Soil erosion in a field in north Norfolk is described. Gullies formed, one up to 2 m deep, 5 m wide and 214 m long, and from this gully about 450 t of soil was eroded. Other gullies and rills deposited about 275 t of soil. In the large (61 ha) field the area subject to erosion was small, about 2·5%. The soil, slope, cultural and rainfall factors which caused erosion are discussed. Erosion in this field is not a rare phenomenon and crop yields will be affected if erosion continues. A solution to the problem is suggested.

The development of stable suckling order, the incidence of fighting when suckling, weight gain during the suckling period, and the severity of facial wounding were studied with litters of piglets in which the canine and lateral incisor teeth were either clipped at birth or left intact. Facial wounding was largely confined to litters with unclipped teeth. Severity of wounding correlated with the observed incidence of fighting on the udder (P<0·01); and both wounding and fighting were more common among litters comprising a large number of piglets (P<0·05). When the effect of litter size was taken into account, there were no substantial differences in weight gain to 3 weeks between piglets with high and low scores for facial wounding, nor between clipped and unclipped litters. Piglets which habitually occupied the most anterior or most posterior teats had less facial wounding than middle-suckling piglets, and showed greater consistency in teat choice. No gross differences between clipped and unclipped litters were observed in the development of stable suckling order during the first week of life. It is concluded that the ‘eye’ teeth, although used in disputes over teat choice, have little influence on the frequency of such disputes or on the original development of stable suckling order.

Multi-environment trials (METs) in West Africa have demonstrated the existence of genotype×environment interactions (G×E), which complicate the selection of superior cultivars and the best testing sites for identifying superior and stable genotypes. Two powerful statistical tools available for MET analysis are the additive main effects and multiplicative interaction (AMMI) and the genotype main effect+G×E (known as GGE) biplot. The objective of the present study was to compare their effectiveness in identifying maize mega-environments and stable and superior maize cultivars with good adaptation to West Africa. Twelve extra-early maturing maize cultivars were evaluated at 17 locations in four countries in West Africa from 2006 to 2009. The effects of genotype (G), environments (E) and G×E were significant (P<0 01) for grain yield. Differences between E accounted for 0 75 of the total variation in the sum of squares for grain yield, whereas the G effects accounted for 0 03 and G×E for 0 22. The GGE biplot explained 0 74 of total variations in the sum of squares for grain yield and revealed three mega-environments and seven cultivar groups. The AMMI graph explained 0 13 and revealed four groups each of environments and cultivars. The two procedures provided similar results in terms of stability and performance of the cultivars. Both methods identified the cultivars 2004 TZEE-W Pop STR C4 and TZEE-W Pop STR C4 as superior across environments. Cultivar 2004 TZEE-W Pop STR C4 was the most stable. The GGE biplot was more versatile and flexible, and provided a better understanding of G×E than the AMMI graph. It identified Zaria, Ilorin, Ikenne, Ejura, Kita, Babile, Ina and Angaredebou as the core testing sites of the three mega-environments for testing the Regional Uniform Variety Trials-extra-early.

When 15N is used to trace the fate of N fertilizer applied in spring to winter wheat crops, some is not recovered in the crop or the soil and has to be presumed lost. In 13 experiments made from 1980 to 1983 on three widely differing soils, these losses ranged from 1 to 35%. We partitioned them between leaching and denitrification by using models to estimate the loss by leaching, talcing into account the N absorbed by the crops, and subtracting this loss from the total loss to obtain the apparent percentage loss by denitrification, LDN. An analysis of variance showed that LDN increased significantly with the quantity of N applied, so the study considered LDN values for a standard N application of 150 kg/ha subsequently. Regressions showed that LDN was better related to the wetness of the soil during the 3 weeks after fertilizer application than to the corresponding amount of rain, as would be expected for denitrification. Values of LDN could not, however, be satisfactorily related to soil temperature, probably because the range of temperatures was too narrow. The apparent losses by denitrification were, on average, nearly twice as large as those by leaching, but the ratio varied greatly between experiments.

