Seedbed fertilizer requirements of winter oilseed rape

Thirty-four field experiments were carried out on the seedbed fertilizer requirements of winter oilseed rape in the main rape-growing areas of England and Scotland. Average seed yield was increased by seedbed N from 2.711 ha^?1 to 2.881 ha^?1 (when 200 kg ha^?1 N was given in spring). Economic analysis showed 60 kg ha^?1 as likely to be the most profitable rate of seedbed N for most situations. P fertilizer increased yield significantly on soils with low or moderate levels of available soil P but there was little response to K fertilizer on soils of high or medium K status and too few experiments on low K status soils to quantify requirements thereon. S application to the seedbed (as calcium sulphate) did not increase yield. Seedbed N decreased seed oil content slightly and not always significantly while P, K and S had no effect. Nutrient removal in the seed of an average 3 t ha^?1 crop would be 90 kg ha^?1 of N, 17 kg ha^?1 of P (40 kg ha^?1 P₂O₅) and 17 kg ha^?1 of K (20 kg ha^?1 K₂O).     

Effect of nitrogen application rate on the content and composition of oil,essential oil and minerals in black cumin (Nigella sativa L.) seeds

A field experiment was conducted to study the effect of nitrogen fertility level on the content and composition of oil, essential oil and minerals in black cumin (Nigella sativa L.) seeds. Sixty‐three‐day‐old plants were supplied with varying levels of N, i.e., 0, 30, 60, and 90 kg N ha^?1 soil. The fixed oil content of the seeds ranged from 32.7% to 37.8% and it remained almost unchanged at the two higher external N regimes, i.e., 60 and 90 kg N ha^?1, but at 30 kg N ha^?1 the oil content increased significantly. Of the saturated fatty acids analyzed, palmitic acid increased slightly at all external N levels, but in contrast stearic acid decreased considerably at 60 kg N ha^?1. Of the unsaturated fatty acids of fixed oil, the predominant fatty acid was linoleic acid (18:2) followed by oleic acid (18:1). Linoleic acid and dihomolinoleic acid (20:2) showed no change in their amounts at varying levels of N. In contrast, a marked reduction in α‐linolenic acid (18:3) was found at the two higher N regimes, i.e., 60 and 90 kg N ha^?1. Seed essential oil content did not vary with the change in applied N level. The major component of essential oil of black cumin seed was found to be p‐cymene, which showed an increase at 30 kg N ha^?1, whereas no change in the levels of α‐pinene or β‐pinene was observed at varying levels of N. K, P, Na, Fe, Mn, and Ni were found to be predominant elements in the seeds. Ca, Mg, Cu, and Cr were present in low amounts, but Zn was present in moderate quantity. Increasing N rate did not affect the content of K, P, Ca, Mg, or Cr in the cumin seeds. In contrast, a consistent decrease in seed Mn, Zn, and Ni was observed with increase in external N level. Increasing N level had a marked effect on some of the components of black seed oil. Copyright © 2006 Society of Chemical Industry     

The response of double-low winter oilseed rape to fertiliser sulphur

The effect of soil-applied ammonium sulphate (10, 20, 30, 50 and 80 kg S ha^?1) and agricultural gypsum (20 and 50 kg S ha^?1) and of foliar-applied elemental sulphur (20 kg S ha^?1) on the seed yield and chemical composition of double-low cultivars of winter oilseed rape was determined at 11 sites in England during 1989-1991. Significant (P ? 0.05) mean seed yield responses to applied sulphur (S) of 10 and 17% were obtained at two sites on sandy soils in northern England which showed symptoms of severe S deficiency. At a third site on a shallow calcareous soil in south-west England, which did not show S deficiency symptoms, seed yield was consistently but not significantly increased by an average of 8%. At one of the sites in 1989, application of ammonium sulphate caused leaf scorch and, at the maximum rate of S applied, seed and oil yield were decreased. No conclusions were reached regarding the amount of S required for maximum yield response. The S treatments decreased seed oil content by an average maximum of 9 mg g^?1. Seed glucosinolate content was increased by a greater amount at the two sites in northern England compared to other sites, where increases averaged only 3 μmol g^?1. Analysis of individual glucosinolates in the harvested seed from one of the sites in northern England showed that only the alkenyl glucosinolates were increased by S application. Yield responses were best predicted by total S concentrations and N : S ratio values in young fully-expanded leaves at flowering. Foliar-applied elemental S was consistently less effective in raising leaf S content than ammonium sulphate. Gypsum was occasionally found to be less effective than ammonium sulphate as an S fertiliser.     

