1. Laboratory incubation studies with topsoil samples of the Kikuyu red loam coffee soil have shown that active nitrification of the natural soil nitrogen stops at a soil moisture level just below the permanent wilting percentage. Ammonification of natural nitrogen in this soil does not cease at this moisture level and ammonia nitrogen accumulates substantially, although the values found at the end of the 32-day incubation period, and the rate of ammonification are significantly lower as the moisture level is decreased from ⅚ to of the permanent wilting percentage.

Rumen fermentation characteristics were studied using sheep fitted with rumen cannulae. Diets of 100% hay and 20% hay:80% cooked flaked maize (concentrate diet) were fed at the maintenance level of energy intake as two equal portions per day. Both the gas and liquid phases of the rumen were continuously sampled over 33-h periods.

Concentrations of O2 and N2 in rumen gas inoreased during feeding, whilst concentrations of CO2 and CH4 decreased. Thereafter the concentrations of both CO2 and CH4 rapidly increased. The CO2: CH4 ratio increased rapidly following feeding; it declined to baseline levels 2–4 h after feeding the hay diet, but with the concentrate diet the decline took longer. O2 concentration declined rapidly following feeding and was stable within the range 1–3% for long periods. At no stage was O2 absent from the rumen gas phase. H2 comprised 100–1500 μ1/1 and 100–6000 μ1/1 of the gas phase in sheep fed the hay or concentrate diets respectively and its concentration increased very rapidly with the onset of eating. CO concentration varied between 2 and 16 μ1/1 in the rumen gas of hay-fed animals and was not related to time after feeding. In concentrate-fed animals CO comprised 0—130 μ1/1 of rumen gas and increased very slowly after feeding.

Eh and rH values ranged between —150 and —260 mV and 8·0 and 5·0 units respectively for rumen contents from animals fed the two diets. A diurnal cycle was evident, with the most oxidizing state being attained just before feeding, and the most reducing state just after feeding. The diurnal cycles were better denned by rH than by Eh. The magnitude of the decrease in rH (and pH) during feeding was greater for animals fed the concentrate than the hay diet. At no stage during feeding did Eh or rH change towards more oxidizing conditions. Changes in the concentration of H2 in rumen gas were related to changes in the rH of rumen contents.

VFA molar proportions showed no changes during the 24-h cycle with hay-fed animals but showed erratic variation with concentrate-fed animals. When two sheep fed the concentrate diet were sampled daily for 21 days, it was shown that VFA molar proportions were not constant.

It was concluded that the gas phase of the rumen was never completely O2-free, and that whilst a stable rumen fermentation existed in sheep fed the hay diet the fermentation appeared to be continuously changing in the concentrate-fed sheep, and on this last mentioned diet abnormal values for rumen gas composition and VFA proportions were produced from time to time.

The influence of physiological state (pregnant, lactating, dry) on body composition and fat partitioning in Friesian cows has been examined. A total of 20 cows, four per physiological state, were slaughtered and their left half carcasses dissected into individual muscles, bones and fat depots. All body parts, including the internal organs and fat depots, were weighed at slaughter.

Muscle tissue and the internal organs showed some weight changes, consistent with a redistribution of tissue towards the udder and gut, and mobilization of muscle, but the major changes in weight associated with changing physiological state occurred in total body fat.

Intermuscular fat made the greatest absolute contribution to changing fat weight, but subcutaneous fat showed the greatest proportional change with changing physiological state. The order of depletion of fat depots during fat loss was approximately the reverse of the order of development found during developmental growth.

The distribution of subcutaneous fat between seven defined regions of the carcass was not affected by differences in total fatness in different physiological states. This, and the high correlation found between fat depth and total body fatness, confirms the view that measures of subcutaneous fat depth, e.g. by ultrasonics, should be useful predictors of the energy status of cows in varying physiological states.

The concentration of n-alkanes in the cuticular wax of plants can be used to estimate the composition of the diet selected by free-ranging animals. The aims of this study were to characterize the n-alkane profiles of developing leaves and evaluate the degree of chemical discrimination between six browsed broadleaf tree species: European ash (Fraxinus excelsior L.), flowering ash (Fraxinus ornus L.), hornbeam (Carpinus betulus L.), hazel (Corylus avellana L.), mountain ash (Sorbus aucuparia L.) and beech (Fagus sylvatica L). The effect of the stage of development was examined by considering five different vegetative stages: dormant bud (DB), late bud (LB), young leaf (YL), mature leaf (ML) and senescing leaf (SL). Five samples per each vegetative stage and species, gathered in a mixed woodland of the Italian Eastern Alps between February and October, were analysed for their n-alkane concentrations (C23–C36).

