Large and consistent differences in growth rate of lettuce on different soils were recorded in two consecutive experiments in which lettuce cv. Avondefiance was grown for about 4 weeks in miniplots of 13 different soils. The miniplots were 20 cm in diameter and 20 cm deep and were buried flush with the soil surface at a single site. Each soil received the recommended amount of fertilizer and only seedlings emerging on a particular day were allowed to grow on. The relative performance of the different soils was very similar in each of the experiments with the plants in the best soil being 2·2–3·3 times heavier than those on the worst soil by the end of the experiments. The relative growth rates (RGR) of the plants were positively correlated with % P in the plants (accounting for 44–68% of the variation in RGR) and in turn with the availability of P in the soil. There was also a negative effect of soil organic matter on RGR, acting independently of % P, so that a multiple regression with % P and organic matter accounted for 65% of the variance of RGR in Expt 1 and 75% in Expt 2. Soil solution phosphorus appeared to be a useful measure for assessing phosphorus availability as plant growth was reduced only when concentrations fell below about 1 μg/ml.

Three experiments were conducted to determine the value of foliage from three tropical legume trees as low level protein supplements to napier grass diets for growing ‘Kacang’ goats. The average crude protein concentration in the napier grass was 12%.

Napier grass and foliage of the legume trees Gliricidia maculata, Leucaena leucocephala and Sesbania grandiflora were subjected to in situ microbial fermentation and subsequent treatment with acid-pepsin solution. The levels of N solubilized after 2 h incubation were 46 and 43% for napier grass and sesbania respectively, which were higher (P < 0·05) than those for gliricidia and leucaena (27%). Rates of protein disappearance between 2 and 24 h incubation in the rumen averaged 2·6%/h for the legumes and 1·0%/h for napier grass. The proportion of water-insoluble, rumendegradable protein from the legumes was larger (P < 0·05) than that from napier grass.

Napier grass intake by goats supplemented with gliricidia or leucaena at 15% of the dry-matter intake from napier grass was lower (P < 0·05) than that of controls receiving no legume supplement. Napier grass intake did not differ between controls and sesbania-supplemented goats. There was no difference among diets in total dry-matter intake, intake of cell wall constituents or digestibility. Average daily gain for control goats was – 1 g/day as compared with 21 g/day for supplemented goats.

The feeding of formaldehyde-treated soya-bean meal (F-SBM) as a supplement to either napier grass or napier grass–legume diets increased (P < 0·05) intake of dry matter and weight gain of goats. Napier grass intake of animals supplemented with only F-SBM was higher (P < 0·05) than that of control animals. The efficiency of N utilization from F-SBM was higher than that in the legumes, but replacement of legumes by F-SBM above 4% F-SBM feeding had no effect on weight gain or efficiency of utilization.

It was concluded that napier grass of 6–8 weeks' regrowth with 12% crude protein did not provide sufficient protein for growing goats owing to inefficient protein utilization. The increase in efficiency of protein utilization on supplemented diets is mainly associated with the larger proportion of water insoluble, rumen degradable protein and possibly acid-pepsin soluble protein in tropical tree legumes.

Two growth and two metabolism experiments were made in which a low gluoosinate rapeseed meal (var. Tower; TRSM) was compared with soya-bean meal (SBM) as the sole protein-rich material in simple diets containing barley and a vitamin and mineral supplement only.

In the first growth experiment 108 pigs were fed individually and restrictedly SBM and TRSM diets so that digestible energy (DE) and crude-protein intakes were similar. The DE used to promote a unit of growth or a unit of carcass weight was significantly less for the SBM, than for the TRSM, diet. In the second experiment 48 pigs were given, in groups of four, diets similar to those in Expt 1. There were no significant differences in growth rate or in serum thyroxine concentrations, but a significantly higher degree of thyroid hypertrophy was induced in pigs given the TRSM diet.

The two metabolism experiments compared the same diets used in the first growth experiment. Apparent digestibility of dry matter, nitrogen and gross energy, and retention of nitrogen relative to intake, were significantly greater for the SBM diet than for the two RSM diets. The addition of synthetic lysine to the TRSM diet significantly improved the apparent digestibility and retention of nitrogen. Pooled DE values (MJ/kg dry matter) calculated for SBM, TRSM and barley were 13·72 (S.E. 0·318), 13·97 (S.E. 0·211) and 14·01 (S.E. 0·080) respectively.