Sulphur-coated urea as a fertiliser for potatoes

In a field experiment comparing sulphur-coated urea (SCU) and “Nitro-Chalk” at rates up to 400 kg N ha^?1, potato tuber yields were greater with “Nitro-Chalk” at rates up to 200 kg N ha^?1, but there was no consistent difference between forms of N at larger rates. The crop recovered more N from “Nitro-Chalk” at all rates except 350 kg N ha^?1. The largest measured yield was at 200 kg N ha^?1 with “Nitro-Chalk” and 250 kg N ha^?1 with SCU, and the optimum N rate inferred from split-line regressions of yield on N rate was also at a lower N rate with “Nitro-Chalk”. Yields of winter wheat following the potatoes increased significantly with the N rates given to the potatoes and, at rates above 200 kg N ha^?1, were larger where SCU had been used. SCU residues also lessened the response of the wheat to a spring top-dressing of new N slightly more than those of “Nitro-Chalk”. The sum of the apparent recoveries by the two crops of N given to the potatoes was greater from “Nitro-Chalk” at rates up to 200 kg N ha^?1. In the glasshouse, potato plants grown in 3 kg soil took 71 days to initiate tubers when given 2 g N as ammonium nitrate but this time was much decreased as increasing proportions of SCU were used. When 1 g N was given, the time was only 47 days with ammonium nitrate and the proportion of SCU had little effect. In the field, the number of tubers per plant by mid-June decreased with increasing N rate with “Nitro-Chalk” but not with SCU.     

Relationship between N concentration of grain and grain yield in recent winter-wheat experiments in England and Belgium,some with large yields

Eight winter-wheat experiments conducted by Rothamsted on clay soils in 1980 and 1981 formed part of an inter-institute collaborative programme on yield variation. The tests included no N and four amounts of fertiliser N up to 200 kg ha^?1, with and without spray treatments to control pests and diseases. Large grain yields—in excess of 10 t ha^?1—were often obtained, mainly where losses had been limited by sprays. In Belgium, 10 experiments during the same seasons were on a wider range of soils and had spray treatments applied to all plots. Yields exceeding 10 t ha^?1 were obtained at one site. Graphs showing the inter-relationship between grain-N %, grain yield and N uptake are used to compare the recent results with those from a 20-year study of similar data from 124 earlier Rothamsted experiments. The envelope curve delineating the range of yield and grain-N % values from these older experiments enfolded most of the more recent data points, except those deriving from the largest yields which were associated almost entirely with grain-N % values below the minimum recommended for British breadwheat. The largest grain-N uptakes were 180–190 kg ha^?1 and 170–180 kg ha^?1 in the recent Rothamsted and Belgian experiments respectively, compared with 160-170 kg in the older experiments. The linear or near-linear relationship between grain-N % and amounts of fertiliser N, established in the 20-year study, was again observed in the recent Rothamsted and Belgian experiments, with about 38 kg of added N needed to increase grain-N concentrations by 0.1%.     

Effect of residual fertility and direct fertilisation on kernel,protein and oil yield of peanut (Arachis hypogaea L) grown in rice fallows

Kernel (2814–3467 kg ha^?1), protein (555–759 kg ha^?1) and oil (124–1556 kg ha^?1) yields of peanut (Arachis hypogaea L) varied significantly due to the residual effect of organic manures and inorganic fertilisers together. It was also observed that direct application of recommended fertilisers (25 N, 72 P₂O₅ and 37-5 K₂O kg ha^?1) gave the highest kernel (3669 kg ha^?1), protein (786 kg ha^?1) and oil (1606 kg ha^?1) yields. The reduction in kernel, protein and oil yield from the recommended level of fertilisers to half the recommended level of fertilisers was about 16, 15 and 12% while it was about 25, 33 and 27% with no fertiliser. Thus, the results revealed that the nutrients applied partly through organic manures and inorganic fertilisers to Kharif rice exhibits significant residual effects on the succeeding upland crop and hence the fertilisation must be considered not only for individual crops but also for the cropping system as a whole.     