The residual coefficient of variation was 15·5% on average for the individual n-alkanes considered. There were noticeable differences in individual and total n-alkanes content between species. In particular, C27 was the predominant n-alkane in beech and C33 was found in high proportions in the two species of Fraxinus; hazel and flowering ash had a higher total n-alkanes content than the overall mean, while the lowest values were found in hornbeam and beech. The n-alkane profile also underwent important changes during the vegetative development, with different extent and direction according to the species. In the three successive leaf stages, a tendency for a progressive increase in the longest chain homologues was observed. In any case, the young leaf stage differed most from the contiguous stages.

Canonical discriminant analysis indicated that the n-alkane profile of buds and leaves were mathematically distinguishable and the chemical differences between species were persistent over the plant vegetative development.

The effect of level of N fertilizer on the composition, yield and quality of 21 crops was studied in experiments on adjacent sites of the same field to aid in the development of fertilizer recommendations.

Yield of each of the crops first increased and then either remained the same or declined with further increases of N fertilizer. Interpretation by means of a simple model enabled response curves to be characterized by two parameters; one representing the beneficial component of the response and the other the detrimental component. Both varied greatly from crop to crop.

The magnitude of the beneficial component of the response of most non-leguminous crops was largely determined by the potential demand of the crop for nitrogen; the exceptions were some root crops which responded less than would be expected on this basis. The adverse component was serious with root crops and those crops that are in the soil for only a short period. High levels of N increased the ratio of foliage to storage root dry weights even when total dry matter was unaffected. The changes were associated with a considerable increase in the % N in the dry matter of the roots.

When crops were grown with their optimum levels of N fertilizer a simple linear. relationship between the mean %N in the dry matter and the total weight of dry matter per unit area covered all crops. Simple relationships also existed between total dry matter of non-leguminous crops and (a) the amount of N taken up by the crop from unfertilized soil, (b) the recovery of added fertilizer by the crop and (c) the beneficial component of the response of crops harvested before October.

Percentage N in the dry matter at harvest was not a sensitive indicator of the extent to which plant growth was restricted by lack of nitrogen; a difference of 0·1% N in the plant material was associated with a 10% increase in yield.

N fertilizer levels influenced the % dry matter and the incidence of crop disorders such as rotten roots and tissue discoloration, but the effects were seldom appreciable with practicable levels of fertilizer application.

Food utilization by lactating dairy cows was studied in a randomized experiment covering the first 24 weeks of lactation, with further observations on performance over the remainder of the lactation under farm conditions. Over a 3-year period 90 firstcalf cows each took part in the experiment for one lactation, making six groups of 14–16 animals.

For the experimental period a fixed basal diet was given of hay, concentrates, and wet brewer's grains. One group received only the basal ration. Four groups received in addition a fixed concentrates supplement for 4, 8, 12, 16 weeks from calving onwards respectively. The sixth group also had supplementary concentrates for 16 weeks but for weeks 5–12 inclusive the amount was doubled so that this group's diet simulated broadly ad libitum feeding in early lactation.

Milk yield was increased by extra concentrates. The greater part of the effect was apparent in the first 2 weeks of different levels of intake, with a further build-up over the next 6–8 weeks. The size of the response fell as time from calving to initiation of different intakes increased. Additional food increased and delayed peak yield level. Persistency of milk yield was not affected by fixed differences in intake. Rate of liveweight change was improved by extra concentrates, less so in the third compared with the first month on treatment.

A higher level of feeding in early lactation led to a greater partition of nutrients in mid-lactation to milk at the expense of gains in body reserves. This advantage to milk production extended to the end of lactation. In it the greatest response per unit concentrates was obtained from supplementation in the first 4 weeks of lactation but the total effect was increased by giving a double allowance of concentrates, and by extending the period of extra feeding to 8 weeks after calving.

Solids-not-fat content and yield, and fat yield but not fat content, showed a similar response pattern to milk yield.

