Sanna Kukkonen

The impact of crop plant cultivation and peat amendment on soil microbial activity and structure

AbstractA rapid means for restoring soil fertility could be addition of peat to the plough layer. The impact of cultivation of eight different crops (the joint impact of plant and the management tailored for each plant), with and without soil amendment by peat treatment on soil microbiological, physical and chemical properties was assessed for two consecutive growing seasons. As a measure of the functional diversity of soil microbial community we estimated the activity of several different extracellular soil enzymes using the ZymProfiler® test kit. ATP content was measured to yield information on the amount of the active microbial biomass, and phospholipid fatty acid (PLFA) profiles were analysed to reveal the microbial community structure. The enzyme activity patterns of the soil samples indicated several differences due to the different crops and years but ATP content and PLFA profiles were rather stable. However, microbial biomass as total amount of PLFAs depended on the plant and peat treatment and ATP content varied between the years. The effects of the peat treatments were less clearly indicated by the biological parameters one or two years after the amendment, as only arylsulphatase and β-xylosidase activities were affected in both the years. Soil moisture, affecting enzyme activities, depended on the year and crop plant and peat addition increased it. Abbreviations: AMC – 7-amino-4-methylcoumarin; AP – aminopeptidase; ATP – adenosine triphosphate; Cmic– microbial biomass carbon; DNA – deoxyribonucleic acid; EC – electrical conductivity; FAME – fatty acid methyl ester; fw – fresh weight; MUF – 4-methylumbelliferyl; na – not added; Nmic– microbial biomass nitrogen; PDE – phosphodiesterase; PLFA – phospholipid fatty acid; PME – phosphomonoesterase; SOM – soil organic matter

Fruit development in artificially self- and cross-pollinated strawberries (Fragaria × ananassa) and raspberries (Rubus idaeus)

Tunnel cultivation of berries is increasing on a global basis, and suitable management techniques are being studied for growing berry crops in a protected environment. Soil mulching and irrigation are among the techniques that significantly affect plant growth and yield. Tunnel cultivation is often limited to growing single cultivars, and little attention has been paid to the effects of growing several cultivars in the same tunnel. There are indications that crop yield and quality might benefit from cross-pollination. In this study, the effects of artificial self- and cross-pollination were studied in 15 strawberry and 6 red raspberry cultivars grown in a protected environment in a greenhouse. Four strawberry cultivars benefited from cross-pollination and one required it. In the case of raspberries, self- and cross-pollination had no effect on yield and fruit quality. In conclusion, particular berry cultivars are better suited to tunnel cultivation.

Biological control of strawberry crown rot is substrate dependent phenomenon

BACKGROUND: Phytophthora cactorum crown rot is currently limiting strawberry cultivation worldwide. Arbuscular mycorrhizal fungi (AMF) and bacterial endophytes have shown promising results as biological control against the disease. Growing medium can also influence biological control and e.g., composts have been shown to suppress soil borne pathogens. OBJECTIVE: The aim of the study was to investigate the effect of AMF, endophytic bacteria and different growing media against strawberry crown rot. METHODS: Three pot experiments were conducted in greenhouse conditions. Each experiment tested different biological control methods with micropropagated strawberry ‘Jonsok’ inoculated or not with the fungus. The first experiment evaluated AMF strains on different growing media, the second experiment tested combinations of AMF and other biocontrol microbes. The third experiment tested the impacts of AMF, Pseudomonas fluorescens and compost. RESULTS:Biological control methods and disease inoculation had very different impacts on strawberries planted in different growing media. On suitable growing media, AMF increased growth and lowered disease symptoms, but P. fluorescens was not effective. The growing medium containing manure/wood fiber compost was the most disease suppressive. CONCLUSIONS: Biological control of strawberry crown rot with AMF is substrate dependent. Composts can be used to somewhat suppress crown rot.