Fourteen young wether sheep were fed freshly cut Lotus pedunculatus as a sole diet to examine the effects of condensed tannins (CT; 55 g/kg lotus DM) on nitrogenous aspects of digestion. The experiment was carried out indoors at Palmerston North, New Zealand over 32 days with one group of sheep receiving an intraruminal infusion of polyethylene glycol (PEG; 100 g/day) to preferentially bind CT (PEG group) so that the lotus was essentially 'CT-free'. The other sheep, not given PEG, were termed the 'Tannin' group. The principal effects of CT were to increase the flow of feed nitrogen (N) to the abomasum despite a 12% reduction in DM intake of the Tannin sheep. Rumen microbial N turnover rate was slower in Tannin animals than in those receiving PEG (1.86 v. 2.63/day) but microbial N flux to the abomasum was similar in both treatments. The proportion of N intake disappearing from the rumen was lower in Tannin (0.13) than in PEG sheep (0.26) and the N digestibility was 0.67 and 0.81 for the respective treatments (P < 0.001). The beneficial effects of CT in reducing rumen degradation of feed protein were negated in part by a reduction in fractional absorption of amino acids (AA) from the small intestine. Fractional absorption of essential AA was 0-66 in Tannin and 0.79 in PEG sheep; values for non-essential AA were 0.59 in Tannin and 0.73 in PEG groups. Amino acid concentrations in blood were similar for both groups, but Tannin sheep had lower plasma urea concentrations, a more rapid plasma urea turnover rate and a higher irreversible loss than those receiving PEG. Growth hormone concentrations in plasma were similar for both treatments.
The effects of root and shoot characteristics on the lodging resistance of four cultivars of winter wheat were investigated by combining results from a field trial (set up at Manchester University's Experimental Grounds, Jodrell Bank, in mid-September 1991) with morphological and mechanical measurements on their stems and anchorage systems. Cultivars showed contrasting lodging resistance: Widgeon was most susceptible, followed by Galahad, Riband and Hereward which, alone. did not lodge. Lodging resistance was not related to the strength and stiffness of the stems, which were usually adequate to withstand the forces to which they were subjected. Most plants instead failed in their root system which rotated through the soil. Resistance was associated with short and light stems (and hence on the force applied to the plants by wind and gravity) and with high values of the anchorage strength of the root system (and hence on the force resisting logding). Lodging occurred during grain filling when the ears were heaviest and when the soil was wet. The anchorage strength of a plant depended on two characteristics of the root system: the bending strength and the angle of spread of the basal coronal roots. Plants with stronger, more widely spread coronal roots produced larger soil cones during anchorage failure and resisted larger forces. Future breeding for lodging resistance, therefore, should continue to select for plants with shorter stems and with stiffer, more widely spread, coronal roots.
Lotus pedunculatus was grown under high fertility conditions and its nutritive value was determined in a feeding trial with sheep at Palmerston North, New Zealand in 1989. The condensed tannins (CT) accounted for 5.5% of lotus dry matter (DM) and its effect on digestion was evaluated by giving an intraruminal infusion of polyethylene glycol (PEG) to six of the sheep (PEG group). PEG preferentially binds with CT so that the lotus becomes essentially CT-free. The experiment was carried out with 14 sheep (six PEG and eight 'Tannin') held in metabolism crates indoors and given freshly cut lotus hourly, for 32 days. This paper presents data relating to carbohydrate and mineral digestion, together with aspects of rumen function. Digestibility of lotus DM was 68%, and the digestibility of fibre was not affected by CT. Infusion of PEG increased rumen concentrations of NH3 and volatile fatty acids (P < 0.001) but effects on molar ratios of VFA were inconsistent with time. CT reduced rumen degradation and absorption of sulphur and increased net absorption of both phosphorus and zinc, but other effects on mineral digestion were small. Although the lotus was offered at c. 90% of ad libitum, intakes of the tannin sheep began to decline after c. 15 days of feeding and were c. 12% lower than those of the PEG sheep at the end of the trial (P < 0.05). At slaughter, rumen pool sizes were similar for the two treatments but the Tannin sheep had a lower fractional outflow rate, which suggests a slower rate of digestion in the rumen. Growth rate and wool production were similar for sheep on both treatments. It is concluded that the CT in Lotus pedunculatus grown under high fertility conditions had little effect on fibre and mineral digestion but the depression in DM intake reduced its nutritive value for sheep.