Animal-to-animal variation in output on constant diets was characterized by negative regressions of live-weight change on milk yield. The regression coefficients were greater in early than in mid-lactation but they were constant in size at any one time for the various groups. A change in ration induced a change in output of the individual in which that production pathway favoured naturally by the animal was the more affected.

The UK rural economy is increasingly driven by consumption-based demands rather than by productive land use. Such demands have been an influence on rural land use for many hundreds of years, but a range of factors, including greater wealth and mobility, have reinforced a long-standing trend for the rural economy to be consumption driven. A number of recent economic analyses and more anecdotal sources are used to furnish evidence of the importance of new consumption demands. It is argued that such demands may impact directly on land markets through land purchase for amenity, etc. and indirectly through bringing affluent people into closer proximity to diversified business opportunities. It is argued that these new economic realities are the dominant drivers of economic change and that their recognition might suggest new approaches to the support of strategies to deliver more sustainable rural development.

1. The nitrogen content of an arable soil to 15 cm depth, sown to a ryegrass/white clover sward increased on average by 0·005 % N each year.

2. Under a grass sward without clover and without fertilizer nitrogen, there was an increase of 0·017 % N in 3 yeais in the top 7·5 cm of soil; an annual addition of about 70 kg N/ha.

3. Including white clover in grass swards not receiving nitrogen fertilizer resulted in an increase over 3 years of 0·026% N to 7·5 cm depth in one experiment, and 0·014% N to 15 cm depth in another, an annual increment of 100–110 kg N/ha.

4. The increase was greater under ryegrass/white clover swards than under cocksfoot/white clover swards. A similar difference was found both in accumulation of organic carbon and in clover content. In an experiment comparing many different grasses it was not possible to distinguish differences in the level of soil nitrogen, after 4 years under grass, which could be ascribed to species or strains.

There was no significant effect of nitrogen fertilizer applied at rates of up to 314 kg N/ha per year for 3 consecutive years.

Treatments which lowered the rate of ammonia volatilization from surface-applied cattle slurry were evaluated in three field experiments during 1989/90 at the Agricultural Research Institute of Northern Ireland. The relative effects of separation, dilution with water before application and washing with a water spray after application, on ammonia volatilization rates were compared over 4 days using ventilated enclosures. As the loss rate of ammonia during the first 4 days after application was highly correlated with the loss rate over the first 4 hours after application, the loss rate in the first 4 hours was used as a rapid method to assess the efficacy of various combinations of separation, dilution and acidification. Ammonia volatilization loss rates from treatment combinations were compared to the loss rate from whole slurry.

A 50% decrease in ammonia volatilization was achieved by separation through a 0·4 mm mesh, separation through a 10·0 mm mesh plus dilution with 86% by volume of water, or separation through a 2·0 mm mesh plus washing with 53% by volume of water.

A 75% decrease in ammonia volatilization was achieved by acidification to pH 6·5, or combinations of separation and dilution, namely separation through a 0·4 mm mesh plus 50% dilution or separation through a 5·0 mm mesh plus 100% dilution.

A 90% decrease in ammonia volatilization was achieved by acidification to pH 6·0, dilution by 50% plus acidification to pH 6·5, or separation through a 0·4 mm mesh plus acidification to pH 6·5.

The effects of separation and acidification on ammonia volatilization were cumulative. There was a highly significant inverse linear relationship between ammonia volatilization rate and volume of nitric acid used. Adding 10 M nitric acid at 1·4% by volume lowered volatilization by 75% of that from whole slurry and increased the nitrogen content of the slurry by 2 g N/l, making it a more balanced NPK fertilizer for cut swards. Because the variable value of cattle slurry is due to loss of nitrogen as ammonia and smothering of the sward with slurry solids, a combination of separation or dilution to lower sward contamination and acidification with nitric acid to lower volatilization may be the best practical option for improving cattle slurry as a fertilizer for cut grass.

Two experiments at Belclare, Co. Galway, in late autumn 1988, evaluated the use of herbage and dosed n-alkanes for estimating herbage intake by sheep. The first experiment examined faecal recoveries of dosed and herbage n-alkanes. The second experiment assessed the accuracy and precision of herbage intake estimates obtained using the n-alkane technique, and tested the effect of supplying n-alkanes to animals either in gelatine. capsules (containing different ratios of n-alkane: cellulose fibre) or in pellets prepared from shredded paper onto which the n-alkanes had been adsorbed. Individually penned wether lambs were offered freshly cut herbage ad libitum (+ 10%) and actual dry matter intake was recorded daily. Intake was estimated using the C31:C32 and C33:C32 (natural:dosed) n-alkane ratios.