Herbage from a grass-white clover sward was dried in the field to the hay stage (≤ 0·33 g moisture/g dry matter) at three times of year in 2 years comparing, in each case, all combinations of two stages of maturity, two levels of applied nitrogen and two thicknesses of swath. Samples taken at intervals during drying were analysed for nitrogen, phosphorus, potassium, calcium, magnesium and sodium.

When there was little or no rain during drying, there was no change in the concentration of any of the six elements in the herbage dry matter between cutting and the hay stage, whatever the stage of maturity, level of N applied or swath thickness.

The concentrations of potassium and sodium in the crop were greatly reduced by rain in the later stages of drying, but were less affected by rain in the early and middle stages; the concentrations of calcium and magnesium appeared to be reduced by rain as readily in the middle as in the later stages; the concentrations of nitrogen and phosphorus were relatively little affected by rain, but seemed likely to be more at risk in the later stages. The extent of the reductions in the concentration of elements was not markedly affected by the stage of maturity or level of N applied. There were reductions in the thin but not in the thick swaths when rain fell during the early and middle stages of drying, probably partly or wholly because the herbage in the thin swaths was drier, with a higher proportion of dead cells, at that time than the herbage in the thick swaths. At least 70 kg K/ha was leached out of the crop in the thick swaths by rain in the late stages of drying.

Forty-one cows were used to determine calving intervals, intervals from calving to conception and pregnancy rates at 60–90 days postpartum for suckled and nonsuckled Bunaji cows. Twelve of the cows (six suckled and six non-suckled) were used to study the serum progesterone concentrations during the postpartum period. The mean intervals from calving to conception were 232·5 and 72·6 with calving intervals of 512·5 and 352·6 days for suckled and non-suckled cows, respectively. Pregnancy rates at 60–90 days postpartum were 21·1 and 72·7% for suckled and non-suckled animals, respectively. The overall mean calving interval and interval from calving to conception for all cows were 426·7 and 146·7 days, respectively, with a conception rate of 48·8%.

Based on serum content of progesterone and rectal palpation of ovaries, one of six suckled cows resumed ovarian activities within the first 90 days of calving with peak progesterone of 0·7 ng/ml. Four of six non-suckled cows resumed cyclic activities and conceived within the same period. Two of the four cows conceived at the first postpartum cycle and the remaining two conceived at the second cycle. The serum progesterone concentrations of the cows ranged from 0·1 to 6·9 ng/ml during the nonfertile cycle and 0·1 to 15 ng/ml at pregnancy. It is concluded that suckling interfered with ovarian activities and thus conception during the postpartum period, resulting in a prolonged calving interval.

A factorially designed growth and carcass dissection experiment was made in which a low glucosinolate rapeseed meal (cv. Tower, TRSM) was compared with soya-bean meal (SBM) as the sole protein supplement in simple diets, containing barley and a vitamin and mineral supplement (to give 18 mg copper/kg air-dry diet) only, which were fed individually on a restricted scale of feeding to 72 pigs. The diets were of similar digestible energy (DE) content and were formulated to contain in each kg of air-dry matter 150, 170 and 190 g crude protein. In each crude-protein level the total lysine content was similar. Also experiments using 35 pigs were made to determine the ileal apparent digestibilities of amino acids in barley-based diets containing SBM, the low glucosinolate rapeseed meals Erglu (ERSM) and TRSM and a high glucosinolate British rapeseed meal (BRSM) and either 20 mg or 200 mg copper/kg air-dry diet.

In the growth experiments there were no significant interactions for the variables considered. Pigs given TRSM diets, compared with those given SBM diets, had significantly poorer growth rates, conversion efficiencies and killing-out proportions but the proportions of lean and fat in carcasses and the backfat thicknesses (P2) were similar. There were no significant differences between protein levels in the killing-out proportions, the proportions of fat in carcasses and backfat thicknesses (P2) but pigs given diets containing 150 g, compared with 170 and 190 g, crude protein/kg air-dry diet had significantly lower growth rates and proportions of lean in the carcass and significantly poorer efficiencies of food conversion. The quantities of dietary crude protein used to produce units of live-weight gain, carcass weight and lean tissue increased progressively from the diets containing 150 to 170 to 190 g crude protein in each kg air-dry diet.

In the ileal digestibility studies the results indicated that amino acids were of a lower digestibility in the rapeseed meal diets than in those based on SBM and that the copper content of the diet may have been important in this context.

