Soil close to roots generally has chemical, physical and biological properties which are significantly different from those of soil located some distance away (Jenny & Grossenbacher 1963; Hawes & Pueppke 1986; Young 1995). The root–soil interface is defined as soil near to or adhered to the root surface to some small distance into the soil matrix. This distance may vary between <1 mm and c. 10 mm. Working definitions include rhizosphere, where ‘zones of influence’ are inferred, and rhizosheath, when soil adhered to the root is discussed. Most work carried out at the root–soil interface has concentrated on biological or chemical processes, due both to the fact that the relevant techniques required to examine these processes have been more advanced than the physical techniques, and also because the farmer is generally offered either biological or chemical solutions to his everyday problems, as these are readily accessible, easy to use and cheap. The main manipulation of soil physical conditions occurs during cultivations, and the addition or removal of water from the soil profile. Intensive cultivations are a regular occurrence in many farming systems, despite the potential drawbacks: damage of the soil structure, leading to reduced crop yields and an increased risk of erosion.

The main aim of this review is not to cover all the complex issues related to the root–soil interface. Instead, it concentrates on the biophysical processes which, compared with conventional plant physiological and soil microbiological research, have attracted relatively limited attention (e.g. see Waisel et al. 1996). The review examines small-scale (μm-mm) interactions and, where possible, links their impact to the larger scale. Three interacting areas are investigated: the physical structure of the soil and root growth, water dynamics and microbial dynamics.

A series of three experiments on loam to sandy loam soil at Woburn, all following winter or spring wheat, tested the effects of six different 1-year set-aside treatments and crops of winter wheat in 1989, 1990 and 1991 on two following winter wheat test crops. Effects of the treatments on overwinter changes in soil mineral nitrogen (SMN) and plant N in the set-aside years and in the first test crops were measured, as were the grain yields of both the first and second test crops.

Differences in net overwinter changes in SMN plus plant N between set-aside treatments were variable and dependent on rainfall. During a wet winter, SMN plus plant N losses were large under fallow and natural regeneration, intermediate under winter wheat and small under Italian ryegrass (Lolium multiflorum). Ryegrass restricted the growth of the following wheat but yields were unaffected where fertilizer N was applied. Ryegrass proved difficult to control in the subsequent wheat test crops. Forage rape (Brassica napus) took up large amounts of N but after topping did not compete well with weeds.

Yields of the first wheat test crops after winter wheat were smaller than after the set-aside treatments, take-all was probably the cause of this yield depression. No consistent yield differences were recorded in the second wheat test crops.

A survey of soil and root samples collected beneath some pioneering plants colonizing reclaimed mine spoil at an opencast coal mine site at Chandrapur, Maharashtra State, India, was conducted in October 1994 to examine the possible host and edaphic influence on the occurrence of arbuscular mycorrhizal (AM) fungi. Thirteen plant species were sampled to determine the mycorrhizal root colonization and the number of spores of individual AM fungal species in the rhizosphere.

Typical AM fungal infection was observed in roots of all the plant species examined. Mycorrhizal infection ranged from 20 to 95%. Sampled soils contained six spore-forming species of AM fungi (Acaulospora scrobiculata, Entrophospora colombiana, Glomus aggregatum, Glomus ambisporum, Scutellospora calospora and a previously undescribed species of Glomus). Fungal spore densities were not related to the mycorrhizal infection levels. E. colombiana and G. ambisporum were the leading species in terms of spore densities and frequencies. Phenotypic variations in spores of AM fungi were possibly related to the physical and chemical properties of the mine spoil.

It is concluded that the pioneering plant species on mine spoils can cause the development of different populations of AM fungi. The study also indicates that certain species of AM fungi have broad environmental requirements.

