SummarySoil NO3-N and NH4-N were measured to 90 cm depth in autumn and again in spring, under several sets of winter wheat experiments, on contrasting sites. Crop samples were taken throughout the growing season, both before and after the fertilizer N was applied, to measure N uptake. The amount of NO3-N in soil at the outset of growth in autumn was related to the uptake of N by wheat not given any fertilizer N until April.The effect of sowing date (September v. October) on both crop and soil N was compared, as also was the effect of soil type (retentive of NO3-N v. readily leached) and previous crop (potatoes v. oats and wheat v. beans).The amounts of NO3-N in the soils in autumn related well with previous crop and declined gradually during winter on the heavier soils, but rapidly on the sandy soil, in the latter case as a consequence of leaching. On the heavier soils, where little leaching occurred, the decline in soil NO3-N related well with the amount of N taken up by September-sown wheat during autumn and winter, but not with that taken up by October-sown wheat, where NO3-N accumulated in the soil during winter, because uptake was so small. Hence delayed sowing enhanced the likelihood of losses of NO3-N by leaching or by denitrification. On the sandy soil at Woburn, whilst the September-sown wheat removed more N than the October-sown, losses of NO3-N by leaching were severe, so that late winter growth was restricted by shortage of N in soil, and the amount of N taken up was far smaller than at Rothamsted.The soil measurements distinguished between the NO3-N residues remaining after beans or wheat in the same field and between residues after oats or potatoes on soils of the same soil series, but in different fields on the same farm.The amount of NO3-N in soil and the N taken up by wheat in February-March were together used to adjust the amount of fertilizer N applied in April, using a balance sheet approach to meet a specific yield objective. Some of the N uptake data from these experiments are presented. This should aid the calculation of N requirement during specific growth periods and thus help improve the prediction of fertilizer N dressings in spring.

SummaryMultifactorial experiments on winter barley cv. Igri grown after potatoes were made from 1981 to 1983 on silty clay loam soils at Rothamsted. All tested combinations of seven factors, each at two levels: with and without autumn pesticide (aldicarb), two sowing dates (September or October), with and without a fungicidal seed treatment (‘Baytan’), with and without spring and summer fungicides, two amounts of nitrogen, two times of applying nitrogen and with and without a growth regulator (‘Terpal’). Growth, development, yield, nitrogen uptake, pests and diseases were monitored. Sowing in September, fungicide sprays in spring and summer, and the growth regulator had the largest mean benefits on grain yield (+0·80, +0·56 and +0·34 t/ha respectively). Some factors interacted with sowing date; thus aldicarb, the fungicide sprays in spring and summer and the later timing of N all increased yield more on the September-than on the October-sown barley. The larger yields on the September-sown plots were associated with more ears/m2 (978 v. 744) and, in spite of fewer grains per ear (17·8 v. 20·1), more grains per m2 (17·6 v. 14·7 × 103), but lighter grains (39·2 v. 42·3 mg). The largest yields each year (ca. 8.0–8.5 t/ha) were obtained from September-sown barley fully protected from pests and from pathogens in spring and summer and given N in April rather than in March.The aphid vectors of barley yellow dwarf virus were sufficiently common and infective in two of the three autumns to infect the September-sown barley sufficiently that their control by aldicar b enhanced yield. Nematodes, slugs and dipterous stem borers were not numerous enough to be damaging in any year. Mildew in autumn was controlled by the seed treatment, but effects on yield were inconsistent. Mildew in spring and summer was more abundant on the October-than on the September-sown barley; it was controlled by fungicide sprays, which increased yield significantly each year. Leaf blotch was more abundant on the September-sown barley.

AGS 105 98 F . V. WlDDOWSON AND OTHERS greatly by the sprays of aphicide and fungicides, was decreased by N, and was larger for Norman than for Avalon.In 1980-1, after beans, the mean amounts of N removed by the grain (where aphicide and fungicides were given) ranged from 81 kg/ha without N fertilizer to 167 where most N was given. In 1982-3 comparable values ranged from 86 kg N/ha to 191 where wheat followed beans and from 35 kg N/ha to 168 where wheat followed wheat.

The results of about ninety field experiments carried out over three years to test dicalcium phosphate, nitrophosphate, ammoniated fertilizer and Gafsa rock phosphate are summarized and discussed. Soils with pH values of 6·5 and below are listed as ‘acid’, those with higher pH values as ‘neutral’. All comparisons were made in terms of fertilizers supplying the same total amounts of phosphorus.Dicalcium phosphate dihydrate gave approximately the same yields as superphosphate for potatoes (both on acid and on neutral soils) and for grass, kale and barley. In one group of swede experiments mostly carried out in the north-east of the country dicalcium phosphate was inferior to superphosphate, but it was equal to superphosphate in another group of swede experiments, most of which were on acid soils in wetter areas.A nitrophosphate made in England on pilot-plant scale was consistently inferior to superphosphate for barley, potatoes and swedes.