Blood samples were collected at 12-week intervals from 12 to 72 weeks from a total of 221 growing Friesian and Jersey calves and assayed for plasma concentrations of free fatty acids (FFA), ketones, glucose, calcium, phosphorus, magnesium, copper, albumin and globulin. Sixty-six of the animals could be allocated to genetically high and 73 to genetically low milk producing lines on the basis of being sired by the ‘best’ or ‘worst’ nationally available progeny tested sires. All animals were housed indoors and fed a complete pelleted diet ad libitum. There were no differences between genetically high and low milk production lines for any blood constituent and no useful indicators of genetic merit for milk production in later life. There were no differences between breeds for metabolites related to energy status (FFA, ketones, glucose). Friesians bad higher magnesium and lower mean copper concentrations than Jerseys and had higher phosphorus concentrations up to 36 weeks. Differences between breeds and ages in mineral concentrations were not related to breed differences in the discrepancy between observed intakes and predicted requirements of minerals. Concentrations of globulins were higher and of albumin lower in Jerseys than in Friesians at 12 and 24 weeks possibly owing to slightly higher disease incidence of Jerseys in early life. There were changes with age in concentrations of all constituents except FFA. There was evidence of genetic variation within breeds and lines for mean plasma concentrations of ketones, copper and globulin. There was no evidence for differences between females and castrates for any blood constituent.

A field experiment was conducted on acid soil of Kufri (Shimla) from 1980 to 1982 to study the effect of 30 t farmyard manure/ha (FYM) and 88 kg P + 160 kg K/ha (PK) on the response of potatoes to N fertilizer and on soil properties. There was a highly significant response of potato to N and the response was greater in the presence of PK than in the presence of FYM. The dose of N for maximum tuber yield with PK (39·9 t/ha) was 194 kg/ha, whereas for maximum yield with FYM (33·2 t/ha) it was 128 kg/ha. FYM met the P and K needs of potato when 100 kg N/ha was applied but not when 180 kg N/ha was applied. N fertilizer increased N concentration but decreased P and K concentration in leaves and tubers. The concentration of P and K was higher but that of N was lower with PK than with FYM. N fertilizer enhanced the uptake of P and K but its effect was not significant with FYM.

After 3 years of treatment FYM improved organic carbon, total N and NO3 status of the soil. N as calcium ammonium nitrate increased organic carbon in the presence of PK but decreased it in the presence of FYM. N fertilizer had little effect on total N, NO3 and available P content. N application depleted available K and the depletion was proportionate to the rate of N applied. The application of FYM and PK increased available P and K content of the soil and the increase was more with PK than with FYM.

In three factorial growth experiments and a metabolism experiment pigs of approximately 25 kg initial live weight were given on a restricted scale of feeding simple diets, based on barley, a vitamin and mineral supplement and either soya-bean meal (SBM) or a low glucosinolate rapeseed meal (cv. Tower; TRSM). Variations in these two basic diets were produced by adding different quantities of tannic acid, polyethylene glycol (PEG) and copper (Cu).

Diets based on soya-bean meal were used in the first experiment. There were no significant interactions. Tannic acid added at 3·75 and 7·50 g/kg air-dry matter was without significant effect on performance compared with no tannic acid addition, but PEG at 17 g/kg air-dry matter significantly improved growth rate compared with no PEG addition to the diet (P < 0·05). In the second experiment TRSM-based diets were used. There were no significant interactions and no significant effects on performance from adding 0, 8·5 and 17·0 g PEG/kg air-dry matter. Increasing Cu from 17 to 54 mg/kg air-dry diet significantly improved growth rate (P < 0·05). In the third experiment TRSM and SBM based diets, of similar digestible energy (DE), crude protein and lysine content, and containing either 19 or 202 mg Cu/kg air-dry matter, were used. Pigs were slaughtered at 87·5 kg live weight and hand joints dissected. Pigs given the TRSM diet containing 19 mg Cu/kg grew significantly more slowly than pigs given the three other diets between which there were no significant differences. There were no other significant interactions and no significant differences between Cu concentrations for the growth, carcass and efficiency of conversion results. Compared with TRSM diets, SBM diets at similar slaughter weights gave significantly greater carcass weights, killingout proportions and backfat thicknesses. Also the efficiencies with which dietary protein and DE were used to promote units of carcass growth were significantly better for the SBM diets, but there were no significant differences in the estimated weights of lean in carcasses.

In the metabolism experiments the effects of adding PEG to diets similar to those used in the growth experiments were examined. The apparent digestibilities of dry matter, gross energy and nitrogen and the nitrogen retentions were significantly greater for the SBM diets than for the TRSM diets. The addition of PEG to the SBM and TRSM diets significantly decreased the apparent digestibilities of dry matter and gross energy, and significantly increased the apparent digestibility of nitrogen in the SBM diet but not in the TRSM diet.

