NO3 dynamics in the soil, yield formation and N uptake of winter wheat as influenced by dosage and distribution effects of N‐fertilizer application In a 4 year series of field trials carried out with 9 regimes of nitrogen fertilizer application at two trial sites with rather shallow top soil layers but large deviations in soil characteristics, grain yield varied between 50 dt/ ha and 120 dt/ha with nitrogen doses from 0–170 kg N/ha. Soil nitrogen supply for wheat grain formation on unfertilized plots reached 80 kg N/ha/year within the narrow range of 75–95 kg N/ha in different years at both sites which amounts to 1.5 % and 0.5 % of the highly different N‐content of the trial sites. The most successful nitrogen application regimes are characterized by modest fertilizer doses in early spring and the delay of supplemental fertilizer doses until growth stage EC 32. They resulted into modest NO) soil content from EC 29 to EC 32 and/or a noticable decrease of soil NO3 content during growth stage EC 30–32, which seems to be responsible for the development of only modest stand densities and reduced straw yield, while the delayed supplementation with nitrogen fertilizer overcompensated these effects mainly by increased grain numbers/ear and a remarkable improvement of harvest index. The contribution of soil borne nitrogen to kernel yield formation started to decrease with even low dosages of supplemental nitrogen fertilization with the exception of the highest yielding season 1987/88. Top levels of grain yield have been regularly obtained with supplemental nitrogen fertilizer dosages about 40 kg N/ha below grain yield nitrogen extraction if they were added within favorable application regimes.

NO3 dynamics in the soil, yield formation and N uptake of winter wheat as influenced by dosage and distribution effects of N‐fertilizer application In a 4 year series of field trials carried out with 9 regimes of nitrogen fertilizer application at two trial sites with rather shallow top soil layers but large deviations in soil characteristics, grain yield varied between 50 dt/ ha and 120 dt/ha with nitrogen doses from 0–170 kg N/ha. Soil nitrogen supply for wheat grain formation on unfertilized plots reached 80 kg N/ha/year within the narrow range of 75–95 kg N/ha in different years at both sites which amounts to 1.5 % and 0.5 % of the highly different N‐content of the trial sites. The most successful nitrogen application regimes are characterized by modest fertilizer doses in early spring and the delay of supplemental fertilizer doses until growth stage EC 32. They resulted into modest NO3 soil content from EC 29 to EC 32 and/or a noticable decrease of soil NO3 content during growth stage EC 30–32, which seems to be responsible for the development of only modest stand densities and reduced straw yield, while the delayed supplementation with nitrogen fertilizer overcompensated these effects mainly by increased grain numbers/ear and a remarkable improvement of harvest index. The contribution of soil borne nitrogen to kernel yield formation started to decrease with even low dosages of supplemental nitrogen fertilization with the exception of the highest yielding season 1987/88. Top levels of grain yield have been regularly obtained with supplemental nitrogen fertilizer dosages about 40 kg N/ha below grain yield nitrogen extraction if they were added within favorable application regimes. Zusammenfassung 1. Die Kornerträge eines vierjährigen N‐Dün‐gungsversuches zu Winterweizen, der auf 2 flachgründigen Standorten mit stark unter‐schiedlichen Bodeneigenschaften durchge‐führt wurde, differierten bei Düngergaben zwischen 0–170 kg N/ha im Schwan‐kungsbereich zwischen 50 und 120 dt/ha. 2. Bei verhaltener Anfangsdüngung in Ver‐bindung mit einer verzögerten Erganzungs‐düngung wurden regelmäßig Höchsterträge erzielt. Sie wurden bei einem NO3‐Gehalt der Ackerkrume im Bereich von 20 bis 50 kg N/ha, im Entwicklungsabschnitt EC 29 bis EC 32 und/oder einer deutlichen Verarmung des NO3‐Gehaltes im Boden vor Anwendung ergänzender Düngungs‐maßnahmen im Stadium EC 32 durch eine geringere Zahl ährentragender Halme in Verbindung mit einer überkompensieren‐den Steigerung des Ährenertrages und ver‐bessertem Ertragsindex ermöglicht. 3. Im Vergleich der beiden Versuchsstandorte zeigte sich, daß trotz hoher Nt‐Vorräte der anmoorigen Auenrendzina deren weites C: N‐Verhältnis eine rasche Immobilisie‐rung des mineralisierten Stickstoffs begün‐stigte. Daher war eine stärkere Aufteilung der ergänzenden Düngergaben erforder‐lich, um eine optimale Versorgung der Weizenpflanzen auf diesem Boden sicher‐zustellen. 4. Trotz großer Unterschiede im Witterungs‐ablauf der Versuchsjahre und erheblicher Differenzierung der Nt‐Vorräte beider Stando...