Effect of nitrogen fertiliser on the fatty acid composition of oil from low erucic acid rape varieties

The effect of N fertiliser on the fatty acid composition of two low erucic acid varieties of winter oilseed rape (Primor and Rapora) was investigated in two field experiments in eastern England in 1976. Rates of N from 0 to 270 kg ha^?1 and application times from February to late April were compared. N increased growth and yield and reduced oil content but timing had little influence. Neither rate nor time of N fertiliser had any detectable effect on fatty acid composition in either experiment; the composition was as expected for these varieties, with over 60% oleic acid and 3% or less of erucic acid. It appears that the fatty acid composition of low erucic varieties is little affected by N fertiliser.     

Changes in yield and seed quality traits in rapeseed genotypes by sulphur fertilization

Sulphur is considered more as a soil amendment to remedy alkaline soils rather than a fertilizer in crop production. However, as one of the macronutrients, just as N–P–K, it is able to have a direct and significant effect on yield and quality in some crops. There might be a sound potential of increasing seed yield and quality of rapeseed, the second important oil crop around the world, with the use of sulphur as a fertilizer in cultural practices. Our objective in this study is to determine the effects of sulphur fertilization on seed yield and several seed and oil quality traits in rapeseed. Five rapeseed genotypes were grown for two consecutive growing seasons in Çanakkale, in a RCB design with three replications. The experimental plots were given 0, 100 or 200 kg ha^?1 sulphur along with a fixed amount of 240 kg ha^?1 N. Results indicated that sulphur fertilization had positive effects on seed yield and some of the seed and oil quality components. On the other hand, excessive sulphur fertilization, or naturally occurring high levels in the soil, may have adverse effects in elevating some undesired compounds, such as glucosinolates.     

Some relationships between grain yield and grain protein of wheat experiments in south-east england and comparisons with such relationships elsewhere

By adopting a uniform method of presentation, the interrelationship between grain yield, %N in grain and N uptake (or protein yield) from diverse experiments and surveys can be compared readily. All three variables can be shown together by plotting yield vs %N and adding the third variable in the form of hyperbolic lines representing equal N uptake (or protein yield). This method is used in two diagrams which display 2000 values derived from 124 experiments on winter wheat and 400 values from 41 experiments on spring wheat, conducted by Rothamsted Experimental Station over 20 years. Both scatter diagrams display well-defined boundaries which have been emphasised by linking points along these boundaries to form ‘envelope curves ’For winter wheat the maximum yield was 9.5 t ha^?1, the largest N concentration about 3% and the largest N uptake 170 kg N ha^?1 (about 970 kg protein ha^?1). Spring wheat had a maximum grain yield of 6.3 t ha^?1, the largest N concentration was 3.1% and the largest N uptake 125 kg N ha^?1. Four examples of other work set within the same framework show applications of our method of presentation. Results from a recent more homogeneous series of experiments in southern England (conducted by the Agricultural Development and Advisory Service), showing clear seasonal differences, are seen to lie within the envelope curve defined by the Rothamsted experiments. Further illustrations are taken from an experiment by the Plant Breeding Institute, Cambridge, comparing varieties of different bread-making qualities, from work of the Nebraskan plant breeding team who have produced grain with larger protein content without sacrificing yield, and from survey data for England and West Germany.     

The effect of two harvests per year on the yield and composition of Tasmanian peppermint oil (Mentha piperita L.)

Peppermint (Mentha piperita L.) was harvested on two occasions during the growing season. Double harvesting yielded approximately 140 kg oil ha^?-1. The first harvest was timed to coincide with a period of maximum oil yield per unit area (ca. 70 kg ha^?1) and yielded an oil containing 39% menthol. The oil yield in the subsequent regrowth increased to approximately 70 kg ha^?1, and when harvested at this stage the oil contained high levels of methol (53%). The oils produced from the double harvest programme could either be combined to resemble the Tasmanian single harvest oil or marketed as distinctive oil types. Organoleptic evaluation indicated that oil from crops 1 and 2 resembled Midwest and Yakima Valley, USA, oils, respectively. Double harvesting had no apparent adverse effect on the regrowth in the following season.     