The emergence of seedlings from natural, germinating and selected uniformlygerminated onion seeds was compared in a range of changing patterns of soil moisture. The timing, spread and amount of seedling emergence from seeds in all three treatments were affected by the timing of water availability in the seed bed and these effects differed between treatments.

The rate of seedling emergence in all three treatments under non-limiting soil moisture conditions was correlated with mean temperature, but this relationship was obscured in irrigation treatments where water stress occurred. However, if the seed bed was moist at sowing irrespective of subsequent moisture stress the reciprocals of the time to the start, time to 50% and time to the end of seedling emergence from uniformly germinated seeds were correlated with mean temperature (r > 0·87, D.F. 27).

The results show that if the seed bed is irrigated prior to sowing and soil moisture is maintained during the first 3 days following sowing high levels of seedling emergence with both predictable timing and uniformity can be achieved by sowing uniformlygerminated seeds. Seedling emergence from natural and germinating seeds was much less predictable.

A representative soil sampling survey of arable and grassland fields in England and Wales between 1969 and 1983 is described.

The results show that of the rotationally cropped area 29% was below pH 6·5, and of the continuous grassland 46% was below pH 6·0. Levels of P and K were satisfactory except that 15% of grassland soils were low for P.

Data obtained by re-sampling the same fields at intervals of 5 years show that changes in the proportions of crops grown at different levels of pH and nutrients have been small. There has been some increase in the proportion of continuous grassland at lower pH, but the proportions of soils with low P and K have tended to decrease.

Drainage trials frequently lack any statistical evaluation of treatment differences, often because of practical difficulties in setting up randomized field experiments. Also, where detailed moisture measurements are carried out the usefulness of such data is small in relation to the workload involved. Procedures are described here which seek to rectify, in part, the above limitations.

Routine drain and surface condition data were analysed. Parallel regression analysis was used to compare drainage response patterns based on linear relationships between rainfall and peak drain flow. A point scoring system allowed treatment effects on surface conditions to be evaluated by x2 analysis.

Artificial drainage seeks to simulate naturally free-draining conditions. In line with this objective, soil moisture contents in the field, on a ‘Field Capacity Day’ (Stewart & Adams, 1968), were related to those at a standard (– 10 KPa) moisture tension typical of free-draining reference sites. Effectiveness of drainage performance was indicated by proximity of field and reference tension moisture contents.

Worked examples of each of the above procedures are provided. The procedures were found to be both sensitive and complementary. The value of the overall approach and its application under more normal agricultural conditions are discussed.

A series of drainage trials was set up to investigate various aspects of drainage design on former opencast coal mining land. The drainage problem was characterized. Subsoiling, subsoiling direction with respect to slope and drain spacing were assessed as factors affecting drainage performance. The persistence of subsoiling effectiveness was also monitored. Drainage performances were evaluated statistically (Scullion, Mohammed & Ramshaw, 1986).

Surface wetness was the predominant feature of drainage conditions on opencast land and the effectiveness of drainage treatments was limited to the control of this superficial water. Secondary drainage, in this case subsoiling, was found to be an essential feature of field drainage, reducing surface wetness and runoff. The effectiveness of subsoiling was dependent on there being sufficient gradient (4–5%) along channels for intercepted water to clear. For this reason, adoption of appropriate minimum reinstatement gradients and the arrangement of field drains to accommodate preferred directions of secondary treatments would assist drainage effectiveness.

There was a gradual deterioration in drainage performance as spacing increased. Spacings in the range 20–30 m appeared to offer a reasonable compromise between cost and benefit. The persistence of subsoiling treatments, which deteriorated markedly after 2–4 years, was not affected by drain spacing. Performance at the widest spacings tested was, however, generally poor regardless of time since subsoiling.

A basis for calculating design rates on individual sites and the implications for drainage theory of soil air-water interactions are briefly considered.

In a glasshouse study, the pattern of flower and pod production at the various flowering nodes of Phaseolus vulgaris (cv. 344) was mapped out. Soft X-radiation techniques were also used to study the development of retained and abscissed pods at the various nodes while varying levels of flower or pod removal were used to study the modification to pod development at each flowering node following organ removal.