Growth and yield components of a semi-dwarf spring wheat (Triticum aestivum L., cv. GWO 1809) were determined under three different atmospheric CO2a concentrations (350, 675 and 1000 μ1/1) in controlled environment chambers of the Duke University Phytotron. CO2 enrichment enhanced tiller and head emergence and increased the number of head-producing tillers and the total dry weight of the plants. Total leaf area, stem height and root/shoot ratio of the plants were greater at high CO2 concentrations than at low. Net assimilation rate (NAR) increased with increasing CO2 concentration and decreased with plant size. There was little effect of CO2 enrichment on leaf weight ratio (LWR) and leaf area ratio (LAR) and no significant effect on specific leaf area (SLA). The weight and number of seeds were significantly higher with increasing CO2 concentration. The results of this study provide evidence that important changes in plant growth and development may occur during the next century if global CO2 enrichment continues. Some of these changes would have important ecological impact in natural and managed ecosystems in the future.

Sheep prepared either with a rumen cannula, or with a rumen cannula plus re-entrant cannulae in the duodenum and ileum were fed fresh ‘Ruanui’ perennial ryegrass (R), ‘Manawa’ short-rotation ryegrass (M) and white clover (C) at dry-matter intakes ranging from 450 to 1000 g/24 h. Paper impregnated with chromic oxide was given once daily via the rumen fistula as a marker.

Amounts of Mg, Ca, P, K and Na entering and leaving the small intestine and excreted in the faeces were regressed against the intake of each element for each sheep and these equations (all, other than the faecal excretion of Na, significant (P < 0·05)) were used to calculate the extent of apparent absorption or secretion in the stomach, the small intestine and the large intestine at two levels of OM intake (500 and 800 g daily).

Quantities of Mg (at high intake), Ca and K (except sheep fed M) leaving the stomach were significantly lower (P < 0·05), while the amounts of P and Na were significantly higher (P < 0·01) than the amounts consumed. Quantities of Mg (at high intakes) and Ca leaving the small intestine were significantly higher (P < 0·05) while amounts of P, K and Na (at high intakes) were significantly lower (P < 0·05) than the corresponding quantities entering the small intestine. At both intakes in the case of Na and at the higher intakes in the case of the other mineral elements, quantities of Mg, Ca (except sheep fed C), P, K and Na excreted in the faeces were significantly less (P < 0·05) than the amounts entering the large intestine.

Thus at the higher intakes there were net absorptions of Mg, Ca and K (except sheep fed M) from, and net secretions of P and Na into, the stomach. The small intestine was the major site of net absorption for P and K and a minor site for Na, while a net secretion of Mg and Ca occurred into this region. Net absorption of Mg, Ca, P, K and Na occurred from the large intestine at the higher intakes.

The retention of Mg, Ca and P is discussed in relation to the animals' minimal daily requirements of these elements.

The soil water regimes, flow paths of water and concentrations of nutrients in this water were measured for a clay soil growing winter wheat in 1978–9 and 1979–80. The soil was either drained with mole drains at 2 m spacing connected to plot drains 46 m apart or undrained. In the 1st year a compacted layer at about 20 cm depth caused a perched water table in the Ap horizon in both drainage treatments, and prevented the mole drains at 60 cm from affecting the water table. In 1979–80 after cultivation to disrupt the compacted layer, midway between the mole drains the depth to the winter water table was 20 cm greater than in undrained soil.

Surface flow, interflow at the depth of the plough layer and deep drainflow from mole and pipe drains responded rapidly to winter rainfall events. During both winters the mole and tile system removed most of the rainfall on the drained plots and the peaky hydrographs were typical of a mole system in a clay soil. In the undrained plots only a small proportion of the winter rainfall was accounted for in flow from the top 30 cm, and up to 75% of the water was able to percolate downwards possibly to below the barriers that separated the plots. Long-term water-balance studies indicated that a proportion of the water moving to depth in the undrained plots was probably entering the deep drainage system of the drained plots. As a result, the mole and pipe drainage system often removed more water than the rainfall input less evapotranspiration. This problem did not affect the depth to the water tables.

For each flow component concentrations of nitrate, ammonium, nitrous oxide, phosphorus, potassium and calcium were measured in the drainage water. Concentrations of nitrate-N from all drained plots were largest in autumn, being in the range 50–95 mg N/1, but then decreased to 1–5 mg N/1 by the end of March. Losses of nitrate-N were mainly through the mole drains and amounted to 43·6 and 59·7 kg N/ha in the 2 years. The quantities of nitrate-N lost in surface runoff or in flow in the cultivated layer were small on both treatments. Gaseous nitrous oxide, ammonium and phosphorus contents were very small. Potassium concentrations were somewhat larger, but not exceeding 3·5 mg/1. The calcium concentrations were in the range 40–210 mg/1. Concentrations of herbicides measured in November 1980 were negligible.