Effect of drought and irrigation on the fate of nitrogen applied to cut permanent grass swards in lysimeters: Leaching losses

Nitrogen losses were measured in water draining from cut permanent grass swards growing in monolith lysimeters containing clay loam (Salop series) or silt loam (Bromyard series) soils. The swards were cut at 6-week intervals during the summer and were fertilised with calcium nitrate at rates of 0 and 400 kg N ha^?1 in each of five successive years (1977–81); in the first year the fertiliser was labelled with ¹⁵N. Four differing rainfall regimes were imposed from spring to autumn in each year. Mean annual losses of nitrogen by leaching from unfertilised swards were 3.8 kg N ha^?1 with mean nitrate-N concentrations in the water of about 1 mg N litre^?1. In fertilised lysimeters where rainfall distribution was that of the long-term average the mean annual total nitrogen losses were 41 kg N ha^?1 in the Salop soil and 15 kg N ha^?1 for the Bromyard soil; mean nitrate-N concentrations were 11.6 mg N litre^?1 and 5.1 mg N litre^?1, respectively. Losses of nitrogen and nitrate concentrations were similar to these quantities when irrigation increased the rainfall total to 120% of average. Where a drought was imposed for 2 weeks before and after each cut, mean nitrate-N concentrations increased to 20.3 mg N litre^?1 on Salop soil and 13.1 mg N litre^?1 on Bromyard soils; total annual nitrogen losses were 74 kg N ha and 33 kg N ha^?1, respectively. The largest losses were recorded when the drought period extended for four weeks before each cut and mean nitrate-N concentrations increases to 28.8 mg N litre^?1 on Salop soil and 34 mg N litre^?1 on Bromyard soil, with total annual nitrogen losses of 104 kg N ha^?1 and 109 kg N ha^?1, respectively. Losses of nitrogen derived from the fertiliser labelled with ¹⁵N were 7.3–8.4% of that applied in the Salop soil (29–33 kg N ha^?1), with little effect by the differing rainfall distributions. On the Bromyard soil, losses were 3.7% (14 kg N ha^?1) of the applied fertiliser in lysimeters not subjected to droughts. When the period of the drought extended before and after each cut, losses were 8.2% (32 kg N ha^?1) and increased to 17.9% (70 kg N ha^?1) when the drought period occurred entirely before each cut. Fertiliser nitrogen contributed 48–69% of the total nitrogen in drainage water from both soils in the first year.     

Interrelationship between nitrogen concentration in grain,grain yield and added fertiliser nitrogen in wheat experiments of South-east England

Results from 20 years of wheat experiments were used to compare responses of grain-N% and grain yield to increasing amounts of fertiliser-N. Grain-N% for both winter and spring wheat increased, mostly linearly, throughout the range, whereas many of the grain yield curves reached a maximum and then declined with further additions of N. Provided curve sections exhibiting dilution effects were excluded, the linear or near-linear relationship between grain-N% and fertiliser-N allowed linear regression models to be fitted. This showed that, over a range of 50-175 kg N ha^?1, an average of 32 kg ha^?1 of fertiliser-N was required for an increase of 0.1% N in grain dry matter of winter wheat or 56 kg N ha^?1 for an increase of 1% protein. Results from 3 years of experiments conducted by the Agricultural Development and Advisory Service (ADAS) agreed closely with those obtained from Rothamsted. Using the linear relationship between grain-N% and fertiliser-N, curves were plotted of grain yield against grain-N, adjusted for comparable additions of fertiliser-N (75, 100, 125, 150 kg ha^?1). The curves tended to have sections with rising yield for small applications of N, to exhibit a maximum in a central zone and descending sections for large applications. There was no well-defined ?critical level’? of grain-N%, beyond which this and grain yield were inversely related.     