An experiment at Saxmundham, Suffolk, during 1974-6, tested late sprays of a liquid N-fertilizer (ammonium nitrate/urea) supplying 50 kg N/ha, and a broad spectrum fungicide (benomyl and maneb with mancozeb) on winter wheat given, 0, 50, 100 or 150 kg N/ha as 'Nitro-Chalk' (ammonium nitrate/calcium carbonate) in spring.Mildew (Erysiphe graminis f. sp. tritici) was most severe in 1974. It was increased by N and decreased by the fungicide in both 1974 , but was negligible in 1976 was very slight in 1974 and none was observed in 1976. It was much more severe in 1975, but was unaffected by the fungicide perhaps because this was applied too late.Yield and N content, number of ears and leaf area index were determined during summer on samples taken from all plots given 100 or 150 kg N/ha in spring; each was larger with 150 than with 100 kg N/ha. The effects of the liquid N-fertilizer on yield and N content varied, but leaf area index was consistently increased. None was affected consistently by the fungicide.Yields, percentages of N in, and amounts of N removed by grain and straw were greatly and consistently increased by each increment of 'Nitro-Chalk'. Yields of grain were increased (average, 9 %) by the liquid fertilizer in 1974 and 1975, and most where most 'Nitro-Chalk' had been given, but not in 1976 when the wheat ripened in July; however, both the percentage of N in and the amount of N removed by the grain were increased by the liquid fertilizer each year. The fungicide increased the response to the liquid N-fertilizer in 1974, but not in 1975 when Septoria was not controlled, nor in 1976 when leaf diseases were virtually absent.The weight of 1000 grains was increased by each increment of 'Nitro-Chalk' in 1975 but only by the first one (50 kg N/ha) in 1974 and 1976; it was very slightly increased by the liquid fertilizer and by fungicide each year. l a t e s P r a V S o f a l i ( l u i d N-fertilizer and (ii) whether this extra N would increase yield and N content There has recently been much interest in increas-more if late developing leaf diseases were controlled ing the N content (and thus protein) of both by a broad spectrum fungicide. The experiment milling and feeding wheat grain by applying extra-was continued in 1975 and 1976. N-fertilizer, usually in liquid form, about the time Also, because during 1966-70 wheat grain yields of ear emergence. However, large amounts of N at Saxmundham had been smaller and more variapplied to cereals can increase foliar diseases able than those fiom wheat grown in comparable (Jenkyn, 1977) which, unless controlled, can situations at Rothamsted (Slope, Etheridge & decrease yields. An experiment, begun at Sax-Williams, 1973) we chose to compare the growth mundham in 1970 to test amounts of spring-and yield of wheat in this experiment with that applied 'Nitro-Chalk' for successive crops of winter grown on Broadbalk field at Rothamsted. The wheat (Williams & Cooke, 1972), was therefore variety grown (Cappelle-Desprez) and the premodified in 1974 to determine (i) whether yiel...

We present results from an experiment at Saxmundham measuring the effects of growing different numbers of successive winter wheat crops, each year, from 1971 to 1976; it followed five cropping sequences introduced from 1966 to 1970.From 1971 to 1973 four seed rates, two row spacings and three nitrogen rates were tested in all combinations with four of the previous cropping sequences. The remaining sequence was sown traditionally for continuity. Number of ears, leaf area, yield and nutrient content showed little benefit from increasing or decreasing seed rate, around that usually sown. Rows 15 cm apart gave the largest yield independently of N, because they produced most ears. There was no loss in yield from growing up to eight consecutive crops of winter wheat. 100 kg N/ha was sufficient for maximum yield.From 1974 to 1976 two varieties of different potential (Cappelle-Desprez and Maris Huntsman), chlormequat chloride (CCC), three amounts of N, as single, or as divided dressings, were tested in all combinations with the four cropping sequences. The fifth sequence again was sown traditionally, but with or without autumn-applied N. Maris Huntsman gave a grain yield only 0-22 t/ha larger (4-5%) than that of CappelleDesprez, and mean yields were larger (also by 4-5%) where CCC was given. Divided dressings of N increased yields by 0-11 t/ha (2-2%). The mean increase in yield from adopting all three improvements was 0-5 t/ha (or 11%). Yields of the 10th and 11th consecutive wheats declined, probably because black grass (Alopecurus myosuroides) became abundant. There was a good inverse relationship between losses of N in drainage during winter and subsequent yield and grain nitrogen uptake, which helped to explain large yield variations from year to year. TNTROTinOTTON t ' i e °^[ leT ^a^' which had been given uniform P and K manuring since 1952, was used for a crop sequence The sandy-clay loam (Beccles Series) at the experiment. Yields of continuous wheat (CappelleSaxmundham Field Station, Suffolk (founded in Desprez) were compared from 1968 to 1970 with 1899), which is typical of heavy land in the area, is those after phased-in tests (begun in 1966) of a 2-formed in Chalky Boulder Clay with surface layers year break of Italian ryegrass and beans. The containing much sand (Hodge, 1972). It is plastic purpose was to increase yields (by introducing the when wet, hard when dry and rarely friable. As break and increasing the amounts of N given in such it is better suited to autumn-sown than to spring) and to determine whether take-all (Gaeuspring-sown crops and, with adequate manuring, mannomyces graminis) and eyespot Pseudocercowinter wheat could be expected to yield well, sporella herpotrichoides) were as damaging to wheat However, in Rotation II (the site used for our grown after wheat as they are at Rothamsted (Slope, experiments) the largest mean from any treatment Etheridge & Williams, 1973). Yields were increased during 1900-52 was only 2-7 t grain/ha (Boyd & in the year after the 2-year break (to 4-34 compared Tris...