In the 2nd year water was taken up from a greater depth in the drained than in the undrained plots from April onwards. These results are discussed in relation to water supply to the crops at this site.

Two field experiments in Canterbury, New Zealand, were conducted during 1993–95 following the ploughing of temporary pasture leys. These experiments investigated the effects of cover crop management on the accumulation of soil mineral N and nitrate leaching during winter, and the growth and N uptake of the following spring cereal crop. The cover crops used were ryegrass (Lolium multiflorum L.), oats (Avena sativa L.), lupins (Lupinus angustifolius L.), mustard (Sinapis alba L.) and winter wheat (Triticum aestivum).

Ploughing of temporary pasture in autumn (March) resulted in extensive net N mineralization of organic N by the start of winter (June). In fallow soil, mineral N in the profile in June ranged from 98 kg N/ha in 1993 to 128 kg N/ha in 1994. When cover crops were established early in the autumn (March) in 1993, both the above-ground dry matter production (1440–3108 kg DM/ha) and its N content (50–71 kg N/ha) were substantial by the start of winter. In 1994, establishment of cover crops one month later (April) resulted in very little dry matter production and N uptake by June. In both years, compared with fallow soil, winter wheat planted in May had little effect on soil mineral N content by the start of winter.

Compared with fallow, cover crops had little effect on soil drainage over winter. Cumulative nitrate leaching losses from fallow soil were much smaller in 1993 (23 kg N/ha) than in 1994 (49 kg N/ha), mainly due to differences in rainfall distribution. Cover crops reduced cumulative nitrate leaching losses in 1993 to 1–5 kg N/ha and in 1994 to 22–30 kg N/ha. When cover crops were grazed, soil mineral N contents were increased due to the return of ingested plant N to urine patch areas of soil. Elevated soil mineral N contents under grazing persisted throughout the winter. Grazing had little effect on cumulative nitrate leaching losses, mainly because of the small amount of drainage that occurred after grazing in either year.

Compared with fallow, incorporation of large amounts of non-leguminous above ground dry matter depressed the yield and N uptake of the following spring-sown cereal crop. Where cover crops were grazed, yields of the following cereal crops were similar to those for soil fallow over the winter.

1. Herring-meal supplements fed to sheep on a basal diet low in protein were more effective than casein supplements in promoting nitrogen retention and growth.

2. The herring-meal supplements caused less extensive formation of ammonia in the rumen than did the casein supplements. This is considered responsible for the differences found in the value of the proteins.

3. Meat from the sheep fed herring meal was not tainted in flavour.

4. The use of formaldehyde to preserve herring before making them into meal had no deleterious effects when the meal was fed to sheep.

Metabolite production rates were determined in the portal vein and hepatic veins of catheterized adult dairy cows maintained under normal conditions of husbandry. The production rates were calculated from the metabolite concentrations in arterial, portal and hepatic-venous blood, and from the rates of blood flow in the portal vein and the hepatic veins. In general, qualitatively similar metabolite production was observed in three non-lactating and two lactating cows, but production rates tended to be higher in the lactating cows due to higher blood flow rates.

About half the lactate utilized by the liver was absorbed from the gut, while the other half was derived from endogenous sources. Lactate absorbed from the gut was quantitatively of less significance than propionate as a substrate for hepatic metabolism. Even in cows that were well fed, there was a net production of ketone bodies from the liver that was almost as great as the net production from the gut. However, while the liver produced D-3-hydroxybutyrate it took up acetoacetate. In the lactating cows, acetate, propionate and butyrate were absorbed from the gut in the proportions of 9·5:2·5:1, respectively. About 90% and 80% of the absorbed propionate and butyrate, respectively, were taken up by the liver.

On the routine hay/concentrate diet there was little net uptake or output of glucose by the gut. However, there was consistent production of glucose by the liver, amounting to a maximum, in this study, of about 11 mol/24 h, assuming constant glucose production throughout the 24 h day. The rate of carbon dioxide appearance in the portal vein was about twice that of oxygen uptake by the gut. The liver used oxygen, and produced carbon dioxide, at nearly equal rates. The uptake of glucogenic substrates by the liver accounted adequately for the observed rates of hepatic gluconeogenesis.

