Riktig tilførsel av nitrogen og svovel om høsten for bedre vinteroverlevelse av flerårig gras, med vekt på gras til grøntanlegg

Winter injuries on grassland give considerable economic losses and negative environmental consequences as nutrient losses and energy consumption. The aim of this project was to examine the effects of autumn fertilization on grass? winter stress tolerance and to update the guidelines for grass growers. In 2014 and 2015 three USGA greens were established with creeping bent (Agrostis stolonifera) and annual meadow grass (Poa annua). One of the experiments was conducted on the lysimeter facility at NIBIO Landvik. The other green was at NIBO Apelsvoll. During the acclimation period, half the green was shaded to about 70% of full sunlight. From the end of August until the end of November the greens were fertilized weekly with liquid, complete, balanced fertilizers. Only the nitrogen and sulphate content varied between the treatments. The application rate declined weekly. The total N rates in the experimental period were 0 / 2.8 / 5.6 /8.5 g/m2. The 5.6 g /m2 rate was also combined with either excessive rate of sulphate (N:S = 1:1.6) or no sulphate. Grass plants from the experimental greens were sampled in November/December and at the end of February and tested in the laboratory for freezing tolerance, resistance to pink snow mould and suffocation. Some results Nitrogen leakage On average for two autumns, 40 % of the high N and 20% of the middle N rate leached through the drain. Drain water was collected and analysed every two weeks. The highest nitrate concentration found was 14 mg/l. Leaching from zero N plots was on average 0.5 g N /m2 and higher in the relatively dry autumn 2015 than in the wet 2014. Shade effects The green in shade had significantly more disease and the average freezing tolerance (LT50 value) was bad compared to the plants exposed to full daylight. Shade strongly reduced the tiller density and survival in the field. We did not find negative effects of shade on the tolerance to anoxia when Microdochium nivale was controlled sufficiency in the autumn. Excessive sulphate High rates of sulphate did not reduce damages from Microdochium nivale in field nor in laboratory tests. Nitrogen rates in the autumn High rates of nitrogen significantly increased the severity of microdochium diseases in annual meadow grass and made creeping bent more vulnerable to pink snow mould. Freezing tests showed that annual meadow grass was not significantly affected by the autumn fertilization. In creeping bent there was a strong negative correlation between nitrogen rates and LT50 values. Colour and growth Nitrogen rates had a significant impact on height growth in the autumn. The zero N plots did not have acceptable autumn colour and the growth was negligible. The highest N-rate gave the best spring colour for creeping bent and medium N-rate gave the best colour for annual meadow grass. Spring growth could not be predicted by the grass colour. Medium and high N-rates both gave good spring growth in creeping bent. The low N application gave best spring growth in annual meadow grass. Full scale experiments Five golf courses tested out the effects of autumn application of nitrogen during the winter season 2016/17. The experiment confirmed some of the results presented above. New guidelines As concluding document, a handbook, ?Winter stress management of turf grass?, with detailed practical guidelines, and the results, was finalized, presented and discussed at the international seminar Winter Stress Management for Golf Courses in Oslo/Gardermoen 9-10 November 2017.

Genetisk sterke planter og god herding (styrt av lys og temperatur) om høsten er en forutsetning for vinteroverlevelse av flerårige grasarter. Nye norske forsøk har vist at høstgjødsling med nitrogen gir mindre vinterskader, men optimale tidspunkt og meng der er ikke bestemt. Fra andre vekster er det kjent at gjødsel med svovel kan gi mindre soppskader, men vi vet lite om hvordan dette påvirker snømugg. Det vil bli anlagt to feltforsøk på golfgreener der ulike mengder nitrogen og svovel tilføres artene k rypkvein og tunrapp om høsten. Gjødsel tilføres ukentlig i perioden da forventet dagtemperatur synker fra 12 til 1 °C. Et av forsøkene legges til lysimeteranlegget på Bioforsk Landvik for å måle utlekking av nitrogen. Det andre forsøket, på Bioforsk Apels voll, skal også sammenligne gras i sol og skygge. Fra feltforsøkene tas inn prøver til laboratorietester for å måle spesifikk resistens mot frost, kvelning (isbrann) og rosa snømugg (under kunstig snødekke). Det er ventet å finne et optimalt nitrogennivå som kan knyttes til gressart, sted og lysforhold. Svovel forventes å være viktig for plantenes sykdomsresistens. Et høyt kompetent kanadisk institutt vil analysere innholdet av ulike karbohydrater og se etter en sammenheng mellom høstgjødsling, overvintri ng og fruktaner. Resultatene vil bli brakt til næringen gjennom storskalaforsøk på golfbaner i Norge og de andre nordiske land der de viktigste effektene fra småskalaforsøkene vil bli demonstrert. På disse banene skal det også arrangeres feltdager som og så skal gi bildemateriale til populærvitenskaplige artikler og videosnutter. I tillegg til 3-4 vitenskaplige artikler vil det bli skrevet en håndbok i vinterskjøtsel av gras til grøntanlegg. Denne vil bli presentert på et nordisk seminar om vinteroverleve lse høsten 2017. Prosjektet eies av Norges Golfforbund, andre organisasjoner som arbeider med golfbaner og deres fellesnordiske forskningsstiftelse STERF. Faglig ledelse har Bioforsk Turfgrass Research Group.