Experiments were conducted over the period 1987–94 at Cambridge University Farm and two other sites to examine the effect of various husbandry factors, particularly variety and irrigation regime, on rate, depth and density of rooting in potatoes. Maximum rooting depth ranged from 59 to 140 cm, indicating that potatoes can root to considerable depths and thereby have access to large volumes of water to satisfy the potential demand for water created by the atmospheric conditions and the size of the canopy. Root extension vertically through the soil profile was best described as a three-phase process: an initial rapid period lasting 3–5 weeks with growth rates c. 1·2 cm/day, a second period of slower growth (c. 0·8 cm/day), followed by cessation of root extension for the rest of the life of the crop. Variety had a major influence on the ultimate depth of rooting, primarily owing to variations in the length of the different periods of rooting rather than the rate in each period. It was observed that changes in the rate, or the cessation of root penetration were always preceded 4–9 days earlier by a change in the rate, or cessation, of leaf appearance. This feature should make it possible to characterize the duration of rooting of varieties through measurement of leaf emergence. Varieties which ceased leaf production early, such as Atlantic, were found to have a duration of root growth of c. 60 days, with Cara rooting for c. 30 days longer. Maximal total root length (TRL) and root length density (RLD) in the experiments reported were 16·9 km/m2 and 5·5 cm/cm3, respectively, similar to those found previously in potatoes and crops such as sugar beet, but considerably greater than many other vegetables. Rooting density decreased with depth, but the root systems were not as surface-oriented as many other studies have shown. When TRL was close to its maximum, the vertical distribution of RLD showed that between 40 and 73% was confined to the upper 30 cm, with irrigated crops possessing a greater proportion of their roots in the plough layer. Despite being planted in rows 70–91 cm apart, rooting systems were homogeneously distributed in a horizontal direction by c. 35 days after emergence, at which time the roots had reached a depth of c. 50 cm. Therefore, apart from a short period after emergence, the potato crop is capable of accessing considerable volumes of soil from which to extract water and nutrients. Ensuring that soil conditions are conducive to maximal rates of root growth should be the target for growers, since this will lead to a more efficient use of soil water and irrigation.

A rotation experiment was conducted on an alluvial soil at Central Potato Research Station, Jalandhar, India between 1994 and 1999 to develop an integrated nutrient management programme for a potato–sunflower–paddy rice rotation. It tested 10 fertilizer treatments that combined application of 50, 100 and 150% of the recommended rates of inorganic nitrogen (N), phosphorus (P) and potassium (K) with farmyard manure (FYM) and in some cases zinc. Potatoes were the most nutrient-responsive crop followed by paddy rice and sunflower. The responses of potatoes to both P and K were greater in frost and late blight years. In these experiments potatoes required NPK at 150% of the currently recommended rate for maximum tuber production (i.e. they required 270 kg N, 52 kg P and 150 kg K/ha). Application of FYM at 30 t/ha with 270 kg of inorganic N/ha (FYM+N) was less effective than the use of NPK at 150% of the currently recommended rate. Application of K to replace that removed in the harvested crop was more effective in potatoes than giving K at 100 or 150% of the currently recommended rate.

Sunflowers grown after potatoes that had received NPK at 150% of the currently recommended rate or with the FYM+N treatment required only half of the currently recommended rate of NPK for maximum yield (i.e. they required 23 kg N, 7 kg P and 13 kg K/ha), whereas paddy rice, grown as a third crop, required the full amount of NPK at the currently recommended rate (i.e. 120 kg N, 26 kg P and 67 kg K/ha). Application of K to adjust for its removal did not benefit sunflowers or paddy rice. Zinc had no direct effect on potatoes or any residual effects on the succeeding sunflower and paddy rice crops. The effects of the FYM+N treatment were cumulative, especially on potatoes which were the most responsive crop, whereas those involving the application of NPK at 150% of the currently recommended rate were not. Also, the NPK fertility of the soil was enhanced and more organic carbon was present following the FYM+N treatment than with NPK fertilizers applied at the currently recommended rate. Application of P resulted in a build-up of P but none of the treatments, even the applications of K to adjust for its removal, maintained the K status of the soil at its initial level.