Despite the importance of potato tubers as a source of food and a means of propagation, the initiation, growth and development of tubers and the factors affecting these processes are not well understood. There are many reported studies of the effects of various factors on the initiation of tubers but, for a number of reasons, few have sought to understand the initiation of tubers under field conditions. Most reports are concerned with experiments carried out in growth-rooms, which often used very short stem sections as planting material and in which environmental conditions, especially light intensity, differed greatly from those normally prevailing during the period of initiation in the field. In almost all field experiments, the timing of initiation was not defined or properly assessed; number of tubers was recorded infrequently and maximum number of tubers was rarely, if ever, established. Despite these deficiencies, the initiation of tubers is still widely regarded as a key developmental stage in the crop's life, having profound implications for subsequent growth and development (Ewing 1990; Ewing & Struik 1992). This view was first expressed 30 years ago (Ivins & Bremner 1965; Bremner & Radley 1966) and its general acceptance has greatly influenced studies of the growth and development of the crop. During the intervening years, the study of tuber initiation has been an important aspect of research programmes at the University College of Wales (UCW) Field Station, Tenby, Pembrokeshire (1972–84) and Cambridge University Farm (CUF), Cambridge (1982–95), which have now produced sufficient data for a re-evaluation of the significance of tuber initiation in field-grown potato crops.

Great bustard (Otis tarda) populations in Spain are located mostly in cultivated areas during winter. The birds concentrate in large flocks and feed on cultivated plants. This paper reports two types of bustard-caused damage which occur in cereal, lucerne and vetch crops in west-central Spain, as a result of grazing and other bird activities such as display. Field work was carried out between 1994 and 1995. Damage to cereal crops was caused during germination and early seedling growth or to young plants, although plants were able to recover from this by regrowth and the overall yield was not reduced. Vetch crops were damaged in localized areas, but these recovered and were useful for forage enrichment or as grain. However, the damage to lucerne plots, although local, was extensive, resulting in yield losses of 23–31% with respect to the total production.

The responses to fertilizer N of winter wheat and winter barley grown on sandy soils were measured in 74 experiments in England from 1991 to 1994. A series of curves was fitted to the data from each of the experiments to determine which best described the yield response to fertilizer N. The linear plus exponential model, adopted for data from a range of other soil types, with the rate parameter (r) determined for each experiment, proved to be the most satisfactory for these data. The median value of r at 0·987 was less than has usually been determined for other soil types, and was reduced by increasing moisture stress in June, suggesting that the reduced efficiency with which recovered N produces assimilate is partly a result of moisture stress. The model produced a mean Nopt of 143 kg/ha following cereals.

Soil N supply in spring (SNSs) was small at c. 45 kg/ha and commensurate with a large requirement for fertilizer N. Apparent fertilizer recovery (AFR) at 0·70 was greater than that previously measured on clay or chalk soils, suggesting that AFR was not restricted by lack of soil moisture. The larger AFR is considered to be a consequence of more rapid remobilization of fertilizer N in these sandy soils. The greater recovery of fertilizer N reduced the optimum requirement for fertilizer N. Nitrogen harvest index (NHI) was decreased from 0·76 to 0·70 as fertilizer N increased from 0 to 300 kg/ha, whereas dry matter harvest index (HI) decreased from 0·53 to 0·50. The economic optimum requirement for fertilizer N, at 143 kg/ha, was less than reported for other soil types.

The increase in grain yield from applied fertilizer N was less in these experiments than in those reported on other soil types in the UK. However, this overall observation masks two counterbalancing differences. Fertilizer N was recovered more efficiently on these soils; the recovered fertilizer N was used with similar efficiency to produce grain dry matter. The explanation proposed is that on these soils a large proportion of soil water is readily available to crops, and this was taken up rapidly in May accompanied by fertilizer N. However, shortage of water in June restricted the ability of the crop to produce assimilate from fertilizer N applications >c. 150 kg/ha.

Six management regimes for 1-year set-aside were compared with continuous winter wheat for their effects on weed control in two following test crops of winter wheat. The experiment was repeated in each of three years (1989–91) on predominantly sandy loam soils in eastern England. The weed flora was dominated by Poa spp., Stellaria media, Matricaria spp., Chenopodium album and volunteer crops, predominantly wheat.

Managing set-aside by allowing natural regeneration and cutting it 2–4 times during the growing season resulted in fewest weeds in the following wheat crop. It was also a low cost option. Winter wheat, despite the application of herbicides, was not as effective in minimizing weeds in the winter wheat test crops as the best set-aside options.

An Italian ryegrass cover crop set seed despite being cut 2–4 times per year. The only serious weed infestation arising in following wheat crops was from volunteer ryegrass in the second wheat following set-aside. The effects of management in the set-aside year were generally greater in the second of the following wheats than in the first.

