Simple soil carbon model for use in the HighCrop decision model

The soil carbon turnover model used in the HighCrop decision support model is described

Hvordan kan udvaskningen og belastningen af vandmiljøet yderligere reduceres?

Kvælstofudvaskningen bestemmes i højere grad af afgrødedække om efteråret end af hvor meget gødning, der gives

Kvælstofforsyningen på økologiske planteavlsbedrifter

Med udfasning af import af konventionel husdyrgødning bliver det nødvendigt med et større fokus på kvælstoffikserende afgrøder i økologiske planteavlssædskifter

Fødevarernes andel af klimabelastningen

Produktion og forbrug af fødevarer er ansvarlig for et betydeligt bidrag til de globale udslip af driv-husgasser. Udslippene skyldes direkte udledninger af drivhusgasserne metan (CH4) og lattergas (N2O) i forbindelse med produktionen. Disse drivhusgasser har henholdsvis 21 og 310 gange krafti-gere drivhuseffekt end CO2. Drøvtyggernes fordøjelse er den største enkeltkilde til metan udled-ning, desuden kommer der metan fra gødningslagrene. Lattergas dannes, når kvælstof omdannes ved mikrobielle processer i jorden. Derfor øges udslippet af lattergas, når jorden tilføres kvælstof-gødninger. Landbruget har endvidere et energiforbrug (direkte og indirekte), som også bidrager til udledning af CO2

Cereal yield and quality as affected by N availability in organic and conventional crop rotations in Denmark: a combined modeling and experimental approach

The effects of nitrogen (N) availability related to fertilizer type, catch crop management, and rotation composition on cereal yield and grain N were investigated in four organic and one conventional cropping systems in Denmark using the FASSET model. The four-year rotation studied was: spring barley–(faba bean or grass-clover)– potato–winter wheat. Experiments were done at three locations representative of the different soil types and climatic conditions in Denmark. The three organic systems that included faba bean as the N fixing crop comprised a system with manure (stored pig slurry) and undersowing catch crops (OF+C+M), a system with manure but without undersowing catch crops (OF−C + M), and a system without manure and with catch crops (OF + C−M). A grass-clover green manure was used asNfixing crop in the other organic system with catch crops (OG+C+M). Cuttings of grass-clover were removed from the plots and an equivalent amount of total-N in pig slurry was applied to the cropping system. The conventional rotation included mineral fertilizer and catch crops (CF+C+F), although only non-legume catch crops were used. Measurements of cereal dry matter (DM) at harvest and of grain N contents were done in all plots. On average the FASSET model was able to predict the yield and grain N of cereals with a reasonable accuracy for the range of cropping systems and soil types studied, having a particularly good performance on winter wheat. Cereal yields were better on the more loamy soil. DM yield and grain N content were mainly influenced by the type and amount of fertilizer-N at all three locations. Although a catch crop benefit in terms of yield and grain N was observed in most of the cases, a limited N availability affected the cereal production in the four organic systems. Scenario analyses conducted with the FASSET model indicated the possibility of increasing N fertilization without significantly affecting N leaching if there is an adequate catch crop management. This would also improve yields of cereal production of organic farming in Denmark

The role of catch crops in the ecological intensification of spring cereals in organic farming under Nordic climate

The contribution of catch crops to the ecological intensification of organic arable systems was investigated using data of a 12-year field experiment carried out at three sites in Denmark. This study focused on the yields of spring oats and spring barley in systems with and without manure in two different cropping systems that differed in the proportion of legume-based catch crops (O2 lower and O4 higher) and in the rotation composition (grass-clover green manure in O2 and pulse crops in O4). Three consecutive four-year crop rotations were established at three locations representative of the different soil types (loamy sand, sandy loam and coarse sand) and climatic conditions. Crop management and soil operations were performed following common practices in organic farming. Measurements of dry matter (DM) and nitrogen (N) content of grain cereals at harvest, aboveground biomass in catch crops and green manure crops in autumn and of the green manure crop at the first cutting were performed. The effect of catch crops on grain yield varied with cereal and catch crop species, soil and rotation type, and the application of N in manure. Higher yield increases from previous catch crops were obtained for spring oat than for spring barley with mean estimates of the apparent N recovery efficiency of 69% and 46%, respectively. However, lower autumn N in undersown crops with higher cash crop yields was also observed. For spring oats mean grain yield benefits of including catch crops varied from 0.2 to 2.4 Mg DM ha-1 31 depending on location, manure use and course of the rotation. In spring barley mean grain yield benefits from catch crops varied from 0.1 an 1.5 Mg DM ha-132 . There was a tendency for the effect of catch crop on grain yield to increase over time. These results indicate that in Nordic climates catch crops can contribute to the ecological intensification of spring cereals, not only by reducing the nitrate leaching and increasing N retention, but also by improving yields. Management practices in relation to catch crops must be adapted to the specific soil and cropping systems

Økologisk planteavl kan lagre kulstof

Mere kulstof i jorden er ikke kun gavnligt for klimaet. Det kan også være med til at forbedre jordens frugtbarhed

Højere udbytter ved rækkedyrkning og efterafgrøder - RowCrop

Den største udfordring for at opnå højere og mere stabile udbytter i økologisk planteavl er knyttet til tilstrækkelig N-forsyning og bekæmpelse af aggressivt ukrudt. RowCrop udviklede, evaluerede og demonstrerede et nyt rækkedyrkningssystem, der udnytter den seneste udvikling inden for vision og GPS-styrede rækkedyrkningsudstyr ved effektivt at integrere traditionelle landbrugsafgrøder med rækkedyrkning af efterafgrøder og målrettet ukrudtsbekæmpelse. RowCrop udviklede det videnskabelige grundlag for forbedret kontrol af aggressive en- og flerårige ukrudtsarter i et rækkedyrkningssystem og for dyrkning af mere produktive N-fikserende efterafgrøder til øget N-forsyning af afgrøderne. Projektet skulle dokumentere effekter af dyrkningssystemet på produktivitet, ukrudtsbestand, N-forsyning, N-udvaskning og kulstoflagring i et langvarigt sædskifteforsøg ved forskellige inputniveauer i økologisk planteavl. Projektet demonstrerede og formidlede desuden resultaterne til rådgivere og landmænd gennem markforsøg, åbent hus-arrangementer, workshops mv. De forventede årlige effekter var: Økonomi: Øgede udbytter i økologisk kornavl på 1,2 ton/ha (100 mio. DKK). Miljø: Reduceret nitratudvaskning på 10 kg N/ha (500 ton N). Klima: Øget kulstoflagring i jorden på 200 kg C/ha (37,000 ton CO2). Desuden forventedes resultaterne at bane vej for udfasning af import af konventionel husdyrgødning i økologisk jordbrug og for en øget omlægning fra konventionel til økologisk jordbrug

Kvælstofudvaskning

Kvælstofudvaskningen bestemmes i højere grad af afgrødedække om efteråret end af hvor meget gødning, der gives

Organisk gødning udnyttes for dårligt

Der er stor variation i udnyttelsen af organisk gødning, men efterafgrøder og grøngødning har flere roller i sædskiftet