Unused fertiliser nitrogen in arable soils—its contribution to nitrate leaching

Nitrate present in arable soils in autumn is at risk to leaching during the following winter. To see whether unused nitrogen fertiliser was a major source of this nitrate, ¹⁵N-labelled fertiliser was applied to 11 winter wheat crops at rates of between 47 and 234 kg N ha^?1in spring. The experiments were on three contrasting soil types in south-east England. On average, 17′% of the N from spring-applied labelled fertiliser remained in the 0–23 cm soil layer at harvest (range, 7–36%) but only a small proportion was in inorganic forms (ammonium + nitrate). This was never more than 5 kg N ha^?1and averaged only 1·3% of the fertiliser N applied (range, 0·4–3·6 %). Between 79 and 98% of the inorganic N in soils at harvest was unlabelled, being derived from the mineralisation of organic N rather than from unused fertiliser. The amount of unlabelled N was much greater where wheat was grown after ploughing up grass or grass/clover leys than where it was grown in all-arable rotations. When wheat was grown without N fertiliser, soil inorganic N content at harvest was no lower than in plots given fertiliser at rates up to 234 kg N ha^?1. This work indicates that, for soil growing winter wheat, almost all of the nitrate at risk to leaching over the winter period comes from mineralisation of organic N, not from unused fertiliser applied in spring. Consequently, even a drastic reduction in N fertiliser use would have little effect on nitrate leaching.     

The effect of the previous crop on the growth,nitrogen uptake and yield of winter barley intended for malting

Winter barley which received a range of nitrogen rates, was grown at Rothamsted as a test crop after winter oats, winter barley, winter beans, oilseed rape or potatoes, to compare the effects of previous crop on growth and N uptake. In the autumn following the first year crops, the largest amount of residual inorganic N found in the soil was after potatoes, the smallest after oats. Throughout the second season the heaviest crops of barley, which also contained the most N, were after potatoes, and the lightest were after barley. To produce grain with a N concentration of less than 1.8% N (w/w, dry wt), acceptable for malting, it was found that not more than 75 kg N ha⁻¹ after barley and 125 kg N ha⁻¹ after oats, 100 kg N ha⁻¹ after beans and 50 kg N ha⁻¹ after rape or potatoes could be applied. The results demonstrated that barley of acceptable quality for malting can be grown after a break crop, providing that the rate of N fertiliser is suitably adjusted to take account of the residual fertility, but the results do not suggest that residual soil N affects the grain N concentration differently to N applied as fertiliser early in the season.     

Optimising flax production in the South Atlantic region of the USA

Worldwide the USA is the largest user of flax fibre, though very little is actually grown or produced in the USA. ‘Ariane’ flax was grown in 1990–1991, 1991–1992 and 1998–1999 in South Carolina, USA and evaluated for production characteristics. Plots (15 m long and 2 m wide) in the fall of 1990 and 1991 generated dry matter plant yields ranging from 4510 (early harvest at a seeding rate of 67 kg ha^?1) to 7340 (late harvest at a seeding rate of 134 kg ha^?1) kg ha^?1. Based on these results, seed was sown on a private farm using a drill in 19 cm rows at a seeding rate of 101 kg ha^?1 in 1998–1999. Early harvest, selected for optimal fibre quality, produced a dry matter plant yield that averaged 4076 kg ha^?1. Late harvest, selected to optimise seed plus fibre, produced a dry matter plant yield that averaged 5076 kg ha^?1. Stubble remaining in the field after mowing at about 6.0–7.6 cm above the soil surface resulted in a fibre loss of about 3% of total plant dry matter or 10% of potential total fibre yield. Dry matter and fibre yields suggested that flax could be produced in the southeastern USA using traditional farming methods for the area. Copyright © 2004 Society of Chemical Industry     

The effect of harvest date on the yield and composition of Tasmanian dill oil (Anethum graveolens L.)