The effect of seedbed conditions at the time of sowing on the grain yield and quality ex-farm of spring-sown malting barley was examined in three experiments in the south-east of Ireland in 1993–95. Blenheim malting barley sown in good seedbed conditions gave significantly (P<0·05) greater yields (3·1–9·6% more) than the identically treated crop, sown several days earlier, in less suitable seedbed conditions in all three experiments, but there was no effect on grain nitrogen content or the amount of screenings. The better soil conditions gave significantly (P<0·05) better plant emergence, a greater number of fertile tillers and more grains per ear.

The available world collection consisting of 257 accessions of the tropical pasture legume Centrosema brasilianum (L.) Benth. was assessed between 1993 and 1995 in northern Nigeria to complement existing knowledge on the genetic diversity of this species and to identify accessions with high agronomic potential for subhumid west Africa. The excellent nutritive value and good dry matter productivity of C. brasilianum and its outstanding ability to remain green over extended dry periods confirmed its potential as an important forage resource, especially for the dry season, and indicated its possible role in soil conservation. Two distinct groups, comprising 10 and 11 accessions, were identified for further evaluation in short fallow and pasture systems, respectively. Accessions in the first group had a fast establishment, very high yields in the establishment year and good drought tolerance but yields were low to average in subsequent years. Accessions in the second group had sustained high yields under grazing, a high competitive ability and good drought tolerance.

Diverse cultivars of winter wheat (Triticum aestivum L.) were grown in the field in 1993/94 and 1994/95 at Reading UK in temperature gradient tunnels at normal atmospheric (c. 370) or elevated CO2 concentration (c. 700 μmol CO2 mol−1 air). In 1993/94, grain yield of cv. Avalon was insensitive to mean temperature (between 8·8 and 10·9°C), while elevated CO2 increased yield by 1·3 t ha−1 (12·6%). In all other cultivars, warming reduced grain yield and CO2 increased grain yield. In 1993/94, in cvs Galahad and Mercia the effects of CO2 and temperature on yield were additive. However, for cv. Hereward in both years and for cv. Soissons in 1994/95, there were negative interactions between the effects of CO2 and temperature on yield: the maximum benefit of doubling CO2 to grain yield, 4·5 and 2·7 t ha−1 (65 and 29%) respectively, occurred at cooler temperatures; there was no benefit from doubling CO2 (i.e. 0%) once the temperature had increased above the seasonal mean by 2·2–2·6°C in cv. Hereward and by 1·3°C in cv. Soissons. The beneficial effect of doubling CO2 on grain yield in cvs Galahad, Hereward, Mercia and Soissons was negated by an increase in mean seasonal temperature of only 0·7–2·0°C. Warming decreased root dry mass at anthesis in 1994/95 while it increased at elevated CO2 (49 and 186%, coolest and warmest regime, respectively). Carbon partitioned to roots declined progressively with warming, while at elevated CO2 there was an average of 56% increase in allocation to roots. The relative impacts of both CO2 and temperature were greater on root dry mass than on either grain yield or total above-ground biomass, while the effects on grain and biomass yield varied considerably between cultivars, suggesting that the impact of rising CO2 and temperature are likely to be dependent on cultivar.

Twenty-eight F1 hybrids of wheat and their parents were grown in field trials at Trumpington, Cambridge during 1986/87 and 1987/88. They were derived from crosses between seven ‘modern’ varieties, used as female parents, and either two ‘old’ (Squareheads Master and Partridge) or two ‘modern’ varieties (Bert and Motto), which were used as male parents. Grain yield, yield components, biomass and height were determined. The male parents were chosen to provide contrasting phenotypes and genetic backgrounds for the F1 hybrids. Mid-parent advantage, the increase of a hybrid for a given character above the mean of its parents, and heterosis, the increase of a hybrid above the ‘better’ parent for that character, were calculated. Most F1 hybrids showed mid-parent advantage for the characters studied. This tended to be greatest for hybrids derived from parents with the largest phenotypic differences in that character. In contrast, where heterosis occurred it tended to be greatest where the phenotypic difference between the parents was least. This suggests that the beneficial effects of hybridization, resulting from the dispersion of dominant genes between the parents, was insufficient to overcome the detrimental effects of other genes present where the ‘less good’ parent was substantially lower than the ‘better’ parent. Hybrids derived from the ‘modern’ male parents had greater heterosis for grain yield and mean grain weight than those from the ‘old’ parents. Of the yield components, positive heterosis for mean grain weight resulted in heavier seeds and was the most important yield component in determining heterosis in grain yield. Heterosis for the number of grains/ear was small or did not differ significantly from zero while number of ears/m2 showed negative heterosis resulting in fewer ears/m2 in the hybrids.