The period of flower opening over the whole plant spanned an average of 12 days and 90% of the pods retained to maturity were formed from flowers opened within 4 days of anthesis. The terminal inflorescence produced most of the flowers on the plant (25%), but nodes 2 and 3 developed the bulk (50%) of the pods retained. Only 30% of the open flowers on the plant formed pods that were retained to maturity.

Pod elongation was initially very rapid in the pods to be retained, following successful fertilization, with the latter period of pod growth devoted almost entirely to seedfilling. A slow growth rate characterizes the development of abscission in Phaseolus pods and the number of seeds per pod is determined later in pod growth.

Flower or pod removal prolonged flowering and led to longer leaf retention and more branches on the main stem. The number of mature pods was lower on the treated plants and the more severe the removal the larger were these treatment effects. Plants compensated for fewer pods by having more seeds per pod but these were not enough to prevent significant depression of seed dry weight per plant by the most severe removals. Flower or pod removal led to a shift of emphasis in pod production by the plant from nodes 2 and 3 to other areas of the plant where natural wastage of flower and young pods is high.

Damage to barley grain cv. Golden Promise was induced in the laboratory by putting seed at 8·7, 14, 18, 22, 26 and 35% moisture content (MC) through a mechanical laboratory thresher for 10, 20 or 45 sec. The extent of visible external damage was greatest at 8·7 and 14% MC with reduced and similar levels of damage after handling at 18–35% MC. At moisture contents up to and including 26%, seeds could tolerate extensive mechanical damage with little effect on seed quality. Seed germination and seedling vigour were, however, reduced after handling at 35% MC despite similar levels of external damage to those seeds handled at 18, 22 and 26% MC. Samples of grain of cv. Triumph produced by whole-crop harvesting included mainly slightly damaged seeds with little effect of harvest moisture content, which ranged from 22·5 to 44%, on the incidence of damage. Seed germination and seedling vigour increased when seeds were harvested at progressively lower moisture contents, with the largest increase between 36% MC (56% germination, 6·1 vigour rating) and 29·5% MC (94% germination, 7·8 vigour rating). The seed quality of whole-crop harvested seed at 29% MC was similar to that of combined seed harvested at the same moisture content. It is suggested that 30 % is the maximum harvest moisture content at which commercially acceptable seed may be produced by the whole-crop harvesting method.

The persistence and productivity under grazing of seven accessions of Stylosanthes macrocephala, Zornia latifolia and Zornia brasiliensis in combination with Andropogon gayanus (cv. Planaltina) were investigated in small plots at two stocking rates on a low fertility, acid oxisol in the tropical savannah of the centre-west region of Brazil.

Two new accessions of S. macrocephala CIAT 2039 (CPAC 1033) and CIAT 2053 (CPAC 1034) were more productive and persistent than the control cultivar Pioneiro. After 4 years there were no differences in dry-matter yield between the two accessions. No anthracnose (Colletotrichum gloeosporioides) problems were noted in these accessions. Animals refused to graze Z. brasiliensis accessions at any time during the trial. Stocking rate effects became pronounced over time and legume contents were highest in the treatment grazed at 3·0 animals/ha. The advantages of the small-plot grazing method used in the experiment are discussed.

Flow rates of metabolites in an open-compartment model can be calculated from specific activity measurements taken at equilibrium during continuous infusion of an isotope. The within-animal variance gives an estimate of the precision of the flow rate.

The Jack-knife method of calculating within-animal variances is described. It was evaluated using simulated data, and shown to be superior to a simpler method, the Single Section method.

The increase in experimental accuracy caused by increasing the number of specific activity samples per animal depends on the ratio of between- to within-animal variance components (B/W). For three experiments with sheep, 23 of the 30 values B/W for the different flow rates ranged from 0·25 to 1·5. For this range between six and 12 samples per animal are needed.

A 4 x 4 latin-square design experiment was carried out to determine the effects of increasing nitrogen (N) intake by feeding diets containing increasing amounts of soyabean meal upon the digestion of organic matter (OM) and N by cattle equipped with rumen and duodenal cannulae. A basal diet (B) containing 600 g ground barley and 400 g grass silage/kg diet and three diets (BS1, BS2 and BS3) in which increasing amounts of the barley were replaced by soya-bean meal were fed. The mean daily intakes of OM and N when each diet was fed were 4·56, 4·55, 4·30 and 4·52 kg OM and 920, 114·7, 138·3 and 164·1 g N for diets B, BSl, BS2 and BS3 respectively.

