The availability to grass of the nitrogen in liquid anaerobically digested sludge (LDS) and liquid aerobic sludge (LAS) was investigated in a 2-year field trial. The mean availability of the nitrogen in the LDS over the 2 years was 44% on a freely drained sandy soil and 34% on a poorly drained clay soil. The corresponding values for the LAS were 56 and 44%. A greater inhibition or organic-matter decomposition by clay particles or a greater loss of nitrogen by either ammonia volatilization or denitrification were all possible reasons for the lower availability of the sludges on the clay soil. Investigation of the magnitude of gaseous losses of nitrogen from sludge-amended grassland under U.K. conditions is required. Current models of the availability of the nitrogen in liquid sludges may not be realistic if these losses are significant.

The heart rates and corresponding energy expenditure of adult Brahman cattle (Bos indicus) and water buffalo (Bubalus bubalis) were measured whilst they were standing, walking at speeds of up to 1 m/sec and pulling loads of up to 50 kg for periods of 1–2 h/day. Correlations of heart rate with energy expenditure showed a positive linear relationship within species although a distinct difference was exhibited between species. However, when heart rate and energy expenditure were expressed relative to their respective resting values (RHR and REE respectively), the results for all animals fitted the same line:

REE = 2·251 RHR – 0·954 (r = 0·93; n = 49).

More importantly, the relative heart rate and actual energy expenditure per unit metabolic body weight (EEW) for all animals fitted a common line:

EEW = 24·94 RHR – 16·25 (r = 0·91; n = 49),

where EEW is in watts/kg0·75 and RHR = heart rate of the working animal/heart rate at rest. This assessment of the energy expenditure from measurement of heart rate and live weight thus allows a prediction to be made of the energy requirements of working draught cattle under field conditions.

The growth of Huia white clover was followed in undisturbed and unsterilized soil cores containing a normal endomycorrhizal fungal population which had been inoculated with one of eight additional endomycorrhizal fungal isolates. Most of the endophytes significantly stimulated growth over filtrate controls at some stage in the experiment. Glomus mosseae, G. tenue and Gigaspora margarita produced large growth increments over a range of applied phosphorus levels. The inocula also contained a filtrable agent that was capable of reducing the growth of white clover.

Four field experiments were established to gauge the effect of inoculating white clover with selected strains of vesicular-arbuscular mycorrhizal (VAM) fungi. The four sites chosen ranged in fertility from undeveloped, phosphorus-impoverished tussock grassland to high fertility alluvial flats. As far as practicable conventional agronomic practices were followed prior to and during sowing. The soils were otherwise untreated and contained the normal complement of indigenous VAM fungi. Infested soil pellets were used to introduce the fungi into the soils as this was considered more appropriate to pastoral farming than for example transplanting infected seedlings.

Initially the introduced fungi tended to have little or no effect on dry-matter yields but by the end of the first season there were significant responses to Gigaspora margarita, Glomus mosseae, Glomus macrocarpum or a mixed inoculum of Glomus pallidum and Glomus tenue. In the second season, dry-matter yields were increased on the two tussock grassland sites by up to 760 kg D.M./ha (ca. 30%), 825 kg D.M./ha on the moderately fertile site (14%) and 640 kg D.M./ha (5%) on the high fertility site. The growth responses tended to decrease with time probably owing to the spread of fungi from the inoculated to the control plots though growth responses were still present at the end of the 3rd year on two of the sites. Within each experiment the application of up to 50 kg P/ha per year did not reduce the size of the responses to inoculation. This and herbage chemical analyses suggested that a more efficient use of phosphatic fertilizers may have been only part of the reason for the responses to inoculation.

Three American crisp lettuce varieties Ithaca, Pennlake and Saladin, formerly called Salinas, were sown on three occasions between April and July in 1980 and 1981 and on six occasions in 1982 between March and July. The rate of emergence of all three varieties increased with mean soil temperature at seed depth. The number of leaves was linearly related to air temperature measured on an accumulated day-degree scale > 0 °C from emergence. Pennlake had the highest rate of leaf production and Saladin the lowest rate. The relative growth rate of Ithaca increased with later sowing, while that of Pennlake declined. The time of maturity of one variety relative to another changed with sowing date but in all three varieties a quadratic curve relating the time of maturity to the time of sowing accounted for a high proportion of the variance in the time of maturity. When the times of sowing and maturity were both expressed on a day-degree scale > 0 °C a linear relationship accounted for more than 98% of the variance in time of maturity. These data provide the basis for planning a continuity programme. Within a variety there was considerable variation in mean head weight between sowings in the same year and different responses of head weight to sowing date from year to year. Using data from all 12 sowings, there was shown to be a significant association between head weight and the mean temperature up to 42 days from emergence but there was no association with radiation. Low mean temperatures (< 12 °C) were associated with lower head weights of Ithaca but higher head weights of Saladin. The opposite was true for mean temperatures greater than 16 °C. The reasons for this are discussed.

A variety of chemical reagents and treatment methods have been tested for their potential to enhance the digestibility of crop residues. The most universally used chemicals for animal experimentation in residue treatment are sodium or ammonium hydroxide (Chandra & Jackson, 1970; Koers, Prokop & Klopfenstein, 1972; Klopfenstein, 1978; Arndt & Richardson, 1982). These chemical treatments usually improve digestibility of roughages by solubilizing hemicellulose, and increasing the extent and rate of cellulose and hemicellulose digestion (Klopfenstein, 1978). Delignification is not usually considered to be an important aspect of chemical treatment (Klopfenstein et al. 1972), and increases in digestion are usually attributed primarily to breaking of bonds between lignin and carbohydrates rather than lignin removal. The aromatic nuclei of the lignin molecule are quite susceptible to oxidative attack (Sarkenen & Ludwig, 1971), and crop residues may be significantly delignified by oxidative chemical reagents (Sullivan & Hershberger, 1959; Sherrod et al. 1978; Ben-Ghedalia, Shefet & Miron, 1980). Ozonation is a chemical treatment method which is known to oxidize lignin and disrupt the lignocellulose complex. Several researchers have successfully applied the delignifying capability of ozone to improve the in vitro digestibility of roughages (Weakley & Owens, 1975; Ben-Ghedalia & Miron, 1981; Tock et al. 1982). Very little, however, is known of the actual in vivo feeding value of crop residues treated with ozone. These studies were conducted to determine the effect of ozone treatment on the feeding value of sorghum stover.