Different management regimes for 1-year rotational set-aside were tested in three experiments that followed winter wheat and started in autumn 1988–90. The regimes included operations that prevented the establishment of volunteers or allowed them to establish and persist until either spring or summer, and also altered the distribution of debris from the winter wheat that preceded the set-aside. For comparison, treatments in the set-aside year also included winter wheat.

Samples taken in spring from the first test crop showed that there were few significant or consistent effects on leaf diseases of growing the wheat after different set-aside treatments or after winter wheat. There were significant effects of the set-aside treatments on root and stem base diseases but some of the effects, and the apparent absence of others, are not easily reconciled with current understanding of the biology of the pathogens concerned. In summer, eyespot (Pseudocercosporella herpotrichoides) was most severe after winter wheat and least severe after ryegrass. Severity after the other set-aside treatments did not differ significantly. There was more sharp eyespot (Rhizoctonia cerealis) in plots that had been ploughed at the start of the set-aside year, including those sown with winter wheat, than in those that had not. Brown foot rot (Fusarium spp.) was equally severe where the wheat followed wheat or where it followed set-aside treatments that allowed volunteers to develop, and less so where the development of volunteers was prevented. Take-all (Gaeumannomyces graminis var. tritici) was most severe after winter wheat and more severe after set-aside treatments that allowed volunteers to develop and survive through the winter than after those that did not. Effects of ryegrass (Lolium perenne ssp. multiflorum) on take-all in the following wheat were particularly variable, perhaps because ryegrass is a host of both the take-all fungus and of Phialophora graminicola, one of its principal antagonists.

The progress of leaf emergence, external morphology and apical development stages were recorded in sowings of triticale (cv. Lasko) made from February to November 1990 at Aberdeen (57° N). Leaf appearance and the number of primordia were related to thermal time (above a base of 0°C) except when photoperiods were <c. 11 h. The thermal time per phyllochron varied between leaves and the combined times for all the phyllochrons at a particular sowing accounted for the apparent response of average phyllochron to sowing date. The thermal time requirements for progression to the double ridge stage, terminal spikelet stage, onset of stem elongation and anthesis were similar except where photoperiods of <11 h occurred. The rate of grain primordium production was constant when photoperiod had been increasing at seedling emergence but the rate was reduced when the seedling experienced shortening photoperiods at emergence.

The poor viability of the perennial aromatic grass, palmarosa (Cymbopogon martinii Stapf. var. motia), in the first year of planting, restricts its popularity among farmers in India. Two pigeonpea cultivars, Bahar (late maturing), and UPAS–120 (early maturing) were intercropped at different row spacings with palmarosa at a row spacing of 60 cm, in the subtropical climate of Lucknow, north India in 1988/89 and 1989/90. Intercropping with the late maturing cv. Bahar at 300 cm row spacing produced 1·26 t/ha grain (2-year mean) without affecting the growth and yield of the palmarosa. Intercropping improved land-use efficiency by 47%, relative net return by 58% and net economic return by Rs. 12500/ha over a sole palmarosa crop. The grain, stalk and total dry matter yield per plant of pigeonpea was considerably improved when grown at the wider row spacing in the intercropped system than when grown as a sole crop. This indicates that the competition between pigeonpea plants was not reduced when palmarosa was present. Palmarosa tiller production and herb and oil yield were significantly reduced when the distance between rows of pigeonpea was narrowed, demonstrating both the greater susceptibility of palmarosa to lack of light, and also that in palmarosa–pigeonpea intercropping systems, competition exists mainly for light rather than for nutrients and moisture, possibly because the two crop components acquire their nutrients and moisture from different soil layers.

Intercropping with the high yielding, late maturing pigeonpea cultivar, Bahar, at 300 cm row distance is recommended to make palmarosa cultivation economically viable in the first year of planting. The selection of high yielding, late maturing pigeonpea cultivars with an upright growth habit is suggested as a further way of improving the economic benefits of a palmarosa–pigeonpea intercropping system.