With Plate 11)Stiff-strawed varieties of winter wheat have been generally grown for some years, they give large and consistent increases in yield from generous nitrogen manuring. Previously the risk of lodging made it undesirable to apply heavy dressings of nitrogen but, with the newer varieties, this restriction does not apply on most soils, and it is possible for farmers to apply nitrogen freely up to the economic limit of the response. More recently stiff-strawed varieties of spring wheat and barley have been introduced, and heavier dressings of nitrogen may now be given to these crops. The purpose of the experiments described here was to measure the responses by modern varieties of spring wheat and barley to increasing dressings of nitrogen, and also to compare the yields given by alternative methods of application.Most farmers apply a compound fertilizer containing nitrogen, phosphorus and potassium for spring cereals, this may either be broadcast over the seedbed or combine-drilled with the seed. Most current compound fertilizers supply insufficient nitrogen to give a full crop on the poorer soils, unless excessive quantities of phosphorus and potassium are applied at the same time. In practice, rates of dressing are also limited by the output of the combine-drill and by the capacity of the fertilizer hopper. To overcome these practical limitations seedbed dressings have often to be supplemented with top-dressings of nitrogen after the crop has become established, this allows actual dressings to be adjusted to the fertility of individual fields and to the appearance and growth of the crop. Previous experimental work (Crowther, 1945) showed that combine-drilled dressings of phosphorus and potassium produced higher yields of cereals than equivalent broadcast dressings, but there is little experimental evidence on the relative values of drilling and broadcasting for nitrogen. These experiments compared ammonium sulphate combine-drilled with dressings broadcast over the seedbed immediately after sowing. In addition, comparisons were made between dressings of ammonium sulphate given at sowing and equivalent top-dressings of nitrogen as 'Nitro-Chalk' applied in mid-May. NATURE OF THE EXPERIMENTSSites for the fourteen experiments carried out over three seasons were selected on different kinds of soil in Bedfordshire and Hertfordshire. Spring wheat was grown on most of the heavy soils, but on the lighter land the experiments were on barley.In the 1954 experiments comparisons were made between equivalent combine-drilled and broadcast seedbed dressings of ammonium sulphate; in addition the response to combine-drilled superphosphate was measured at each centre by including a plot without N or P. The effect of a top-dressing of 4 cwt./aere of 'Nitro-Chalk' (0-6 cwt. N/acre) applied in mid-May was also examined. The main plot comparisons and the dressings/acre in the 1954 experiments were:(1) No nitrogen or phosphorus.(2) Superphosphate only.(3) Superphosphate + 0-25 cwt. N, as ammonium sulphate broadcast on seedbed.(...

In field experiments on vegetable crops dressings of appropriate fertilizers were placed 2 in. to the side of the seed and 2–3 in. below the soil surface, and compared with the same amounts of fertilizer broadcast and worked into the surface soil. The work was carried out on ordinary arable land carrying rotations which included vegetables.Placing fertilizer gave higher yields of cabbage, lettuce, beetroot, onions, broad beans, runner beans and maize, than broadcasting. Fertilizer, however applied, had no regular effect on the yield of french beans.Both placed and broadcast fertilizer were tested at two rates of dressing. On average of all experiments on each crop, placing fertilizer at the low rate gave higher yields than broadcasting at the high rate. Broadcast fertilizer had little effect on yields of runner beans and broad beans, while placed dressings gave marked increases.In two-thirds of all individual experiments placing gave higher yields than broadcasting, and in one-third of the experiments placement was significantly better than broadcasting. There were no instances of significantly higher yields from broadcasting as compared with placing.Placing fertilizer made most of the crops grow more rapidly in the early stages than broadcasting, this improvement being often reflected in earlier maturity. For cabbage, lettuce and runner beans the relative gains from placing, as compared with broadcasting fertilizer, were much higher at the first than at the second harvest.By drilling fertilizer beside the seed of vegetable crops grown on ordinary soils, it is possible to economize in the dressings needed. In addition, some crops having placed fertilizer may be ready for market earlier. These advantages may be very profitable where high-value crops are grown and will justify the purchase of special placement drills.A small series of field experiments on established Brussels sprouts and autumn-planted cabbages compared mid-season top-dressings of nitrogen fertilizer broadcast by hand over the whole soil surface, with dressings placed at one point beneath the surface and near to the plants. The dressings used had practically no effect on yields of Brussels sprouts. Top-dressings broadcast in spring increased yields appreciably in two experiments on cabbage, and at both centres placing gave lower yields than broadcasting.