Conniffe, Browne & Walshe (1970) proposed a form of experimental design and statistical analysis for grazing experiments. The original paper did not include any example of the analysis on real data. This note presents such an example and makes some comments on the statistical validity of the method of analysis.

Aqueous ammonia supplying 125, 250, 375 or 500 kg N/ha was injected in spring (in bands 10–13 cm deep and 30 cm apart) into old permanent pasture stocked with cattle. Yields from it were compared with those from ‘Nitro-Chalk’ supplying the same total quantities of N, but broadcast in six equal amounts during the growing season. The tests were made first in 1969 and repeated on the same plots in 1970 and in 1971.

Yields of herbage were measured by placing cages (0·9144 m square) on different parts of each plot during six grazing periods of an 8-month growing season (1 March to 30 October). The cages protected this grass from cattle, otherwise grazing unrestrictedly.

Aqueous ammonia produced slightly more dry matter during the first three periods (1 March to 30 June) and ‘Nitro-Chalk’ slightly more during the last three (1 July to 30 October). Total yields from the two sorts of N were similar.

Percentage N in dry herbage was larger with aqueous ammonia than with ‘Nitro- Chalk’ during the first three periods, the same with both fertilizers during the fourth, but larger with ‘Nitro-Chalk’ during the fifth and sixth periods.

Without N the pasture contained 36% of wild white clover during the first three grazing periods and 28% during the last three. Giving 125 kg N/ha of either fertilizer decreased clover by more than half, and with more N the pasture contained less than 5% of clover.

The conventional method for the determination of the organic matter content of diets and faeces is by ashing the sample at 550 °C (A.O.A.C, 1965)

Organic matter (O.M.) = dry matter (D.M.)–ash.

If the sample contains calcium carbonate, then some of this carbonate will be converted to oxide (Vogel, 1951) and the weight of carbon dioxide evolved will be calculated as organic matter. The amount of carbonate converted will be dependent upon the temperature at which the sample is ashed and the duration of the ashing process. We have found (Ørskov, Hovell & Allen, 1966; Hovell & Greenhalgh, 1972) that when calcium salts of volatile fatty acids are included in diets given to sheep, most of the calcium is excreted in the faeces as carbonate, and since apparent digestibility is the difference between the amounts of nutrient ingested and excreted, the estimation of the apparent digestibility of organic matter will be in error if no correction is made for the high calcium carbonate content of the faeces. For example, a diet which contained 9·2% of calcium acetate had a true organic matterapparent digestibility of 86·8%. Had no correction been made this would have been estimated as 84·9%.

In a previous publication (Edwards & Duthie, 1971) the metabolizable energy values for broiler chicks of 11 samples of winter-sown Throws M. S. field beans from the 1968 harvest were reported. The samples had been grown at different locations in England which represented a variety of soil types. The mean ‘classical’ and nitrogen-corrected metabolizable energy values were 2–40 ± 0–09 kcal/g and 2–26 ±0-11 kcal/g respectively, with as much as 27 % difference between the highest and lowest individual values.

In 14 experiments made from 1968 to 1970 yields of, percentages of N in and amounts of N removed by the grain were compared: (1) when N was injected, either as aqueous ammonia (with or without a combine-drilled ‘starter’ dose of N) or as aqueous urea, or when broadcast as ammonium nitrate (‘Nitro-Chalk 21’) and: (2) when comparable liquid (14–6–8) and granular (20–10–10) NPK compound fertilizers were applied, either over the seed bed (sprayed or broadcast), or combine-drilled. All were applied to give 63 or 126kgN/ha.

Barley yields were increased significantly more by combine-drilled than by broadcast PK (0–20–20) fertilizer, especially when only 32 kg P2O5 and K2O/ha was given. N was better combine-drilled than broadcast when 63 kg/ha was given, but not with 126 kg/ha. Soil analyses suggested a limiting value for P.

Yields and N recoveries were largest when one-fifth of the N was combine-drilled (as 6–15–15) and the remainder injected as aqueous ammonia in bands 30 cm apart and 12 cm deep. Injecting all the N, either as aqueous ammonia or as urea, gave yields a little smaller than this, but still larger than from broadcasting ammonium nitrate.

The liquid NPK fertilizer gave smaller yields than the granular one in the two dry springs (1968 and 1969), but similar yields in the cool wet one (1970), both when applied over the seed bed and when combine-drilled. The smaller yields with the liquid fertilizer were associated with a severe check and loss of plant when it was combinedrilled (presumably caused by urea) and poorer growth after it was sprayed (presumably through loss of N to the air and greater dispersal of P in the soil). The single amount of each fertilizer increased yields more when combine-drilled than when broadcast, but not the double amount, which, especially as liquid, was safer when surface-applied. Effects of site and season upon mean yields were large.

Seven soil conditioners added to a sandy clay soil at Saxmundham did not benefit sugar-beet seedling emergence in four experiments in 3 years. In microplots at Broom's Barn free draining peat and sandy loam gave consistently more seedlings than limestone loam or flinty loam. In the laboratory, for each of three soil types, emergence was maximal only for a small soil moisture range and decreased rapidly when soils became drier or wetter. This suggests that conditioners which increase water-holding capacity should be tested on sandy loams rather than clay soils and that seed-bed preparation on heavier soils should seek to aerate the soil.

Two experiments have been performed to study the acclimatization of laying hens to cool or warm environmental temperature, using the comparative slaughter procedure to measure energy utilization. In the first experiment the energy balances over a 3-week period at either 10 or 35 °C were compared; in the second experiment a comparison was made of the energy balances over six consecutive weekly periods at similar cool and warm temperatures.

The first experiment confirmed that production could be maintained (88%) in the warm environment even though food intake was markedly reduced (95 and 63 g/day at 10 and 35 °C respectively). In both environments a loss of body weight indicated, that energy intake was insufficient to meet demands for at least part of the period.

During the first week of the second experiment there was a small loss of body weight in the cool environment and food consumption was slightly depressed. The results for energy intake, egg production and heat production suggest that acclimatization was complete after 1 week. In the warm environment egg production fell initially (62%) but returned to a high level (86%) during the second week. However, energy intake, body weight and heat production did not reach steady levels until the fourth week. Comparing the first 3 weeks with the subsequent 3 weeks the daily ME consumption was 137 and 161 kcal/kg¾ and the daily heat production was 126 and 116 kcal/kg¾. Similar, although less marked differences were observed in the cool environment. These results therefore emphasize the need to allow adequate time for acclimatization to the environment in studies of energy metabolism.