Experiments were conducted in Bangkok clay soil to investigate the influence of planting date, tiller separation and plant density on the yield and yield attributes of parent and clone plants of two transplanted rice varieties. The 15 July transplanting of mother crop and collected vegetative tillers and retransplanting on 15 August showed significantly high grain yield (3·8 t/ha). The photoperiod-insensitive variety RD23 gave higher yield (3·8 t/ha) than the photoperiod-sensitive variety KDML105 (3·0 t/ha). Tiller separation up to 4 tillers/hill did not adversely affect the mother crop. Vegetative tillers transplanted with 2–4 tillers/hill gave a similar yield as the mother crop in both the seasons. Vegetative tillers gave a higher yield than nursery seedlings transplanted on the same date. The yield components, i.e. weight of 1000 grains, grains/panicle and per cent filled grains, showed better responses with early transplanting of KDML105 in the mother crop and vegetative tillers except for panicle number and panicle length of vegetative tillers with RD23. The results suggest that in some flood-prone lowlands, where the transplanted crop is damaged by natural hazards, vegetative propagation using tillers separated (maximum 4/hill) from the previously established transplanted crop is beneficial for higher productivity.

CERES-Rice model was used to simulate growth and yield of four common rice varieties in Thailand with the attention on rate and timing of N application, a factor that most limits crop yield. The model predicted slightly higher grain yield than that observed for all varieties at N input of 75 kg/ha, but the differences between observed and simulated yields were not significant, except for varieties HSP and SPR90. The simulated grain[ratio ]straw ratio was significantly higher than the observed value for all varieties except that of HSP. There was no significant difference between the simulated and observed values of days to flowering. Generally, the model reasonably predicted the phenology and yields of RD23 and KDML105 varieties. The model was also used to compare the yields of KDML105 variety as influenced by rate and timing of N application grown in acid sulphate soils. There was a variation in predicted biomass yield with applied N rates at 0 and 150 kg/ha, but timing of application had no effect. In Aeric Endoquept and Sulfic Tropaquept soils at Suphan Buri and Pathum Thani rice research stations, the yield patterns remained unchanged and showed a positive response to N rate up to 75 kg/ha. The model estimated higher grain yields beyond 75 kg N/ha while the observed yield decreased. Based on the simulated yields for a 10-year period at the Asian Institute of Technology (AIT), Pathum Thani, Suphan Buri, Nakhon Pathom and Ratcha Buri rice research stations the varieties were ranked as: SPR90 > RD23 = HSP > KDML105. The model suggested that SPR90 is the most suitable variety for the central plain and its potential yield ranges from 4030 to 5600 kg/ha. Pathum Thani province, with acid sulphate soils, had the lowest potential for rice production.

Honeycomb selection in the F2 generation of maize (Zea mays L.) hybrid PR 3183, based on line performance per se in the absence of competition, led to recycled hybrids with improved potential yield per plant (mean yield per plant in the absence of competition). In the present study six S6×S6 recycled hybrids and two commercial single-cross hybrids (PR 3183 and B73×Mo17) were tested at three plant densities (25000, 41667 and 83333 plants/ha), in two locations (Technological Education Institute farm of Florina, Greece and University farm of Thessaloniki, Greece), for 2 years (1998, 1999). The study was undertaken to assess indirectly the potential yield per plant (p), the crop yield potential (Ymax), and the optimum plant density (Dopt) of the hybrids. Estimate of p and Ymax were obtained through linear regression analysis of yield per plant (Yp) on plant density (D), expressed by the equation Yp = p−qD, with Ymax being equal to (1/4)p2q−1. Optimum plant density was assessed through linear regression analysis of natural logarithm of yield per plant on plant density, expressed by the equation ln(Yp) = α−bD, with Dopt being equal to 1/b. The recycled hybrids had higher estimated potential yield per plant (p), than the two check hybrids, with p values being positively correlated with yield per plant of hybrids obtained experimentally in the absence of competition. Results indicated that the higher potential yield per plant decreases the optimum plant density, and renders the hybrids less density-dependent.

