%, respectively (P < 0.001). This confirms the relationship between manure δ15N and cumulative NH3-N loss reported by earlier studies, which may be useful for estimating NH3 losses.

Simplified cereal-based crop rotations are widely grown due to economic reasons, leading to the cultivation of wheat after wheat and associated yield losses. In this study, a crop rotation trial was conducted in Northern Germany on a Stagnic Luvisol from 2006 to 2018 with winter wheat after the four most widely used preceding crops in the region (sugar beet, winter wheat, silage maize and winter oilseed rape) in different crop rotations to evaluate potential benefits of different preceding crops. Additionally, the effects of two different sowing dates (2016–2018) and higher crop residue input (whole period) were investigated.

While the pre-preceding crop had no effect, preceding crops winter oilseed rape and sugar beet led to a significantly higher yield of about 1.00 and 0.43 t/ha, respectively, compared to wheat after wheat. This was not modified by crop rotational diversity, including wheat monoculture. Wheat yield tended to be higher for the late sowing date after sugar beet, maize and wheat, while there was no effect of sowing date after oilseed rape. Higher crop residue input led to a significantly higher yield (0.30 t/ha) in wheat after wheat (after pre-preceding crop sugar beet). Overall, sugar beet and winter oilseed rape were found to be favourable preceding crops for winter wheat under the given site conditions. The effect of sowing date on yield and potential modifications of the preceding crop effect by sowing date needs further research in appropriate long-term trials.

In tropical regions, water stress is one of the main causes of the reduction in forage productivity, and irrigation strategies can mitigate the problem, especially for highly productive species. The objective of this study was to evaluate the effects of irrigation, genotype and plant size on productive responses and water use efficiency (WUE) of elephant grass (Cenchrus purpureus [Schumach.] Morrone), in the rainy and dry season. The experimental design was randomized in blocks, arranged in split plots, the main plots were established based on the use of irrigation and the subplots were the tall-sized genotypes (IRI 381 and Elephant B) and dwarfs (Taiwan A-146 2.37 and Mott). The genotypes were evaluated for two years and harvested every 60 days. Water use efficiency, total forage accumulation per year and harvest, forage accumulation rate and forage density were evaluated. There was a significant difference between the genotypes in terms of total forage accumulated (P < 0.05). The most productive genotype was IRI 381, which showed the greatest total forage accumulation (42 168 kg of DM/ha in two years) in the irrigated plots. During the rainy seasons, IRI 381 stood out in terms of forage accumulated (24 667 kg of DM/ha). Irrigation favoured increases in forage accumulation around 60%, in both years of evaluation. Irrigation and plant size influenced the productivity and WUE of elephant grass harvested in 60-day intervals. Tall genotypes and Taiwan A-146 2.37 (dwarf size) stood out in most of the productive traits analysed, while Mott was highlighted by its forage density.

The possible adaptive significance of the occurrence of HK and LK red-cell types in Murrah buffaloes was investigated. Judged by haematological indices and thermorespiratory responses under conditions of moderate thermal stress, LK animals appeared to have a greater adaptive potential than HK animals in a hot arid environment. Dry matter percentage, packed cell volume (pcv), haemoglobin concentration (Hb), red blood corpuscles (RBC) and plasma protein values were significantly higher in LK-type animals. In addition, under identical conditions of thermal stress the LK animals exhibited significantly less rise in rectal temperature and respiratory rate than the HK animals.

It has been found from controlled environment studies that high temperatures lead todepressions in milk production (Johnson, 1965; Hafez, 1968; McDowell, 1972). Under outdoor situations where all climatic variables may act simultaneously on the animal, responses may vary from the classical chamber studies.

Relations were developed between the carrying capacity or production of fat-corrected milk (FCM)/ha and various measures of pasture growth for six pasture treatments grown in a subtropical environment. The pasture and animal production variables were obtained from pastures grazed on a weekly rotation using stocking densities which were varied so that a target weight of leaf material remained on the pasture at the conclusion of each grazing.

Within a treatment, there was a curvilinear relation between the rate of leaf growth and carrying capacity, with the greatest efficiency of conversion at the lowest leaf growth rates. This relation generally varied between pasture treatments because of differences in grazing intensity. There was little variation in the production of FCM per cow between grazing periods within a treatment, reflecting the experimental technique of matching the stocking density to the amount of forage. Consequently FCM/ha largely mirrored the stocking density with some adjustment for differences in production per cow caused by differences in grazing intensity between treatments. Production of FCM/ha was affected more by a unit change in residue leaf yield than by a unit change in leaf yield before grazing.

Using the rate of leaf removal (intake plus grazing losses) per cow as an inverse index of grazing intensity, it was apparent that the use of variable stocking densities to obtain specified residue yields after grazing did not necessarily equalize the grazing intensity because the rate of leaf removal per cow varied according to the before-grazing leaf yield. Also soiling by dung caused differences in the acceptability of forage for grazing, resulting in differences in grazing intensity between pastures with the same yield and stocking density.