In one of the lactating cows it was observed that there was a net production of acetate by the liver that amounted to half the net absorption of acetate from the gut (ethyl alcohol was not the precursor of this acetate) and that (glutamine + asparagine) and serine had the highest rates of appearance in the portal vein and the highest rates of uptake by the liver.

This paper presents an iterative analysis of incomplete variety × environment tables. The analysis estimates potential differences in the sensitivity of varieties to environment effect. It is noted that the technique allows unequal weighting of data, and the special case of a complete table is discussed.

A 2-year study conducted in Salinas, California in 1989–91 showed that soil nitrate (NO3–N) concentrations were reduced by cover crops during a short winter fallow period and that this practice can be compatible with year-round vegetable crop production schedules by planting and incorporating cover crops directly on the beds into which the lettuce crop will be direct seeded in the early spring. Cover crops grown the first year were oilseed radish (Raphanus sativus cv. Renova), white senf mustard (Brassica hirta cv. Martigena), white mustard (Brassica alba), Phacelia (Phacelia tanacetifolia cv. Phaci), rye (Secale cereale cv. Merced) and annual ryegrass (Lolium multiflorum). Only phacelia and Merced rye were included in the second year. In both years, all of the cover crops depleted soil NO3-N and soil moisture relative to the fallow control. Estimates of cover crop root length, based on core sampling to 60 cm soil depth, averaged 18800 m/m2 after 17 weeks of growth the first year and 12500 m/m2 after 13 weeks of growth the second year. Above-ground dry matter production averaged 449 g/m2 (12·8 g N/m2) the first year and 161 g/m2 (61 g N/m2) during a shorter growing period and under the more adverse growing conditions of the second year. Following cover crop incorporation with a rotary tiller, soil ammonium (NH4-N), N03-N and net mineralizable N (anaerobic incubation) peaked after c. 1 week, then gradually declined for 1 month. Cover-cropped plots sustained higher net mineralizable N levels than the fallow control after incorporation. Nitrate concentrations after spring rains were lower in soils left fallow during winter. The subsequent lettuce crop was not affected by cover crop treatment.

This paper gives measurements of soil physical conditions and root growth made in the experiment described in the previous paper. The effect of methods of tillage on soil properties (strength, bulk density, nutrient distribution and fauna) and the effects on root development and the absorption of nutrients from different depths in the soil were investigated. The procedures used for these measurements are described.

Greater soil compaction occurred in all years after direct drilling. The growth of seminal roots of young plants was reduced by direct drilling in each year but only in the first year were there significant differences in root development between treatments at later stages of growth. Similarly, in each year early shoot growth was reduced by direct drilling but, with the exception of the first year, the plants were subsequently able to compensate adequately. Direct drilling resulted in more earthworms being present in the soil, and caused the surface soil to be more friable and contain a higher concentration of available phosphorus and potassium.

Five groups of four 8-week-old Blackface lambs were used to compare the effects of dietary deficiencies of calcium and/or phosphorus: four were given for 16 weeks a semi-purified diet low in Ca (0·07 %) and P (0·13 %), either unsupplemented (LCaLP) or supplemented with 0·3 % Ca (NCaLP), 0·3 % P (LCaNP) or both (NCaNP), and the remaining group was slaughtered initially.

The only clinical abnormality observed was twisting of the forelegs in group LCaLP. Food intake was depressed by 26 % in LCaNP group, by 41·5 % in NCaLP group but was largely unaffected in group LCaLP. Apparent D.M. digestibility was lower for group NCaLP (57·7 %) than for other groups (61·2 %). Differences in live weight and body fat reflected the differences in food intake between treatments but the weights of fat-free body components were lowest in the groups given low P diets.

The LCaNP diet decreased plasma Ca and increased plasma P but the NCaLP diet had the opposite effects. The LCaLP diet had no effect on plasma Ca and decreased plasma P less than the NCaLP diot.

The three mineral deficient diets caused equally marked decreases in Ca and P retention but did not induce negative balances; they also impaired the quality of bone in the tibia and lumbar vertebra, by reducing both the amount of bone matrix and the degree to which it was mineralized, and produced histological lesions of rickets and osteoporosis. Diets low in P caused a marked fall in Mg content of the skeleton.

Urolithiasis was common in lambs given diets adequate in P.