The largest yields of wheat and potatoes came from the combination of longer ley plus optimum fertilizer N but yields of winter beans were decreased where N had been given to the previous crops. Without fertilizer N, two year old leys significantly increased yields compared to one year leys and the effect of longer leys was small except for the first wheat, when grain yields were large and plateaued after the three year ley. Exponential response curves were fitted to the wheat yields and an exponential plus linear trend to the potato yields after each of the leys. Maximum yields and maximum economic yields and their associated N dressings were then estimated. Maximum economic yields of wheat in 1987 ranged from 8.11 to 9.14 t/ha grain and the fertilizer N needed declined from 174 kg/ha after the one year ley to 48 kg/ha after the six year ley. For potatoes in 1988, yields ranged from 63 to 71 t/ha tubers but the N required (137-150 kg/ha) varied little with ley age. For winter wheat, in 1989 yields ranged from only 5.51 to 6.99 t/ha grain, because of drought but, as with the potatoes, the N required (203-218 kg/ha) varied little. For each crop the six individual N response curves could be shifted to bring them into coincidence, and the benefits of the ley estimated in terms of a quantity of fertilizer N applied in spring (horizontal shift) and effects other than spring N (vertical shift). The spring N effects relative to the one year ley varied with ley age; for the first wheat the range was from 6 to 126 kg N/ha for the two to six year leys respectively. Spring N effects were negligible, however, for potatoes (average 6 kg/ha) and also for wheat in the third year (.6 kg/ha). Benefits other than those which could be ascribed to spring-N increased yield of the first wheat, on average, by 0.94 t/ha grain for the two to five year leys; for potatoes they ranged from 3.5 to 8.1 t/ha tubers for the three to six year leys; for the third crop wheat they ranged from 0.86 to 1.49 t/ha grain for the three to six year leys. On average the first wheat recovered only 34% of the applied fertilizer N whilst potatoes and the following wheat recovered 55 and 56% respectively. There was a benefit from the longer leys which affected the efficiency with which fertilizer N was used. Increasing ley age up to five years increased total soil carbon by a maximum of 0.17% C; 18% of the carbon content of the soil in the one year ley plots. This small increase in soil organic matter provided up to 230 kg/ha mineral N in the first autumn after ploughing. Between 17 October 1986 and 27 April 1987 the average loss of NO3-N from soils following three to six year leys was equivalent to 202 kg N/ha, whilst the average uptake of N by 11 May in the above-ground wheat was only 88 kg/ha; the net loss was 114 kg N/ha. A computer simulation, which included mineralization of organic N during this period together with N uptake and nitrate leaching losses, computed a loss of 250 kg N/ha following the six year ley, and this would have given 400 mg NO3/l in the 275 mm through drainage that winter.
Yields from five of the plots on the Park Grass Continuous Hay experiment at Rothamsted, started in 1856, were examined to see if any long-term trends could be detected over the last 100 years. Three of the plots examined are unfertilized; two receive inorganic nutrients every year; all are harvested twice a year. In 1959 the harvesting procedure was changed: yields for the periods before and after this change were examined separately and together. On none of the three unfertilized plots was the slope of the regression of total yield (i.e. first and second cuts combined) on time significantly (P < 0.05) different from zero in either the 1891-1958 or 1960-1992 periods. On both the fertilized plots, there were significant declines in yield with time over the 1960-92 period, assuming that the effects of autocorrelation are sufficiently small to be ignored; there were no consistent changes between 1891 and 1958. There were some significant trends on the five plots when the two cuts were considered separately. A linear regression model was fitted to the data in an attempt to separate the effects of meteorological variables (rainfall and sunshine hours over selected parts of the year) on total yield from possible long-term effects brought about, for example, by the increasing concentration of CO2 in the atmosphere. On four of the five plots this model accounted for between 12 and 21 % of the yield variance in the pre- 1 959 period and between 45 and 63 % after 1960. On the fifth plot, which received the highest level of N, the model accounted for 29 % of the variance in the first period but only for 16 % in the second period. When a linear trend with time was included in the model, this was not significant on any of the plots over the entire 1891-1992 period, although some significant trends appeared when the two periods were considered separately. The model was also fitted with the atmospheric CO2 concentration in place of the linear trend with time: again there were no consistent trends. Neither changes in the concentration of CO2 in the atmosphere over the last century nor increasing inputs of combined N in rainfall or in dry deposition have had any detectable effects on yield in these plots.