Effects of nitrogen fertilization (80 kg N/ha) were studied on pearl millet (Pennisetum glaucum) genotypes including hybrids (MH-179 and HHB-67), composites (CZ-IC-923 and CZP-9604) and land races (Barmer population and CZ-IC-718) grown for 2 consecutive years (1997 and 1998) under rainfed conditions of the Indian arid zone. Nitrogen application significantly increased the grain and stover yields in all the genotypes, particularly in the hybrids during both the years but more so in 1997, characterized by late onset of rains followed by adequate precipitation (299·5 mm). Notwithstanding lower plant water potential and leaf relative water content, N fertilized plants displayed significantly higher photosynthetic rates, leaf area, levels of total chlorophyll, starch, reducing sugars, soluble protein and free amino acids and nitrate reductase activity as compared with unfertilized control plants in all the genotypes during both the years.

Genotypes HHB-67 and Barmer population during 1997 and HHB-67 and CZ-IC-718 during 1998 provided significantly higher grain yields than other genotypes whereas dry matter production was highest in cv. Barmer population during both the years. These genotypes generally maintained higher rates of photosynthesis, more efficient carbohydrate metabolism and higher nitrate reductase activity leading to better performance. Relatively higher yields of land races than composites and comparable with those of hybrids indicated adaptation of these cultivars to arid conditions and maintenance of several characteristics for their superior performance which could be further augmented by N application.

Fertility induced improvement of metabolic efficiency, coupled with higher photosynthesis and nitrate reductase activity for efficient N utilization seem to be the control mechanisms, for enhanced growth and yield of diverse pearl millet genotypes under limited water conditions.

In order to understand better the factors which influence the persistence or non-persistence of Lolium perenne and Trifolium repens on damp hill land in a wet climate, swards in mid-Wales which had been converted from semi-natural rough grazing (predominantly Molinia caerulea or Nardus stricta or Agrostis/Festuca/Nardus) in 1961–81 were examined in 1982 and 1999, using a point quadrat technique.

There was a marked decline between 1982 and 1999 in the proportion of L. perenne in the majority of the study areas. On the other hand, in 1999 the oldest swards (sown 30–38 years before) contained at least as high a proportion of L. perenne (22% of sward on average) as the younger swards (sown 18–29 years before). In two swards sown 25–26 years before, at 390–445 m above sea level, which received 95 kg N/ha per year, L. perenne was 36% of sward. On the other hand, no L. perenne was recorded on three swards which were no longer receiving fertilizer and which were being grazed at a greatly reduced stocking rate. The proportion of T. repens was rather low and declined between 1982 and 1999 (from 10 to 4% of sward on average). The application of more lime and more K and perhaps less N would probably have increased the proportion of T. repens. On at least one farm, the use of MCPA against Cirsium spp. had probably reduced the proportion of T. repens. There were positive correlations between the proportion of L. perenne and the proportions of T. repens and Poa spp. There were negative correlations between L. perenne and each of Agrostis spp., Festuca spp. and Holcus lanatus and also between T. repens and Agrostis spp. The proportion of Poa spp. was positively correlated with exchangeable Ca, nitrate-N and total N in soil and negatively correlated with exchangeable acidity.

Genotype–environment interaction and yield stability were evaluated for 19 genotypes of lovegrass (Eragrostis curvula). The study was conducted in the central semi-arid region of Argentina. Three locations and two growing seasons in combination generated six environments. Genotypic responses and stability of yield under variable environments were investigated. The genotype–environment interaction was analysed by three methods: regression analysis, AMMI and principal coordinates analysis (PCO). Analysis of variance showed that effects of genotype, environment and genotype–environment interaction were highly significant (P < 0·01). The genotypes accounted for 20% of the treatment sum of squares, with environment responsible for 65% and interaction for 14·5%. The biplot indicated that there was partial agreement between the AMMI and regression model. However the scatter point diagrams obtained from PCO analysis revealed only limited agreement with the results obtained by the regression analysis and the AMMI model. The results show that the AMMI model as a whole explained twice as much of the interaction sum of squares as did regression analysis and was more adequate than PCO analysis in quantifying environment and genotype effects for forage yield. AMMI analysis of the genotype–environment interaction effects showed that there were responses characteristic of a particular location. This type of association implies some predictability of genotype–environment interaction effects on forage yield production when differential responses across genotypes are associated with locations. Environmental factors may contribute to the interpretations of genotype–environment interaction. However in the semi-arid region, where fluctuations in growing conditions are unpredictable, additional research is required to obtain an integration of interaction analysis with external environmental (or genotypic) variables.