There is a strong correlation between the digestibility of the organic matter and the percentage crude fibre, percentage lignin, and percentage cellulose plus lignin in the foodstuffs examined.

There is evidence that the holocellulose and xylan in grasses are different from those in legumes in the extent to which they are digested. It is suggested that this is due mainly to the xylans or hemicellulose fraction in the forages, and may be a reflexion of a different molecular structure for the xylans in either group.

Within each group of plants both the holocellulose and xylan percentages are strongly correlated to the percentage digestible organic matter.

Excessive heating of hay led to a marked rise in the percentage lignin. This is probably due to the xylans becoming horny and insoluble, therefore being determined as lignin. This also offers an explanation for the decrease in digestibility of the organic matter.

Although it has been generally recognized that the difference in yield potential amongst wheat cultivars released in different eras is related to differences in their reproductive sink strength, there have been few investigations about changes in source–sink ratios as a consequence of wheat breeding. In the present study, two field experiments, in which plots were fertilized and irrigated and lodging and diseases were prevented, were carried out with seven cultivars (including a commercial hybrid) representing different periods of plant breeding in Argentina from 1920 to 1990. The cultivars were defoliated during post-anthesis to analyse the response of grain weight at particular positions within the spike (which have intrinsic differences in potential size).

Individual grain weight was virtually unaffected by defoliation in the old cultivars, but modern cultivars exhibited a significant reduction in individual grain weight for several positions within the spike, although this reduction was small (c. 15%) and many grains were unaffected. In addition, no relationship was found between individual grain weight in the controls and its reduction due to defoliation.

We concluded that if the source–sink ratio is further reduced, the grain yield of modern wheats will be simultaneously limited by the source and the sink. Future breeding should therefore attempt to improve simultaneously both sink and source strengths.

1. Data are presented indicating that both the total yield of potatoes and the proportions of the yield in size grades were a function (independent of set size) of the number of main stems per unit area for the maincrop varieties Majestic and King Edward.

Volatilization of ammonia (NH3) from slurry applied in the field is considered a risk to the environment and reduces the fertilizer value of the slurry. To reduce volatilization a better understanding of the slurry–soil interaction is needed. Therefore, the present study focuses on measuring NH3 volatilization as affected by differences in infiltration. Livestock slurries with different dry matter (DM) composition and viscosity were included in the experiments by using untreated cattle and pig slurry, pig slurry anaerobically digested in a biogas plant and pig slurry anaerobically digested and physically separated. NH3 volatilization was measured using dynamic chambers and related to infiltration of the livestock slurries in the soil by measuring chloride (Cl−) and Total Ammoniacal Nitrogen (TAN=ammonium (NH4+)+NH3) concentrations in soil at different depths from 0·5 to 6·0 cm from the soil surface. The slurries were applied to sandy and sandy-loam soils packed in boxes within the chambers. There were no significant differences in relative volatilization of NH3 from untreated cattle and pig slurries, but anaerobic digestion of pig slurry increased volatilization due to increases in pH. However, physical separation of the digested slurry reduced the volatilization compared with untreated slurry, due to increased infiltration. In general, the volatilization decreased significantly with increased infiltration. The present study shows that NH3 volatilization from applied slurry can be related to infiltration and that infiltration is related to slurry composition (i.e. DM content and particle size distribution) and soil water content. The infiltration of liquid (measured by Cl− infiltration) was affected by soil water potential, therefore, Cl− infiltrated deeper into the sandy loam soil than the sandy soil at similar gravimetric soil water values. Dry matter (DM) and large particles (>1 mm) of the slurry reduced infiltration of liquid. A high proportion of small particles (<0·025 mm) facilitated infiltration of TAN.

Digestibility trials were carried out using wether sheep, to determine the organicmatter digestibility of several forages. Acid detergent fibre (ADF) was isolated from samples of feed and faeces, incubated in buffered cellulase solution, and the ash-free residue remaining (IADF) was used as an internal marker to estimate the organicmatter digestibility (OMD) of the feeds. Estimates of the OMD value of the samples were also made using the standard in vitro digestibility technique.

IADF had reached a constant value after incubation for 4–5·5 days and predicted OMD more precisely than the in vitro digestibility technique.

It is concluded that IADF is a suitable internal marker and predicts OMD well. However, more work is required to test this technique over a wider range of herbage species and digestibilities.