Investigations on supplemental N‐fertilizer application for the optimum course of N‐uptake into winter wheat stands During a period of 5 years 14 N‐fertilization field trials with winter wheat have been carried out in which N‐uptake and biomass production in 6 growth stages were analysed. By comparison with non‐optimal variants of N‐supply a critical range for N‐uptake has been recognized which centered around an optimum value of 86 kg biomass N/ha at growth stage EC32. In connection with intensified N‐uptake during later growth stages, this has allowed full exploitation of the wheat yield potential without substantial decrease of the N‐harvest index. Field trials on two different soil types (Parabraunerde and humose Auenrendzina), different dates of sowing and long year stands in wheat monoculture as well as applications of N‐fertilizers containing dicyandiamid for delay of nitrification showed differences in efficiency as related to the fertilizer dosages but no systematic deviation from the optimum course of N‐uptake for full exploitation of yield potential. Provided that excessive fertilizer dosages before EC32 had been avoided, it seems possible to adjust the reuptake of winter wheat stands close to its optimum within an error of not more than 30 kg fertilizer N/ha by growth stage oriented splittings of fertilizer application and adequate account of soil‐N supply and weather conditions during early growth stages. Full exploitation of the wheat yield potential has been possible in all trials without significant losses in N‐use efficiency if optimal splittings and dosages of supplemental N‐fertilizers were provided.

Zusammenfassung In einem Versuch mit 63 Altsauen in 4 Gruppen wurde während einer gesamten Trächtigkeit untersucht, inwieweit die Höhe der Energieversorgung (21,7 und 26,5 MJ ME/Tag) sowie eine einmalige Anhebung der Energiezufuhr am 85. Trächtigkeitstag von 19,6 bzw. 24,3 MJ ME/Tag auf 27,9 bzw. 32,6 MJ ME/Tag Einflüsse auf die Wurfgröße sowie das Gewicht von Sauen und Ferkeln bei der Geburt ausüben können. Die Gewichtszunahmen der graviden Sauen wurden signifikant von der Höhe der Energiezufuhr beeinflußt, die sich auch in einem signifikant unterschiedlichen, extrauterinen Gewichtszuwachs widerspiegelten. Die Staffelung der Energie hatte dabei insgesamt keinen Einfluß. Weder die Trächtigkeitsdauer noch die Zahl der gesamt bzw. lebend‐ und totgeborenen Ferkel war durch Energieversorgung und/oder ‐verteilung in der Gravidität signifikant beeinflußt. Auch beim Wurfgewicht sowie bei den Geburtsgewichten der Ferkel war mit höherer Energiezufuhr kein signifikanter Anstieg zu beobachten.

Long term studies on the effects of the level of energy supply during gestation on changes of bodyweight and reproductive performance in the sowA trial with 21 sows investigated over two consecutive reproduction cycles to determine whether the level of energy intake during pregnancy (21.7 or 26.5 MJ ME/day) has an influence on the size of litter and on the body weight of sows and piglets at parturition and during lactation was carried out.In the second reproductive cycle some negative effects of the continuosly low level of energy supply became evident. The number of abortions and stillbirths increased and the weights of litters and single piglets were reduced at parturition and at weaning. However, there were lower losses of piglets during lactation. The level of energy supply during pregnancy had only a negligible influence on the body weight of the sows during gestation. During lactation there were no effects. The feed intake of the lactating sows did not depend on the energy supply during pregnancy.