There was no significant effect of n-alkane chain length on faecal recovery rate for either the dosed n-alkanes (C32 and C36), the herbage odd-chained n-alkanes (C29, C31, C33 and C36) or those used for the estimation of herbage intake (C31, C32 and C33). The accuracy and precision of the n-alkane technique for estimating herbage intake were unaffected by whether the dosed n-alkane was supplied in capsules or pellets or by the n-alkane:cellulose fibre ratio in the capsules. The bias in the estimated intake was – 8% (± 1·1%) and + 3% (± 1·2%) for estimates based on C31:C32 and C33:C32 ratios, respectively. The estimates based on C31:C32 and C33:C32 exhibited similar precision in the estimation of herbage intake, with a R.S.D. of 6% in actual intake when adjusted for variation in estimated intake and a correlation of +0·92 between actual and estimated herbage intake. The C.V. for actual herbage intake was 17%. The repeatability of actual dry matter intake over three consecutive 6-day periods was 0·54 while those of estimated intake were 0·57 and 0·60 for estimates based on C31:C32 and C33:C32, respectively. The results show that the n-alkane technique can provide an accurate and precise estimate of herbage intake.

The effect of oestradiol-17β on the response to fishmeal supplementation of grass silage was studied in young growing cattle. Voluntary intake and live-weight gain were recorded over 63 days with 36 British Friesian male castrates (initial live weight (LW) 119 kg) offered silage alone (C) or with 50 (FM1), 100 (FM2), or 150 (FM3) g fishmeal/kg silage dry matter. Twelve calves were allocated to each of treatments C and FM3 and six to treatments FM1 and FM2. Half of the calves on each treatment were ear-implanted with oestradiol-17β (Compudose 365) at the start of the experiment. The calves on treatments C and FM3 were slaughtered after 75 days and chemical analysis conducted on half of each carcass. The silage had an organic-matter digestibility in vivo of 0·794 and was well-fermented, with a pH of 3·7. Intake averaged 24·2±0·42 g D.M./kg LW over all the treatments and live-weight gain was 0·77 kg/day on the silage alone. There was a significant (P < 0·05) interaction between fishmeal and oestradiol-17β, such that response to the hormone was observed only in the presence of fishmeal at 100 or 150 g/kg silage D.M. A similar interaction was apparent between fishmeal at 150 g/kg silage D.M. and oestradiol-17β in the final weights of empty body and carcass. This level of fishmeal also increased protein gain from 96 to 147 g/day and this was further increased to 179 g/day in the implanted animals receiving fishmeal. However, the overall effect of oestradiol-17β on protein gain was not significant. Gross efficiency of energy utilization was significantly (P < 0·01) increased by fishmeal supplementation suggesting an improved balance of nutrients compared with the silage alone diet.

1. A series of grazing behaviour observations on 10 sets of lactating identical twins is described. Four fortnights distributed over the main lactation period were covered. In three of the fortnights, the observations were made on six 24 hr. periods, while in the remaining fortnight the cows were observed on all 14 days.

2. Anoutstanding feature of the grazing behaviour of dairy cattle is its variability, due to external and internal conditions.

3. Of the external factors, climate (in a temperate zone) is relatively unimportant.

4. The quantity and quality of the herbage offered are of importance in modifying the grazing behaviour of dairy cattle. Under adverse pasture conditions there is, in general, an increase of total working time (grazing + ruminating): grazing time increases with scarcity of herbage and with mixed quality, while ruminating time is prolonged by poor quality grass.

5. Ruminating time is strongly dependent on the quantity and quality of the ingested grass, but the relationship is, for various reasons, obscured in a field trial such as the present.

6. The adaptation of grazing habits to new conditions is very rapid.

7. Feed requirement for milk production is the most important internal factor determining variation in the length of grazing time.

8. Inheritance × environment interactions as a source of variations in grazing times are due to the following factors:

(a) Differences amongst twin sets in lactational persistency, which presumably cause parallel differences in feed requirements.

(b) Differences in the response of high and low producing twin sets to varying pasture conditions.