Semi-commercial plots of dill (Anethum graveolens L.) were established in the Derwent Valley area of Tasmania during 1981 and 1982. The 1981 crop was irrigated and yielded 43 to 104 kg ha^?1 of dill herb oil (less than 35% carvone) or 57 to 73 kg of dill seed oil ha^?1, depending on harvest date. The non-irrigated crop established in 1982 yielded 41 to 77 kg of dill herb oil. The carvone content of oil from the 1982 crop failed to reach a level of 35%, the minimum considered characteristic of dill seed oil. These results indicate that Tasmania is well suited to the production of either dill herb or seed oil and that higher yields of oil and carvone are obtained per hectare from the herb crop. Major components of Tasmanian dill oil were carvone (9.6 to 46.5%), α-phellandrene (15.5 to 49.1%), β-phellandrene (5.2 to 7.6%), limonene (16.5 to 22.3%) and dimethylhexahydrobenzofuran (0.4 to 11.9%).     

Effect of drought and irrigation on the fate of nitrogen applied to cut permanent grass swards in lysimeters: Nitrogen balance sheet and the effect of sward destruction and ploughing on nitrogen mineralisation

Fuor years after ¹⁵N labelled fertiliser nitrogen (as Ca(NO₃)₂ and equivalent to 400 kg N ha^?1) was applied to permanent grass swards growing in lysimeter monoliths, approximately one-quarter remained immobilised in soil organic matter. In the intervening years similar but non-labelled applications were made. Although differing rainfall regimes applied during the experiment had significantly affected nitrogen uptake by plants and nitrate loss in drainage, they caused no significant effect on the tracer nitrogen remaining in the soil, the ranges were 85–97 kg N ha^?1 and 79–94 kg N ha^?1 respectively for the 135 cm deep clay and silt loam soil monoliths. Labelled nitrogen unaccounted for in crop, drainage or soil was presumed to have been denitrified. These losses averaged 62 and 49 kg N ha^?1 on the clay and silt loam soils respectively; again the differing rainfall regimes caused no significant differences. The ratio between estimates of labelled nitrogen denitrified and of annual nitroux oxide loss was approximately 9:1 for both soils. The conversion from permanent grass to winter wheat in autumn 1981, involving killing and then burying the sward, resulted in no pronounced increase in net mineralisation of labelled nitrogen. However, the balance between crop uptake and the quantity leached did change. Labelled nitrogen assimilated was less for the wheat (growing without addition of fertiliser nitrogen) than for the grass in its last year, and the quantity leached was considerably greater than under grass swards that were supplied with an average rainfall distribution. Following the first wheat harvest total nitrogen leached averaged 51 and 44 kg N ha^?1 on the clay and silt loam soils respectively. Rates of nitrous oxide emissions during the autumn following sward destruction were greater than in earlier years, but this enhanced loss was of short duration. The crop clearly benefited from the succession of nitrogen applications made to grass, as grain yield and total nitrogen uptake exceeded 7 t ha^?1 and 120 kg N ha^?1 respectively on both soils. These quantities exceed the national averages for winter wheat and are also considerably greater than for crops from lysimeters which received no nitrogen fertiliser throughout the experiment.     

Fertiliser requirements of spring oilseed rape

Because of the increasing importance of oilseed rape in the United Kingdom, 26 field experiments were done on the fertiliser requirements of the spring-sown crop in the years 1973 to 1975. Seed and oil yield were increased by nitrogen in 23 of the 26 experiments, though oil content was reduced somewhat. On average, the crop required 187 kg/ha of N for optimum yield and there was little difference in yield between seedbed and split N applications. Response to P was small on average, varied between years and was not well correlated with soil analysis; a 2 tonne/ha crop removes about 32 kg/ha P₂O₅. Mean response to K was very small and a 2 tonne/ha crop removes about 15 kg/ha K₂O; spring oilseed rape appears to require no applied K, except perhaps on soils of low K status. The crop did not respond at all to application of S.     

Quality of white cabbage yield and potential risk of ground water nitrogen pollution,as affected by nitrogen fertilisation and irrigation practices