In the first two of four experiments, sheep were fed, ad libitum, sorghum stover supplemented with graded levels of foliage of the shrub leucaena (Leucaena leucocephala) or mulga (Acacia aneura), which provided between 0 and 0.34 or between 0 and 0.43 of the dietary dry matter (DM) respectively. A second treatment (with or without urea) was superimposed in a factorial design. The effect of treatments on liveweight (LW) was explainable by their effects on voluntary intake of apparently digestible organic matter (DOMI). DOMI was increased by mulga, largely due to an increase in the total voluntary intake of organic matter (OM). Leucaena increased DOMI by increasing the ration OM digestibility and, at low levels of inclusion, intake of the basal diet. Roughage intake was greatest when leucaena provided 0.15-0.20 of the dietary DM. Leucaena increased rumen ammonia, and whenever roughage intake was increased by urea, leucaena also increased it. In the third experiment, when diets were made isonitrogenous with urea, roughage intake was slightly greater when leucaena, rather than its ash or a mineral mixture, was supplemented. Total OM intake and DOMI were greatest when leucaena was fed. In the final experiment, sheep were fed one of ten treatments: three basal diets (two of sorghum stover and the third of native pasture hay) each supplemented with legumes (leucaena to the hay and one stover diet and cowpea straw to the second stover diet), ash of the respective legume and formaldehyde-treated casein. The tenth treatment was sorghum stover plus urea. For sorghum stover diets with leucaena-based or cowpea straw-based supplements, DOMI responded linearly to the non-urea nitrogen concentration of the diet. On the other hand, for native hay with leucaena-based supplements, the response of DOMI to non-urea N was negligible. It was noted that the native hay (predominantly Flinders grass, Iseilema vaginiflorum), contained lower concentrations of polyphenols than sorghum stover. It was concluded that browse foliage can increase the voluntary DOMI of sheep consuming low quality roughages by providing nitrogen and sometimes minerals and OM of greater digestibility. The slowly-degradable proteins in leucaena, cowpea straw or formaldehyde-treated casein are more effective with polyphenol-rich sorghum stover than with native hay of otherwise similar composition.
Field experiments with the South American grain crop, quinoa, were carried out at two sites in Denmark in 1988-90 in order to study the effects of varying the nitrogen fertilization rate, seed rate, row spacing, harvesting method and harvest date. Although there was a significant yield increase when the amount of nitrogen fertilizer was increased from 40 to 160 kg N/ha, quinoa seems to be well adapted to poor soils. Yield decreased by 24.1% when the nitrogen supply was reduced from 160 to 40 kg N/ha, while the yield decrease was 12.0 and 2.7% when the nitrogen supply was reduced to 80 and 120 kg/ha, respectively. A model expressing yield as a function of plant density, for three experiments analysed as one, showed an optimal plant density with respect to yield of 327 +/- 220 plants/m2. This plant density was the top point of the curve relating yield to plant density. However, the large standard deviation indicates that apparently a rather wide range of plant densities would provide similar yields. When the row spacing was varied, it was shown that plots with a row spacing of 50 cm, which were hoed, gave a higher yield than plots with 25 or 12.5 cm row spacing, which were unhoed. There was an overall increase in yield when changing from combined harvesting to swathing; however, when comparing the yields from the optimal harvest dates for the two methods, no yield differences could be detected. The optimal harvest date for swathing was found to be the stage when the inflorescences start to turn brown, whereas for combining, the optimal harvest date was the stage when most of the inflorescences are already brown.
A field experiment was conducted in Canterbury, New Zealand to investigate the effect of six leguminous and non-leguminous grain crops on soil N fertility over a 12 month period (March 1989 to March 1990). All crops had an overall negative N balance during their growing season. A greater amount of soil N was removed by barley, rape and lupins (104-119 kg N/ha) than by field beans, field peas or lentils (50-74 kg N/ha). Net N mineralization was measured in all treatments between residue incorporation and the start of winter. With the exception of the lupins, accumulation of mineral N in the soil profile before the start of winter drainage was greater following leguminous (mean 124 kg N/ha) than non-leguminous crops (mean 80 kg N/ha). Cumulative apparent leaching losses over the autumn/winter were largely a reflection of the mineral N content of the profile before the start of drainage. Excluding lupins, leaching losses declined in the order fallow > legumes > non-legumes (110 > 72 > 37 kg N/ha respectively). The anomalous results for the lupins were attributed to the incorporation of a large amount of woody residues after harvest which may well have resulted in extensive net N mineralization occurring later in the autumn. Over a 12 month period, all treatments showed a decline in N fertility (110-160 kg N/ha), although compared with barley, the total loss of soil N was 10-40 kg N/ha less following leguminous crops. Growth of the following spring wheat test crop was affected by the preceding crop. Grain yield, grain N yield and total N yield were significantly related to the mineral N content of the soil at the end of leaching, and to a measure of net N mineralization during the growing season of the test crop.