(c) Non-analysable idiosyncrasies common to the members of some twin sets.

9. Twin sets graze and ruminate at a characteristic rate.

A scheme was developed to describe how the rate at which apical primordia are initiated in cereals depends on temperature and photoperiod. It was used to analyse initiation in field crops of winter wheat (Triticum aestivum L., cv. Maris Huntsman).

For the initiation of leaves and spikelets, a straightforward linear regression of initiation rate R against mean air temperature (Ta) gave base temperatures (Tb) close to 0 °C for leaves and for spikelets. However, initiation rate was also correlated with mean photoperiod (P) and base photoperiods (Pb) of –0·5 h and 4h were established for leaf and spikelet initiation. When R was correlated with the index (T – Tb) (P – Pb), r2 was 0·62 for both leaves and spikelets.

Fifteen grassland species were grown in a heated glasshouse in February-April 1985. The harvested herbage was separated into leaf and ‘stem’ and analysed for neutral detergent fibre, digestibility, physical breakdown when macerated, fibrosity, water soluble carbohydrate and N, P, K, Ca, Mg and Na.

Lolium perenne was digestible, but rather high in neutral detergent fibre and not readily broken down by maceration. The other grasses tested, Holcus lanatus, Poa annua and Glyceria fluitans, tended to be less digestible and higher in neutral detergent fibre than L. perenne.

The leaves of all 11 dicotyledonous species were much lower in neutral detergent fibre than the leaves of the grasses, and most broke down readily when macerated. The stems of Medicago saliva and of two shrub species (Lonicera periclymenum and Prunus spinosa) were the highest in neutral detergent fibre.

Rumex obtusifolius, Spergula arvensis and Stellaria media were high in Mg; Plantago lanceolata, S. arvensis and S. media were high in Na; and S. arvensis was high in P.

Three perennial and two annual herbaceous, dicotyledonous non-legumes were selected as being of sufficient promise and interest to be compared with Lolium perenne in feeding experiments: Plantago lanceolata, Taraxacum officinale, Rumex obtusifolius, Spergula arvensis and Stellaria media.

The transition from conventional to organic farming is accompanied by changes in soil chemical properties and processes that could affect soil fertility. The organic system is very complex and the present work carries out a short-term comparison of the effects of organic and conventional agriculture on the chemical properties of a silty loam soil (Xerofluvent) located in the Guadalquivir River Valley, Seville, Spain, through a succession of five crop cycles over a 3-year period. Crop rotation and varieties were compared in a conventional system using inorganic fertilizer and two organic systems using either plant compost or manure. At the end of the study, organic farming management resulted in higher soil organic carbon (OC), N and available P, K, Fe and Zn. The available Mn and especially Cu values did not show significant differences. In general, treatment with manure resulted in more rapid increases in soil nutrient values than did plant compost, which had an effect on several crop cycles later. The present study demonstrated that the use of organic composts results in an increase in OC and the storage of nutrients, which can provide long-term fertility benefits. Nevertheless, at least 2–3 years of organic management are necessary, depending on compost characteristics, to observe significant differences. Average crop yields were 23% lower in organic crops. Nevertheless, only two crops showed statistically significant differences.

Remotely sensed estimates of biochemical parameters of agricultural crops are central to the precision management of agricultural crops (precision farming). Past research using in situ and airborne spectral reflectance measurements of various vegetation species has proved the usefulness of hyperspectral data for the estimation of various biochemical parameters of vegetation. In order to exploit the vast spectral and radiometric resources offered by space-borne hyperspectral remote sensing for the improved estimation of plant biochemical parameters, the relationships observed between spectral reflectance and various biochemical parameters at in situ and airborne levels needed to be evaluated in order to establish the existence of a reliable and stable relationship between spectral reflectance and plant biochemical parameters at the pixel scale. The potential of the EO-1 Hyperion hyperspectral sensor was investigated for the estimation of total chlorophyll and nitrogen concentrations of cotton crops in India by developing regression models between hyperspectral reflectance and laboratory measurements of leaf total chlorophyll and nitrogen concentrations. A comprehensive and rigorous analysis was carried out to identify the spectral bands and spectral indices for accurate retrieval of leaf total chlorophyll and nitrogen concentrations of cotton crop. The performance of these critical spectral reflectance indices was validated using independent samples. A new vegetation index, named the plant biochemical index (PBI), is proposed for improved estimation of the plant biochemicals from space-borne hyperspectral data; it is simply the ratio of reflectance at 810 and 560 nm. Further, the applicability of PBI to a different crop and at a different geographical location was also assessed. The present results suggest the use of space-borne hyperspectral data for accurate retrieval of leaf total chlorophyll and nitrogen concentrations and the proposed PBI has the potential to retrieve leaf total chlorophyll and nitrogen concentrations of various crops and at different geographical locations.