1. An experiment was performed to compare some methods of supplying calcium to intensively kept chickens.

2. The calcium content of a mash was adjusted to contain low (0·13%), normal (1·16%) and high (2·14%) amounts, and each of these mashes was fed to groups of chicks having access to: (a) no grit, (b) flint grit alone, (c) limestone grit alone, (d) both flint and limestone grit.

3. The addition of flint grit significantly improved the efficiency of food utilization on all diets, whether limestone grit was provided or not.

4. On all three mashes the total amount of calcium grit consumed was greater in the presence of flint grit than when it was fed alone.

5. As the level of calcium in the diet increased, the amount of limestone grit consumed decreased, whether it was fed alone or in the presence of flint grit.

6. The best results, judged on a live-weight basis, were obtained when the normal calcium mash was fed with flint grit alone, followed by the low calcium mash with both flint and limestone grit, followed by the normal calcium mash with no grit.

7. On the basis of the efficiency of food utilization, the low calcium diet with flint and limestone grit was best followed by the normal calcium diet with flint grit alone.

8. Access to limestone grit reduced the efficiency of food utilization in all but the low calcium diet.

Two methods of determining the weight and one method of determining the volume of water imbibed by a soil have been discussed. The results of these methods have been shown to be concordant by an independent method.

The tentative conclusion reached is that the weight of water a soil imbibes can be readily determined by Fisher's method or from the Keen-Raczkowski box, but that the volume of imbibed water cannot yet be directly determined accurately.

A study has been made of variations in the shrinkage from the live pig to the carcass and from the carcass to the side of Wiltshire bacon. Most of the variation occurs at the first stage when the losses have a variance of 17·67 lb. compared with only 4·59 lb. and the second stage. Similarly, breed differences were found at the first stage, Wessex and Essex pigs giving 1·1 and 2·7 lb. more carcass respectively than the Large White pigs, but not at the second stage. On the other hand, differences between litter groups were found at both stages.

Correlations made between carcass measurements and yield of carcass and bacon were generally found to be small and positive. Antagonisms were indicated between quantity and quality of bacon, in particular by positive correlations between thickness of back-fat and weight of carcass, and between a desirable proportion of cuts and losses on slaughter. The problem of deciding the relative attention which should be paid to various carcass characteristics is discussed and the need for an index of total carcass merit is pointed out.

Frequently in near-infrared reflectance spectroscopy, a calibration is developed using very restricted data sets, e.g. material from one season, a small area or of a limited type: consequently, the predictions may have limited validity. This paper describes the use of both restricted and wide calibration sets for the prediction of crude protein in grass, silage and hay. Results show that predictions from the wider calibration sets are often as good as or better than predictions from restricted calibration sets. Therefore the use of wide calibration sets should be considered much more frequently in near-infrared reflectance.

1. The age of 210 days was selected for calf weight standardization. In general this is a preweaning weight under prevailing Jamaican conditions, and it represents a compromise between a very early age (90–120 days) which would reflect closely the milking ability of the dam, and the actual weaning age (approximately 260 days) when the grazing management of the herd would constitute a major unpredictable variable.

2. Either one or two weighings taken between the fourth and the ninth months of life was used to standardize calf weights to 210 days of age. In either instance for groups of calves, a mean estimate was derived which was very close to the actual mean 210-day weight, and which was suitable for data relating to groups of animals.

An experiment in which all combinations of four rates of N fertilizer soon after sowing, four in early spring and nine in late spring were applied to the same plots of winter wheat for 6 years is described and the effects discussed.

It was found that although the yield varied considerably from year to year the regime leading to greatest yield was fairly consistent. If the farmer had used the regime which gave the greatest average yield (0, 90, 180 kg N/ha in autumn, early spring and late spring, respectively) he would have averaged only 0·12 t/ha less than the maximum attainable each year.

Application of N increased protein concentration in the grain more or less linearly but the latest application increased it most. Since the regime which gave greatest yield on average produced grain which qualified for bread-making premium from the protein point of view in all years except 1981, adopting the regime which gave maximum yield would reduce the potential maximum gross margin by only £30/ha.

Analysis of the soil showed a reduction in pH down to 15 cm and of available P2O5 down to 10 cm.

As part of an ongoing investigation of ovine neuroendocrine mechanisms relating to photoperiod and eventually to wool growth, the diurnal variation of depilation force (an index of the strength of attachment of wool fibres to the skin of sheep) was investigated in Merino wethers and Border Leicester Merino ewes. Circadian rhythms were demonstrated in depilation force in both ewes and wethers. Further experiments were performed to investigate circadian endocrine rhythms which may have some bearing on the observed rhythm in depilation force. Circadian rhythms 180° out of phase with the depilation force rhythm were observed in plasma cortisol concentrations and in pineal serotonin N-acetyltransferase activities in Merino wethers.

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The thirty-ninth meeting of the group, chaired by Professor N. Crout of the University of Nottingham, was held in the Kohn Centre at the Royal Society, 6 Carlton House Terrace, London on Friday, 30 March 2007 when the following papers were read.