The effect of a comprehensive (three-spray) fungicide programme on yield, specific weight (SW), 1000-grain weight (TGW), nutritive value and yield of both winter and spring oat grains was investigated over a 3-year period (1989–91). With winter oats, four cultivars (Aintree, Image or Pennal, Solva and Kynon), were tested at each of three sites (Gwent, Hereford and Kent). Similarly for spring oats, four cultivars (Dula, Keeper, Rollo and Rhiannon) were tested at each of three sites (Cornwall, North Yorkshire and Wales).

On winter oats, fungicide treatment produced a significant increase (P<0·05) in grain yield, but did not on spring oats. Fungicide treatment produced no significant effect on SW, TGW or nutritive value of the winter or spring oats. With winter oats, but not with spring oats, fungicide treatment produced a significant increase (P<0·05) in the yield of digestible (DE) and metabolizable (ME) energy for pigs and ruminants respectively.

The naked oats, Kynon and Rhiannon, had a significantly lower yield, higher SW and lower TGW than the other conventional cultivars (P<0·05). Their oil, fatty acid, protein, DE and ME contents were also significantly higher than the other cultivars (P<0·05). Nevertheless, the yield of protein, DE and ME tended to be less from naked oats than from some of the other cultivars tested.

On winter oats, TGW, protein content and protein yield, dry matter (DM) and fatty acid content and on spring oats, yield, TGW, ME yield, DM, oil, fatty acid, protein, DE and ME all varied between years. With winter oats, oil content and energy values were negatively correlated with yield and positively correlated with SW. With spring oats, DE and ME were positively correlated with SW.

It was concluded that, on winter oats, fungicide treatment was worthwhile in terms of grain yield, but this was not the case for spring oats. Also with winter oats, but not spring oats, fungicides gave useful increases in the yield of energy. The naked oats, Kynon and Rhiannon, had a distinct advantage in terms of nutritive value, but their low yield compared with the conventional cultivars tended to negate this benefit.

The response of cultivars to applied nitrogen was examined in 11 seasons, 1982–92, in two experiments per year, normally testing seven cultivars at seven rates of fertilizer nitrogen. In all, 27 cultivars were tested in 22 experiments throughout Nottinghamshire, Lincolnshire, Northamptonshire and Suffolk. Cultivars ranged in their date of introduction from Maris Huntsman (1969) to Hereward (1988). For each cultivar in each experiment, the economic optimum yield (Yopt), the amount of fertilizer N needed to produce it (Nopt), the grain %N at Nopt, the offtake of N in the grain at nil N (Noff(N0)) and Nopt (Noff(opt)) and the estimated recovery of fertilizer in the grain at Nopt (AFRopt) were estimated by fitting linear plus exponential curves to data for grain yield and two-straight-line models to data for grain N offtake. From cross-site analysis, normalized cultivar means were calculated for each variate. Over the 20-year period relating to the cultivars in the trial, the contribution of new genotypes to grain yield improvement was 1·92 t/ha, Yopt increasing by 96 kg/ha per year. There was no change in grain %N at Nopt. The effect of changes through breeding from 1969 to 1988 was to increase Noff(opt) by 42 kg/ha (2·1 kg/ha per year), that was associated with a decrease in Noff(N0) (equivalent of soil N offtake) of 15 kg/ha (0·77 kg/ha per year). Part of the increased requirement for fertilizer N was fulfilled by an increase in AFRopt of 18% over the 20-year period. The net effect was for Nopt itself to increase by 56 kg/ha (2·8 kg/ha per year). Since survey evidence indicates no general increase in N use on wheat by farmers since the mid-1980s, it appears that current fertilizer use by farmers may be underestimating the requirement for N now. Alternatively in previous years N requirements may have been overestimated. The change in N available for loss to the environment, from the balance of grain Noff(opt) and Nopt, was from 11 kg N/ha in 1969 compared to 25 kg N/ha in 1988. It seems possible that the potential increase in nitrate levels in groundwater associated with plant type may not have been realised because farmers have conserved the amount of N they use.