Dried lucerne (Medicago sativa), dried Italian ryegrass (Lolium multiflorum) and wheat (Triticum aestivum) straw, in the latter case supplemented with soyabean meal, were each fed to cattle, sheep and rabbits in each of 2 years. In both years, plant parts of the three diets were tested for in vitro digestibility, in both milled and chopped (1 cm lengths) form, and for cell wall content (as NDF). In the first year, the plant parts were analysed for lignin and both the plant parts and the faeces were examined microscopically for the proportions of thick-walled, thin-walled and epidermal cells in cross-sectional area and for the thickness of the cell walls.

The plant parts with the lowest proportion of thick-walled cells in cross-sectional area (0·05) were the lucerne leaflets and those with the highest proportion of thick-walled cells (0·68) were the stems of wheat straw. The cell walls of the thick-walled tissues were thinnest (0·7–0·8 μm) in Italian ryegrass leaf blades and sheaths. Within each cell type for the whole crop, the order of cell wall thickness was wheat straw > lucerne > Italian ryegrass. In vitro digestibility of DM was lower (by 0·031–0·085 g digestible DM/g total DM) in chopped than in milled stems of lucerne, ryegrass and wheat and in leaf sheaths of wheat. This suggests incomplete and/or delayed access of rumen microorganisms to some of the cell wall in chopped material in vitro and probably, therefore, also in chewed material in vivo. The concentrations of NDF and lignin in both ryegrass and wheat were in the order leaf blades < leaf sheaths < stems.

The lucerne crops were more mature than the ryegrass crops and there was no consistent difference between lucerne and ryegrass in intake of DM or intake of NDF. The intake of wheat straw DM was 0·52 that of lucerne and ryegrass, whereas the intake of straw NDF was 0·89 that of lucerne or ryegrass NDF. Intake of both DM and NDF in relation to metabolic body weight was highest (87–93 g DM and 45–48 g NDF/kg W0·75) with cattle on lucerne and ryegrass and rabbits on ryegrass and lowest (33–34 g DM and 29–30 g NDF/kg W0·75) with sheep and rabbits on straw. The output of faeces/kg W0·75 was particularly high (38–41 g DM and 30–32 g NDF) from rabbits fed lucerne or ryegrass. Digestibility of DM was highest (0·726–0·732 g/g) with cattle and sheep fed ryegrass, followed by cattle and sheep fed lucerne and sheep fed straw. Digestibility of NDF was highest (0·708–0·752 g digestible NDF/g total NDF) with cattle and sheep fed ryegrass and sheep fed straw. Digestibility of NDF with rabbits was lower than with cattle or sheep, but was higher than might have been expected, in a small, hind-gut fermenter, with ryegrass (0·339 g/g) and straw (0·492 g/g).

The proportion of thin-walled cells was much lower in the faeces than in the diets, but there was an appreciable proportion (0·10–0·27) of these cells in the cross-sectional area of faecal particles. The cell walls of all cell types were thinner in the faeces than in the diets, e.g. those of the thick-walled cells were thinner by 0·35 μm in lucerne, by 0·11 μm in Italian ryegrass and by 0·41 μm in wheat straw. The faeces from rabbits had higher proportions of thick-walled and epidermal plant cells in cross-sectional area, and a lower proportion of thin-walled cells, than the faeces from cattle and sheep.