Part I, largely introductory, outlines the design of an experiment to measure the responses of ordinary farm crops to supplementary irrigation in a part of England where, from meteorological reasoning, the frequency of need was expected to be about 2 years in 3. The watering treatments were based on estimates of potential transpiration, made from weekly weather data collected on the site, and measured rainfall. The basis of the computation is restated, and the balance of rain and estimated transpiration plotted for each of the 9 years, week by week in summer, month by month in winter. The meteorological specification of frequency of need was satisfied in 5 of the years, during which twenty crops were taken. Of these, eighteen responded to irrigation. In the other years, four of the sixteen crops responded positively to irrigation, and a few of the remaining twelve responded negatively when early irrigation was followed by summer rainfall sufficiently in excess to cause leaching from irrigated plots.

Yield responses of some economically important crop plants due to foliar applications of low concentrations of 28-homobrassinolide (HBR) were studied in experiments conducted at research stations and in farmers' fields in India during 1989–95. Foliar sprays of different concentrations of HBR were applied at tillering and spike/panicle initiation in wheat (0·5 and 1·0 mg/l) and rice (0·25, 0·50 and 1·00 mg/l); at flowering and pegging in groundnut (0·25 and 0·50 mg/l); 30 and 45 days after sowing (DAS) in mustard (0·25 and 0·50 mg/l); 25 and 35 days after emergence in potato (0·25 and 0·50 mg/l); and 30, 50, 70 DAS in cotton (0·1 and 1·0 mg/l). The HBR treatments significantly (P<0·05 and P<0·01) increased grain yields in wheat, rice and mustard, pod yields in groundnut, tuber yields in potato and seed cotton yields, over control. The extent of yield improvement due to HBR was influenced by crop species, concentration of HBR, plant growth stage at application and frequency of application.

Examples of response surfaces for pairs of nutrients and results of 41 multi-level experiments with N only were used to compare the goodness-of-fit of polynomial, inverse polynomial, exponential and intersecting-straight-lines models.

Whereas no one model fitted best at every site, many results were well represented by two intersecting straight lines and on average, this model had the least residual mean square. Of 17 experiments with spring barley in south western England the few results best represented by smooth curves were from crops much affected by leaf diseases.

Fertilizer response was poorly represented by models without a falling asymptote, like the simple exponential and inverse linear. Study of residuals after fitting the quadratic showed that this widely used model consistently over-estimated both the amount of fertilizer needed for maximum yield and the yield loss when too much fertilizer was given.

When fitted to the mean yields of each nitrogen treatment, most models had residual mean squares equal to or less than the error mean square, repeating a result obtained at Rothamsted as early as 1927. We question the validity of some well-known evidence for block and treatment additivity.

For 12 experiments in 1970, between-site differences in the parameter values of the two straight lines representing grain yield were related to leaf area at ear emergence.

Visible (VIS) and near-infrared reflectance spectroscopy (NIRS) combined with multivariate data analysis was used to predict potentially mineralizable nitrogen (PMN) and nitrogen in particulate organic matter fractions (PSOM-N). Soil samples from a long-term experiment (n=24) as well as soils under commercial management (n=160) in Uruguay (South America) were analysed. Samples were scanned in a NIRS 6500 monochromator instrument by reflectance (400–2500 nm). Modified partial least square regression (MPLS) and cross validation were used to develop the calibration models between NIRS data and reference values. NIRS calibration models gave a coefficient of determination for the calibration (R2CAL)>0·80 and the standard deviation of reference data to standard error in cross validation (RPD) ratio ranging from 2 to 5·5 for the variables evaluated. The results obtained in the study showed that NIRS could have the potential to determine PMN and PSOM-N fractions in soils under different agronomic conditions. However, the relatively limited number of samples led us to be cautious in terms of conclusions and to extend the results of this work to similar conditions.