BACKGROUND: The effect of different fertilisation (broadcast solid NPK application and fertigation with water‐soluble fertiliser) and irrigation practices (sprinkler and drip irrigation) on yield, the nitrate content in cabbage (Brassica oleracea var. capitata L.) and the cabbage N uptake was detected, in order to assess the potential risk for N losses, by cultivation on sandy–loam soil. The N rate applied on the plots was 200 kg N ha^?1. RESULTS: The highest yield (93 t ha^?1) and nitrate content (1256 mg kg^?1 DW) were found with treatments using broadcast fertilisation and sprinkler irrigation. On those plots the negative N balance (?30 kg N ha^?1) was recorded, which comes mainly from the highest crop N uptake (234 kg N ha^?1) indicating the lowest potential for N losses. CONCLUSION: In terms of yield quality and the potential risk for N losses, broadcast fertilisation combined with sprinkler irrigation proved to be the most effective combination among the tested practices under the given experimental conditions. The importance of adequate irrigation is also evident, namely in plots on which 50% drip irrigation was applied, the lowest yield was detected and according to the positive N balance, a higher potential for N losses is expected. Copyright © 2011 Society of Chemical Industry     

The fertiliser nitrogen requirement of cereals grown on sandy soils

The responses to fertiliser‐N of winter wheat and winter barley grown on sandy soils were measured in 72 experiments in England from 1990 to 1994. Yield without fertiliser‐N (Y₀) was c 1.1 t ha⁻¹ greater following root crops than following cereals. Following potato crops given organic manures, Y₀ was c 1.2 t ha⁻¹ greater than following unmanured potato crops, but Y₀ was no greater following sugarbeet to which organic manures had been applied. Only after the two driest winters was there sufficient variation in soil N supply in spring (SNS_s) for this to show a relationship with Y₀. However, Y₀ increased with increasing N mineralisation during the growing season (AM) in the three years it was measured. There was no consistent effect of sowing date on Y₀. Following potatoes, yield at optimum fertiliser‐N (Y_opt) decreased as sowing date was delayed, but this was not so after cereals, sugarbeet or overall. There was no increase in Y_opt with SNS_S or AM, but Y_opt decreased with increasing moisture stress (S) in June. The mean yield response to N_opt (Δ_Y) was c 0.4 and 0.8 t ha⁻¹ smaller following potatoes and sugarbeet respectively than following cereals, but not consistently so as there were large interactions between site, year and previous crop. Following root crops, Δ_Y was c 0.6 and 1.4 t ha⁻¹ less after sugarbeet and potatoes respectively that had been given organic manures. Without the addition of organic manures, Δ_Y following potatoes was similar to that following cereals. Regression on SNS_S and AM accounted for 28 and 15% respectively of the variance in Δ_Y. The optimum economic fertiliser‐N application (N_opt) was similar, at c 140 kg ha⁻¹, following cereals and potatoes. Following sugarbeet, cereal N_opt was only c 110 kg ha⁻¹. The differences according to previous crop reported here are consistent with mineralisation of crop residues on sandy soils being more rapid than on other soils; the potato residues were rapidly mineralised in autumn and lost by leaching over winter. Residues from later‐harvested sugarbeet were mineralised during the growing season of the subsequent cereal crop. Fertiliser‐N requirements were, at c 110–140 kg ha⁻¹, smaller than has been found on other soil types, and less than current recommendations for wheat. Requirements were significantly reduced in years of drought stress. No differences were found in N_opt between wheat and barley. These data do not justify the current advice to invariably reduce fertiliser‐N to cereals following potatoes by 20–25 kg ha⁻¹ on these sandy soils. On average a reduction of c 20 kg ha⁻¹ could be made following sugarbeet, with a further reduction of c 40 kg ha⁻¹ N if manures had been applied to the previous sugarbeet crop. A reduction of 40 kg ha⁻¹ N could also be made where cereals followed a potato crop to which manures had been applied. Further refinements on the basis of measurements of soil mineral N could not be justified. Seasonal variation in N response due to drought stress makes recommendations difficult on these soils. Adopting the fertiliser‐N recommendations proposed here would produce N surpluses to the soil of c 37, 10 and 27 kg ha⁻¹ respectively following cereals, sugarbeet and potatoes when cereal grain is removed but straw incorporated. On farms where straw is removed, N surplus would be largely eliminated. Our recommendation that no reduction in fertiliser‐N application to cereal crops grown on sandy soils should be made following potatoes will not increase fertiliser‐N use and is not expected to increase nitrate leaching. Some reduction in nitrate leaching may be achieved if recommendations following cereal crops and sugarbeet are made in accordance with the results reported here. © 2000 Society of Chemical Industry