Fourteen rice accessions resistant to bacterial leaf blight (BB), caused by Xanthomonas oryzae pv. oryza (Xoo) and belonging to nine wild Oryza species representing three genomic groups: AA (O. nivara, O. barthii, O. longistaminata, O. rufipogon and O. meridionalis), BBCC (O. punctata, O. malampuzhaensis and O. minuta) and CCDD (O. latifolia) were used to produce hybrids with two O. sativa (2n=24, AA) cultivars PR 106 and Pusa Basmati 1 (PB 1). The seed set in similar genome crosses ranged between 1·4 and 79% depending upon the rice cultivar used. In general, PR 106 showed better crossability with the wild species. Hybrids were obtained from intergenomic crosses with O. malampuzhaensis, O. latifolia and O. punctata, using embryo rescue. Morphologically, the hybrids were more vigorous than their parents and tended to resemble their male parent. Intragenomic hybrids showed little fertility (0·24–8·04%), while the intergenomic hybrids were completely sterile. Meiotic studies revealed irregularities in cell division, with a high frequency of univalents (12·17–18·75), fewer bivalents (2·43–5·80) and occasional multivalents, in intragenomic hybrids. The intergenomic hybrids were characterized by a very high frequency of univalents (34·98–35·35). The reaction of the hybrids to BB revealed the presence of both dominant and recessive genes in the wild gene pool. The hybrids with O. longistaminata, O. punctata, O. latifolia and O. malampuzhaensis showed resistance in the F1 generation, and hence they were likely to carry dominant genes for resistance, while the hybrids with O. barthii, O. nivara, O. meridionalis and O. rufipogon were susceptible and hence carried recessive genes for resistance.

Laboratory studies on the biology of oilseed rape (Brassica napus L.) showed that the induction of secondary dormancy is influenced by light environment, time of exposure to light and darkness, temperature regime and genotype. Seeds did not become dormant while exposed to light but were increasingly likely to become dormant the longer they were exposed to water stress and darkness. Dormancy was broken by alternating warm and cold temperatures.

Conclusions from results obtained in Petri dishes have been tested in the field and hypotheses regarding the effects of post-harvest cultivation have been proposed. In July 1995, field experiments were initiated on a flinty silty clay loam and a sand to test the implications of post-harvest cultivation on the development of a persistent seedbank. The results largely confirmed assumptions made on the basis of laboratory findings. Seeds that had been exposed to water stress and darkness for longest, by cultivating the soil at the beginning of the experiment, immediately after seed distribution, exhibited the highest persistence rates. Seeds that were exposed to light for 4 weeks and then incorporated into the soil built up a much smaller seedbank. The seedbank was very small or nonexistent in plots that had not been cultivated at all.

The effect of four seed rates on the grain yield, grain N content and grain size of Blenheim malting barley sown on two dates in the spring was tested on three different soils over a 4-year period (1991–94). The four seed rates (120, 160, 200 and 240 kg/ha) gave mean plant populations of 222, 308, 374 and 430 plants/m2, respectively, for the first sowing date (February to early March) and 235, 340, 405 and 470 plants/m2 for the second sowing date, 3–5 weeks later (late March to mid-April). The earlier-sown crops generally gave greater yield, lower grain N and smaller amount of screenings, but in two of the twelve experiments, the first sowing gave lower yield and greater grain N.

The influence of seed rate on yield and quality depended on sowing date. The three higher seed rates (160, 200, 240 kg/ha) had little influence on yield or grain N, irrespective of sowing date, and there was no significant difference in yield between the lowest (120 kg/ha) and the three higher seed rates when the crop was sown in February and early March. But when the crops were sown in April, the lowest seed rate (120 kg/ha) gave the lowest yield in all seven comparisons and gave significantly reduced yield in three of the seven comparisons. There was a significant increase in grain N in three of the comparisons. Seed rate had little effect on grain screenings or 1000-grain weight. Soil differences did not influence the effect of seed rate on the yield and quality of the grain.

The relationship between initial population density of Globodera pallida and yield was examined for five genotypes of potato at four different experimental sites; two in Scotland and two in England. The experiments at each site were conducted in two stages. The experimental area was first manipulated using resistant and susceptible potato cultivars to give plots with different nematode population densities to act as the initial populations (Pi) for the second stage. The main experiment was conducted using a range of host genotypes that differed in their tolerance and susceptibility. The utility of an inverse linear model relating yield to initial population density was confirmed as were differences in cultivar tolerance. Site differences in yield loss were also observed. It was found that the model could be modified to include the partitioning of genotype and site effects. The implications of this in terms of developing further models to predict yield loss and nematode population dynamics are discussed.