Search

The cereal often dominates the grain legume in intercrops, especially when sown in larger amounts. This study assessed yield formation of pea (Pisum sativum L.) and oat (Avena sativa L.) in an intercropping system in high-latitude conditions. Three pea cultivars (Hulda, Karita and Perttu) and one oat cultivar (Roope) were grown as sole crops and intercrops with shares of either 7.5% or 15% of oat (as weight of sown seed mixture). Experiments were organized in three (southern, western and northern) locations of Finland for three years. Yield and vegetative above-ground biomass, their land equivalent ratio (LER, i.e., the yield in intercrop compared to that of the component yields in pure stands), and a number of yield components were measured prior to harvest at crop-stand and single-plant levels. The share of oat in the intercrop did not have any impact on variation in LERyield. Oat yield and yield components generally benefitted from a pea companion crop. The pea cultivar Perttu was superior in intercrops: it had a LERyield>1 in seven out of eight experiments (mean LERyield=1.06), while Karita had a LERyield>1 in four (mean LERyield=1.00) and Hulda only in one experiment (mean LERyield=0.98). Perttu proved to be a compatible pea companion for a pea-oat intercrop, likely because it was successful in overcompensating for decline in relative yield (RGY) of oat in intercrops, contrary to Hulda. However, none of the measured yield components of Perttu were associated with LERyield, suggesting compensation ability between them, while in Karita and Hulda, e.g., higher grain yield and number of grains and pods per square meter were associated with decline in LERyield. It was concluded that the success of Perttu as a companion for oat in intercrops is likely attributable to its flexibility in building yield through a variable combination of yield components rather than being outperformed due to some superior traits. Such flexibility, likely attributable to long duration of flowering supports resilience to weather variability that is typical for northern European conditions allowing Perttu to consistently sustain a LERyield >1.

The release of CO2 from the snow surface in winter and the soil surface in summer was directly or indirectly measured in three different soil types (peat, sand and clay) in agricultural ecosystems in Finland. The closed chamber (CC) method was used for the direct and Pick’s diffusion model (DM) method for the indirect measurements. The winter soil temperatures at 2-cm depth were between 0 and 1°C for each soil type. The concentration of CO2 within the snowpack increased linearly with snow depth. The average fluxes of CO2 calculated from the gradients of CO2 concentration in the snow using the DM method ranged from 10 to 27 mg CO2 m2h-1 and with the CC method from 18 to 27 mg CO2 m2h-1. These results suggest that the snow insulates the soil thermally, allowing CO2 production to continue at soil temperatures slightly above freezing in the winter. Carbon dioxide formed in the soil can move across the snowpack up to the atmosphere. The winter/summer ratio of CO2 evolution was estimated to exceed 4%. Therefore, the snow-covered crop soil served as a source of CO2 in winter, and CO2 evolution constitutes an important part of the annual CO2 budget in snowy regions.

The study was conducted to investigate the effect and benefit of applying plant growth regulators (PGR) to two easily lodging barley cultivars, Arra and Kilta, which were commonly used for fodder production all over Finland. Field trials were conducted at six experimental sites in different parts of the country. Of the PGRs tested, ethephon and mepiquat/ethephon were the most effective in shortening the culm and preventing lodging. However, neither could prevent the lodge adequately in all growing circumstances. When applied at flag-leaf stage (FS 10) they increased yield under conditions favourable for lodging. They also raised the volume weight of barley, which was important for the final price of the yield. The most important factors determining future lodging of barley were an effective temperature sum of over +5°C and precipitation during the period from sowing to the beginning of tillering (FS 2). About 64-68% of the lodging risk of the cultivars studied could be predicted from weather conditions during early development of the crop. Local growing conditions and the presence of lodge had a marked impact on the results obtained with PGRs. In the case of moderate lodging the compound used determined whether a profit or loss was made on the crop. In the case of heavy lodging, compounds containing ethephon contributed to an economic return. Their application at flag-leaf stage gave a profit of FIM 70 - 390 ha-1. Since the profitability of PGR treatments depended on lodging, treatments are recommended for fodder barley only when lodging is expected. The lodging risk can be predicted within certain limits at the tillering stage of barley.