Neither the amounts of OM entering the small intestine nor those voided in the faeces were altered by the diets fed. Thus the mean apparent OM digestibility for all the diets fed was 0·74 + 0·013 and the proportion of digestible OM intake apparently digested in the rumen was 0·77 + 0048.

Mean daily concentrations of ammonia N in the rumen were significantly (P < 0·001) increased from 38 mg N/l (diet B) to 129 mg N/l (diet BS3) as N intake increased.

The quantities of non-ammonia N and of amino acid N entering the small intestine were not significantly (P >0·05) increased as more soya-bean meal was added to the diet, although diet BSl supported the greatest flows of N to the small intestine. Thus as more soya-bean meal was added to the diet there were increasing net losses of nonammoniaN(P < 0·01) and amino acid N (P < 0·01) prior to the small intestine. Faecal N excretion was not increased (P > 0·05) as soya-bean meal intake increased and thus apparent N digestibility was significantly (P < 0·01) increased by increasing soyabean intake.

Both the quantities of microbial N entering the small intestine daily and the apparent efficiency of microbial N synthesis within the rumen were increased when diet BSl was fed in comparison with the basal diet (B) and then declined when diets BS2 and BS3 were fed; these increases were not significant. The quantities of feed N entering the small intestine daily were not significantly (P > 0·05) increased as soya-bean meal intake increased; thus apparent feed N degradability in the rumen was significantly (P < 0·01) increased as soya-bean meal intake increased. In contrast, the rates of disappearance of N from each of the components of the diets fed, when incubated in the rumens of the cattle in porous synthetic fibre-bags, were not increased (P > 0·05) as soya-bean meal intake increased.

Information on the total organic matter intake, concentrates supplied (C), live weight (LW), week of lactation (WL), milk yield (MY), herbage organic matter digestibility (HOMD), herbage mass, sward height (SHT) or herbage allowance (HAL) measured individually for 357 cows at one of three sites was assembled. Observed intake was compared with intakes predicted by existing intake equations and new prediction equations based on regression models or regression and least-squares constants were developed. Major factors affecting intake were MY, LW, WL, C and HAL or SHT. Although HOMD was correlated with intake, better predictions were obtained when HOMD was omitted. There were differences between sites possibly associated with differences in measurement techniques.

The predictive value of some existing equations and new equations were tested against independent sets of data. A simple equation (A) based on MY and LW (Ministry of Agriculture, Fisheries and Food, 1975) gave satisfactory average predictions but the mean square prediction error (MSPE) was high. The equations of Vadiveloo & Holmes (1979) adjusted for bias gave a relatively low MSPE. The preferred new equations for grazing cattle included MY, LW, WL, C and HAL or SHT, and their MSPE were similar to or lower than for indoor equations.

The discussion indicates that a simple equation (A) would give adequate predictions for farm planning. The more detailed equations illustrate the inter-relations of animal with sward conditions and concentrate allowances. Predicted intakes may deviate from actual intakes because of short-term changes in body reserves.

Inoculation of 3·0 t of fresh Azolla pinnata (Bangkok) per hectare 15 days before transplanting, 10 and 30 days after transplanting produced Azolla mats on the water surface 10, 12 and 15 days after inoculation, respectively. The Azolla growth and N2-fixation before transplanting were more than that after transplanting. Growing Azolla once before transplanting and twice after transplanting produced a total of 51·0–52·8 t fresh Azolla/ha, which fixed 92·8–96·0 kg nitrogen, whereas growing it once before transplanting plus once after transplanting and twice after transplanting produced 35·0–40·0 and 29·0–37·5 t fresh Azolla/h, and fixed 660·–72·4 and 52·5–66·1 kg N, respectively.

Application of Azolla increased the plant height, tillering, grain and straw yields of rice and also the fertility of the soil at harvest. Growing and incorporating Azolla once before transplanting and twice after transplanting of rice increased the grain and straw yields significantly more than applying 60 kg N/ha as urea and showed greater effect on soil fertility.

Growing Azolla before or after transplanting the rice in combination with 30 kg N/ha as urea and Azolla once before transplanting and once after transplanting without incorporation gave responses similar to that obtained by a divided application of 60 kg N/ha as urea. Growing and incorporating Azolla twice after transplanting showed slightly less response than growing it once before and once after transplanting and giving 60 kg N/ha as urea but slightly more than giving 45 kg N/ha as urea. The Azolla pinnata collected from Bangkok and Vietnam when used once before transplanting at equal biomass (15·0 t/ha fresh Azolla) together with a top dressing of 30 kg N/ha as urea showed a similar response in the rice crop.