Tillage in the growing season is ineffective as a tool of increased soil N mineralization

Soil tillage serves a number of purposes such as control of weeds, incorporation of crop residues and manures, and maintenance or improvement of soil mechanical properties, including seedbed preparations. As a side-effect, soil tillage may affect turnover of organic matter (OM) by changing the particle size and spatial distribution of crop and manure residues in soil and by increasing the intimacy of residue/soil contacts. By breaking soil structural elements, tillage may contribute further to N mineralization by exposing physically protected organic matter to microbial turnover. Therefore, adjusting the time, intensity and frequency of soil tillage operations may enable optimization of synchrony, defined as the matching through time of N availability and crop N demand. This idea was experimentally investigated in the present study

Jordløsning i vækstsæsonen øger ikke N mineraliseringenen

Jordbearbejdning foretages almindeligvis for at klargøre jorden til såning eller for at nedmulde planterester og gødning. Ligeledes kan jordbearbejdning finde sted både i og uden for vækstsæsonen i forbindelse med mekanisk ukrudtsbekæmpelse. Der er en udbredt opfattelse af, at ukrudtsbekæmpelse, foretaget fx ved radrensning af rækkeafgrøder i vækstsæsonen, også øger mineraliseringen af kvælstof. En øget kvælstofmineralisering formodes at finde sted som følge af, at den mekaniske bearbejdning bryder jordknolde, hvorved der blotlægges organisk materiale, som nedbrydes. Samtidigt fremmer jordbearbejdningen luftskiftet i jorden, og betingelserne for omsætning forventes dermed forbedrede. En øget kvælstofmineralisering som følge af jordbearbejdning ville åbne mulighed for at styre kvælstoffrigivelsen i forhold til en afgrødes vækst. Potentialet for dette er undersøgt i vinterhvede, hvor det blev testet, om jordløsning kunne gøre det ud for en sengødskning med kvælstof

Kerneudbytte af vårbygsorter og sortsblandinger under forskellige gødningsniveauer

Der var ikke signifikant forskel på kerneudbyttet af sortsblandingen og gennemsnittet af de tre sorter, som indgik i blandingen. Anvendelse af sortsblandinger kan dog give en vis dyrkningssikkerhed i forhold til at vælge en enkelt sort, hvor kerneudbyttet kan udvise store variationer fra år til år

Effects of anaerobic digestion of organic manures on N turnover and N utilization

Animal manures and plant-based manures are used for biogas production by anaerobic digestion (AD). After AD the concentration of ammonium-N in manure is increased and the concentration of decomposable C is decreased. Thus, the potential first year fertilizer value of the manure can be increased by the treatment. However, pH is also increased by AD thereby increasing the risk of ammonia losses. The objective of this paper was to compare N turnover in soil after application of digested and corresponding undigested manures, and to compare N fertilizer values of digested manures after direct injection or surface-banding in cereals. After AD of pig and cattle slurry the increase in potential plant availability was equivalent to 10-25% of total manure N. AD of cattle faeces and a mixed cattle diet increased the net mineral N release in soil even more to about 60 and 80% of total N, respectively. The present results indicate that the plant availability of N of digested plant materials is similar to that of digested cattle slurry. After surface-banding of digested manures rich in fibers, such as cattle and plant-based manures, significant ammonia loss can be expected resulting in relatively poor utilization of manure N