To identify separate effects of gender, castration and exogenous oestrogen on growth, castrated lambs of both sexes and entire male lambs (n = 8) were implanted subcutaneously with three sizes of oestradiol-17β implants, or not implanted, and grazed on ryegrass and white clover pasture for 180 days. A group of non-implanted entire female lambs (n = 8) was run together with the others. Non-implanted entire male lambs grew faster, had heavier heads, less internal, non-carcass fat and more protein and less fat and water in the carcass than non-implanted entire females. In addition, they had higher 12th vertebral spine, thicker tibia, and heavier and larger humerus than entire female lambs. Castration of male lambs reduced live-weight gain, weight of head and content of protein in the carcass whereas it increased carcass fat content. In addition, it caused lengthening of cannon bones and reduced height of 12th vertebral spine and length of tibia. In females, gonadectomy increased height of 12th vertebral spine and diameter to length ratio of the radius. Oestradiol treatment increased live-weight gain, reduced total internal and carcass fat, and increased water and protein content of the carcass in gonadectomized animals of either sex, and increased weight of carcass and head in spayed ewe lambs. Oestradiol treatment inhibited longitudinal growth of cannon bones and stimulated that of vertebral column and ribs, but had little effect on the dimensions of limb bones apart from increasing their diameter. Oestradiol treatment had no effect on muscle length but increased muscle girth and weight, except for m. splenius in ram lambs where muscle weight was reduced. Effects of oestradiol on skeletal measurements in most cases were linearly related to dose of oestradiol. It was concluded that the variable effects of sex steroids on the skeleton were related to the differential pattern of skeletal maturation. In early maturing bones acceleration of the growth process by an exogenous sex steroid caused elongation to cease prematurely, whereas in late-maturing bones the acceleration effect on elongation did not result in premature cessation. This observation may explain the often contradictory reports in the literature on the effects of sex steroids on linear growth of bone.

Genetic parameters were estimated for purebred and crossbred lambs of a local breed using a single trait animal model. The traits recorded were: birth weight (BWT), weight at 30 days (WT30), weaning weight (WWT), average daily gain from 1 to 30 days (ADG1) and average daily gain from 30 to 90 days (ADG2). Five different animal models were fitted for each trait; all including additive direct genetic variance and various combinations of additive maternal and environmental maternal effects. The most appropriate model was chosen based on likelihood ratio tests. Additive maternal and permanent environmental effects were important (P < 0·05) for birth weight in purebred and crossbred lambs, when compared with a model containing only additive direct effects. Inclusion of maternal permanent environmental effects provided a better fit (P < 0·05) for weaning weight in purebred lambs than a model containing only additive direct effects. Estimates of heritability from the model containing additive direct, maternal effects and maternal permanent environmental effects, but not additive direct-maternal correlation, for combined purebred and crossbred lambs were 0·32 for BWT, 0·19 for WT30, 0·24 for WWT, 0·26 for ADG1 and 0·12 for ADG2. Estimates of additive maternal and maternal permanent environmental variances, respectively, as a proportion of phenotypic variance were 0·06 and 0·07 for BWT, 0·05 and 0·02 for WT30, 0·02 and 0·03 for WWT, 0·03 and 0·05 for ADG1 and 0·00 and 0·03 for ADG2. Estimates of direct-maternal correlation in subsequent analyses were significant and ranged from −0·16 to −0·95 for live weights and from −0·73 to −1·0 for daily gains. However, the very large negative correlations probably resulted from undefined non-genetic covariances as well as possible antagonistic genetic effects. These results indicate that it would be possible to improve growth traits in a local sheep breed through genetic selection.

Progress in politics and science often happens by accident. The unforeseen impact of the foot and mouth epidemic may fall into this category. Both the Ministry of Agriculture and vets were over-stretched dealing with the crisis and so badger culling, which was to have resumed on 1 May 2001, was suspended for a year; even routine TB testing of cattle is on hold.

It seems probable that the Krebs/Bourne badger culling trial will be abandoned altogether. At least seven of the ten ‘triplet’ badger cull areas have been disrupted, particularly in Devon/Cornwall and Gloucestershire/Hereford. Some 600 of the 2900 badgers culled were in these two areas, perhaps 120 with TB, but only some 25 infectious. Since these were from some 400 km2, encompassing 450 farms, it is hard to see how the culls will have made the slightest impact on cattle TB.

In fact it is already apparent that each TB badger has cost some £35000, which merely confirms the 1986 findings of the Dunnet Review that badger culls are a waste of money because they do not work. Professor McInerney, as part of the review, noted that ending badger culling was purely a political decision. If Labour had won the 1992 election, contingency plans were in place to end culls, but, sadly, by 1997 ‘New’ Labour decided it was politically safer to go ahead with the Krebs cull. Enough data ought to be available from the trial to concoct ‘scientific’ reasons to grasp the nettle and take the inevitable and long overdue decision politically to end this sorry farce, once and for all.