SUMMARYFour field experiments were conducted on wheat, using the bread-making cultivar Hereward, over 3 years to study the interactions between nitrogen (N) and strobilurin fungicides with respect to yield and grain N. In one of the field experiments, above-ground dry matter (DM) yield was greater when the plots were treated with a mixture of triazole and strobilurin than when either no fungicide or triazole alone was applied. On plots that received no N fertilizer, above-ground DM and grain yield were lower for the plots treated with fungicides than for plots not treated with fungicide, which implied that the benefit of applying fungicides could only be exploited with N fertilization. There was no difference in above-ground N accumulation between fungicide programmes; however, greater N accumulation in grains was observed following the application of a mixture of triazole and the strobilurin trifloxystrobin compared with plots treated with either no fungicide or triazole alone. This increase in grain N appeared to be attributable more to improved translocation of N to grains rather than to increased N uptake from the soil. The two strobilurin fungicide ingredients kresoxim-methyl and trifloxystrobin, each mixed with a triazole and tested in the present study, performed differently. Better performance, especially with respect to grain N yield, was observed most frequently with trifloxystrobin compared to kresoxim-methyl.

SUMMARYFour field experiments were conducted over 3 years to study whether adding a strobilurin fungicide to a triazole fungicide programme for disease control in winter wheat had any influence, in combination with different rates of fertilizer nitrogen (N), on the severity of foliar diseases, the degree of leaf senescence and consequently on yield.Septoria triticiwas the dominant foliar disease observed in all experiments. The area under the disease progress curve (AUDPC) tended to be greater for untreated plots than those treated with fungicides; however, the performance of the programme containing a strobilurin fungicide did not always exceed that of the triazole-only programme. Fitting a quadratic equation to relationships between leaf N concentration and the proportion of leaf area covered withS. triticion a relative scale across the four experiments indicated a possibility that there could be an optimum N concentration in host plants forS. triticito develop, rather than a simple increase or decrease with a rise in plant N concentration. Plant height tended to be reduced following an application of a mixture of epoxiconazole and trifloxystrobin; however, it was not clear whether there was any association between plant height and the severity ofS. tritici. S. triticicaused a reduction in mean grain weight (MGW) in most of the experiments. It was concluded that an optimum leaf N concentration may exist forS. triticiin winter wheat.

In Japan a high dependency on imported food, particularly livestock feed, has resulted in the accumulation of large amounts of nutrients, especially nitrogen, in the form of livestock manure. Cultivating feed crops that can take up a large amount of N would not only mitigate the water pollution caused by the nitrate leached from the livestock sector, but would also improve food self sufficiency. Sugarcane (Saccharum spp.) is considered to be a promising candidate in this respect. Two field experiments were conducted in 2006 and 2007 in Kagawa to evaluate the dry matter (DM) yield, N content and nitrate‐N concentration of sugarcane under high N input. The first experiment was designed as a factorial experiment with two factors, varieties/lines/clones and N rates set at two levels, 30 g m−2 year−1 and 60 g m−1 year−1, with three replicates. In the second experiment, 30 varieties/lines/clones of sugarcane and related genera as well as control crops were planted (n = 2) and a single N rate of 45 g m−2 year−1 was applied. Some varieties/lines of sugarcane produced an above‐ground DM yield greater than 4.0 kg m−2 and contained more than 40 g m−2 of N in the above‐ground part. Erianthus clones, IK76‐126 and IJ76‐349 tended to accumulate nitrate‐N when high rates of N were applied. No sugarcane varieties out of the 28 varieties/lines tested in the present study accumulated nitrate‐N beyond the allowed limit for feed use, irrespective of the N rates tested in the experiments. The ability of sugarcane not to accumulate nitrate‐N under conditions of high N input was considered to be an advantage in double‐purpose cultivation; that is, sugarcane can be used as a feed and cleaning crop.

Many kinds of sugarcane hybrids and relatives were planted in two sites, Tsukuba and Nasushiobara, in the northern Kanto region of Japan to evaluate their overwintering ability and biomass production. JW49 (Saccharum spontaneum L.), US56-15-2 (S. spontaneum L.) and Ponape Hurukimura (Saccharum barberi Jeswiet) were able to overwinter in the field experiment conducted in Tsukuba, but not in Nasushiobara. In the field experiment conducted in Nasushiobara, only two lines, JW599 (Saccharum spontaneum L.) and JW630 (Erianthus spp.), overwintered. JW630 also showed good ratooning ability in Tsukuba, even though the results were obtained from the experiment without replication. The newly planted JW599 and JW630 were small in the first year, but from the second year the biomass production of the ratoon plants became huge. The dry matter yields of JW599 and JW630 in the first year were 0.07 and 0.13 kg per hill, respectively, and the average dry matter yields of JW599 and JW630 during three years of ratoon cultivation were 1.46 and 2.63 kg per hill per year, respectively. Assuming that they are planted at 1.5-m inter-row intervals and 0.3 m inter-hill intervals, and each hill can accumulate the same dry matter yield, the dry matter production of the ratoon plant of JW599 and JW630 is estimated to be 32.5 and 58.4 t/ha, respectively.