In three separate experiments, groups of four, three and six mature, rumen-cannulated Simmental cows were fed diets designed to supply different quantities of energy (E) and nitrogen (N) to the rumen microbes. Experiment 1 (straw plus concentrate plus urea) had balanced E and N supplies; Expt 2 (hay and four levels of soyabean meal) had different sub-optimum N levels at the same intake as Expt 1; and Expt 3 (hay plus maize plus two levels of urea) reproduced the N shortage in Expt 2 at a higher level of intake. The amount of total N excreted in the urine (TUN) was 574 mg/kg LW0.75 in Expt 1 and 42.0 mg/kg LW0.75 of this N was excreted as total purine nitrogen (TPN). In Expt 2, TUN increased significantly (P < 0.05) with increasing soyabean levels; TPN also increased, reaching the level observed in Expt 1 when soyabean meal supplementation was highest. In Expt 3, TUN and TPN increased with increasing dietary urea concentrations; TUN and TPN were always higher than in Expts 1 and 2. Estimated microbial nitrogen supply (EMNS, based on TPN) was always considerably lower than estimates based on fermentable non-protein OM and crude protein (EMNR-EN) or an assumed yield of microbial N per kg OM apparently digested in the rumen (EMNR-OM). Regression analyses of EMNS on EMNR-EN, EMNR-OM or OM intake had moderate r2 values (0.76, 0.65 and 0.62 respectively) but the constant terms were significantly different from zero. The regressions of EMNR-EN and EMNR-OM on TPN gave angular coefficients of 15.81 and 11.47 respectively. The correlation between rumen liquid parameters (total count, bacterial DM, ATP and nitrogen) and OM intake, EMNS or EMNR increased with sampling time (from 09.00 to 16.00 h). The EMNR-OM produced correlation coefficients similar to those obtained with OM intake; these correlations were numerically higher than those obtained with EMNS or EMNR-EN.
Methods of adjustment for two-dimensional spatial heterogeneity of grain yield were investigated for 224 UK cereal trials. The methods used row and column 'block' analysis of plot yields and neighbour analysis based on first differences of plot yields. In 36 % of trial analyses for block models and 30 % for neighbour models the average variance of variety differences was reduced by more than 10 % compared with the better of the one-dimensional row or column models. Compared with complete blocks, 2-D block analysis had a mean efficiency of 153 % whereas the conventional 1-D block analysis (by rows) had a mean efficiency of 127 %. Similarly, 2-D neighbour analysis had a mean efficiency of 159 % whereas the 1-D analysis had a mean efficiency of 137 %. Recently, general statistical methods have been developed for two-dimensional design and analysis; their wider use should lead to major gains in the precision of variety trials.
To develop an effective breeding programme for rainfed production of the common bean (Phaseolus vulgaris L.), the inheritance of seed yield under such conditions should be understood, preferably considering the effects of environment to account for site or season specificity. Thus, heritability, expected and realized gain from selection, and combining ability were evaluated for a nine-parent diallel of common bean without reciprocals but including parents, at two locations each in Mexico and Colombia, using the F2 and F3 and F3 population bulks. Heritability estimated from regressions of F3 on F2 ranged from 0.09 +/- 0.18 (S.E.) to 0.75 +/- 0.25 for seed yield, from 0.26 +/- 0.09 to 0.34 +/- 0.09 for days to maturity and from 0.57 +/- 0.04 to 0.80 + 0.04 for 100-seed weight. Expected gain from selection in the F2 was estimated as a percentage of the population mean, selecting the upper 20% of the populations. Expected gain in seed yield ranged from 1.8 to 8.4 % in Mexico and from 6.5 to 28.1 % in Colombia. Realized gains in seed yield in the F3 were 0.4-7.4% in Mexico and 2.9-15.7% in Colombia. Realized gain values for days to maturity were 13.4 %. General combining ability (GCA) mean squares (estimated using Griffing's Method 2, Model 1) were significant (P < 0.01) and larger than those for specific combining ability (SCA) for all traits at all locations. The parents from the Mexican highlands tended to have a positive GCA effect for yield in Mexico but negative values in Colombia, whereas parents adapted to mid-elevation tropical environments showed the opposite tendency. However, all significant GCA values of breeding line V8025 were positive in both countries.
A series of experiments was conducted at Palmerston North, New Zealand, during 1988-91 to compare the efficiency of chewing during eating and rumination, rumen fractional outflow rate (FOR), voluntary organic matter intake, liveweight gain and wool production in sheep fed either low (LS) or high (HS) leaf shear breaking load perennial ryegrass (PRG). The LS ryegrass had a 13% lower mean leaf shear breaking load and ingestion rates tended to be higher than for HS PRG, but no consistent significant treatment differences were observed in rate of particle breakdown, rumen FOR, voluntary intake or animal performance. It was concluded that selection for reduced leaf shear breaking load per se did not improve feeding value. The total shear load required to reduce a unit dry weight of PRG leaf to < 1 mm particles (index of masticatory load; IML) differed by only 3% between LS and HS PRG in this study, due to higher leaf length: dry weight ratios for LS PRG. It is therefore suggested that IML, which takes into account both leaf shear breaking load and associated changes in leaf morphology may be a better criterion for selection than leaf shear breaking load alone in breeding programmes to improve the feeding value of perennial ryegrass.