Effects of traffic and fertilization levels on grass yields in northern Norway

Experiments with various traffic regimes in grassland (no traffic, light and medium tractor with two mechanisation lines; forage harvester and two-step harvesting) and three fertilization levels (N 120, 180, 240 kg ha-1) were carried out in five fields on sandy soils and peat soils in Bodø, northern Norway. Increased tractor weight caused significant decrease in yields on the peat soils with both mechanisation lines. When the peat soils were exposed to the light tractor treatments, DM yields increased significantly as the fertilization level rose from N 120 kg ha-1 to N 180 kg ha-1, but not for further increase to N 240 kg ha-1. With the medium tractor treatments, there was no significant yield increase from N 120 kg ha-1 to N 180 kg ha-1, but a further increase to N 240 kg ha-1 gave significantly higher yields. Use of lighter machines on peat soils may therefore lead to reduced fertilizer costs for farmers, and decrease the risk of leaching from the soil. On the sandy soils, yields were significantly lower at the medium tractor treatment with two-step harvest compared to no traffic. With the exception of decreased air-filled porosity at 1-5 cm depth of the peat soils no significant change in soil physical properties of the plough layer were measured. Therefore, the negative impact of traffic on plant growth was more likely due to plant injury than impaired soil conditions.vo

Bynær dyrking med resirkulert gjødsel? En vurdering av tungmetallrisiko

Mange som dyrker grønnsaker til direkte salg er interessert i økologiske driftsmetoder. Det er mye organisk materiale tilgjengelig i byer og tettbygde strøk. Matrester og avfall fra hager og parker kan bli til både energi og gjødsel, som kan brukes i dyrking av grønnsaker i bynære strøk. Da får vi korte verdikjeder, men hva med innholdet av tungmetaller? Beregninger viser at grenseverdier i jord vil mettes først for kobber og sink, som også er viktige mikronæringsstoffer. for planter. Jordforbedringsmidler med høyt innhold av organisk materiale, som hage-park kompost og hestegjødsel, inneholder mer tungmetaller per kg tørrstoff enn fjørfegjødsel og utråtnet matavfall

Effects of traffic and fertilization levels on grass yields in northern Norway

Experiments with various traffic regimes in grassland (no traffic, light and medium tractor with two mechanisation lines; forage harvester and two-step harvesting) and three fertilization levels (N 120, 180, 240 kg ha-1) were carried out in five fields on sandy soils and peat soils in Bodø, northern Norway. Increased tractor weight caused significant decrease in yields on the peat soils with both mechanisation lines. When the peat soils were exposed to the light tractor treatments, DM yields increased significantly as the fertilization level rose from N 120 kg ha-1 to N 180 kg ha-1, but not for further increase to N 240 kg ha-1. With the medium tractor treatments, there was no significant yield increase from N 120 kg ha-1 to N 180 kg ha-1, but a further increase to N 240 kg ha-1 gave significantly higher yields. Use of lighter machines on peat soils may therefore lead to reduced fertilizer costs for farmers, and decrease the risk of leaching from the soil. On the sandy soils, yields were significantly lower at the medium tractor treatment with two-step harvest compared to no traffic. With the exception of decreased air-filled porosity at 1-5 cm depth of the peat soils no significant change in soil physical properties of the plough layer were measured. Therefore, the negative impact of traffic on plant growth was more likely due to plant injury than impaired soil conditions.vo

Soil fertility in three cropping systems after conversion from conventional to organic farming

Temporal changes in the scores of selected soil fertility indices were studied over six years in three different cases of organic crop rotation located in southern, eastern and central Norway. The cropping history and the initial scores of fertility indices prior to conversion to organic cropping differed between the sites. Crop yields, regarded as an overall, integrating fertility indicator, were in all rotations highly variable with few consistent temporal trends following the first year after conversion. On the site in eastern Norway, where conversion followed several years of all-arable crop rotations, earthworm number and biomass and soil physical properties improved, whereas the system was apparently degrading with regard to P and K trade balances and contents in soil. On the other two sites, the picture was less clear. On the southern site, which had a relatively fertile soil before conversion, the contents of soil organic matter and K decreased during the six-year period, but the scores of other fertility indices showed no trends. On the site in central Norway, there were positive trends for earthworm-related indices such as worm biomass and tubular biopores, and negative trends for soil porosity. The results, especially those from the eastern site, illustrate the general difficulty in drawing conclusions about overall fertility or sustainability when partial indicators show divergent trends. Consequently, the study gave no unambiguous support to the initial working hypothesis that organic farming increases inherent overall soil fertility, but rather showed that the effect varied among indicators and depended on status of the cases at conversion. It is concluded that indicators are probably better used as tools to learn about and improve system components than as absolute measures of sustainability

Agricultural experimental sites

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