Bengt Lundegårdh

Organically produced plant foods: Evidence of health benefits

If in plant secondary metabolites, the presence of pesticides and nutritional balances are the most important determinants of nutritional value of food plants, then organically produced plant foods could be expected to bemore health-promoting than conventional foods. Differences arise in management practices between organic and conventional farming where the former support (a) an activation of the plant defence mechanisms by excluding synthetic plant protection agents, (b) an active soil life where plants and microbes interact, exchanging certain metabolic compounds and (c) a balanced mineral nutrient uptake where excesses of easily available nutrients are avoided.

Interaction between a fungal plant disease, fungivorous nematodes and compost suppressiveness

Abstract We tested the hypothesis that the fungivorous nematodes Aphelenchoides spp. and Aphelenchus avenae can suppress damping-off caused by Rhizoctonia solani in cauliflower seedlings, and enhance the disease-suppressive effect of compost. In greenhouse experiments, we used two different composts mixed with peat (20% + 80%) and pure peat as growth substrates in growing pots. In each substrate, treatments were: (A) with R. solani and nematodes, (B) with R. solani, (C) with nematodes, (D) control without R. solani or nematodes. Treatment effects were measured as percentage of healthy seedlings 7, 10 and 14 days after start of the experiment. We conducted two different experiments with the treatments A–D; one with Aphelenchoides spp. and one with Aphelenchus avenae. Aphelenchoides spp.+R. solani (treatment A) had 85% healthy plants (= control without addition of fungi (D)) compared with 45% in R. solani without nematodes (B). Aphelenchus avenae suppressed damping-off significantly in all substrates, from almost 100% dead plants in peat with R. solani to 65% healthy plants in R. solani+A. avenae. One compost mixture had an intrinsic suppressive effect on damping-off, while plant health in the other compost mixture was not better than in 100% peat as growing substrate. There were no additive suppressive effects (enhancement) between nematode effects and the suppressive compost. The results demonstrate the ability of fungivorous nematodes to suppress plant diseases. The effects of fungivorous nematodes in combination with compost and other control measures on disease suppression need further attention. The usefulness of fungivorous nematodes in agriculture and horticulture is discussed.

A Test System with Limited Beds for Evaluation of Growing Methods, Applied to Ecologically Cultivated Greenhouse Tomatoes (Lycopersicon esculentum Mill.)

ABSTRACT A test system for fertilization studies of greenhouse crops was designed during the period 1990–1992. The growth substrate was kept in separated beds, constructed as large shallow boxes, in which cultivation could be performed with good control of nutrient inputs and losses. The system had qualities for controlled growing similar to pot experiments, without having their disadvantage of holding small volumes of test substrate. All types of fertilizers might be supplied to the growing system. As the drainage water could be collected from each bed in the test system, it was also possible to determine the risks for nutrient losses with subsequent polluting effects. The test system was applied on ecologically cultivated greenhouse tomatoes, obtaining their nutrients from a substrate of farmyard manure compost and mulch of freshly cut plant material. The yield obtained was similar to that from conventionally cultivated greenhouse tomatoes. The described growing system, allowing good control of the nutr...

Ecological Cultivation of Greenhouse Tomatoes (Lycopersicon esculentum Mill.) in Limited Beds Fertilized with Locally Produced Mulches: Effects on Growth and Yield

ABSTRACT Fertilization of ecological cultivating systems for producing greenhouse tomatoes with locally produced mulches was studied from 1993 to 1995. The tomato plants were cultivated in limited growth beds filled with nutrient-poor substrate, consisting of farmyard manure (FYM) compost, straw and soil subsequently mixed with peat and gypsum. Mulches of freshly cut grass or clover or a mixture of the two were placed on the surface of the substrate to assess their value as fertilizer. Fruit yield, fruit quality, plant length and NPK-content of mulch materials and bed water were regularly measured. Comparisons made on four occasions during each growing season showed that the mulches containing clover produced significantly higher yield than the grass mulch and this treatment also had the best utilization of P and K. Nitrogen utilization was highest in beds fertilized with grass mulch, even though the yield was lower. Combined mulch of grass and clover produced intermediate yield and had good utilization o...

The N and S status in cropping systems with white cabbage as influenced by organic fertilizers

Abstract Fresh and anaerobically digested red clover were compared as N and S sources in a incubation experiment without plants and a pot experiment with white cabbage, both conducted in climate chambers. The hypothesis was that anaerobic digestion would increase S availability in relation to N and that arylsulphatase activity would be higher in treatments with S deficiency. Besides the two red clover-based treatments, two treatments, one unamended and the other Biofer, an organic fertilizer with 7% S containing by-products from the slaughter industry, were included in the experiments. The availability of S in relation to N was higher in biogas slurry than in fresh red clover. In the incubation, an equal percentage (approx. 50%) of N was mineralized from all three fertilizers, while in the pot experiment, N mineralization was highest in the red clover treatment (approximately 70%). The highest S mineralization in both experiments occurred in the Biofer treatment. Growth of white cabbage was higher in the biogas slurry than in the red clover treatment despite high N availability in the latter treatment. Immobilization of S due to more readily available C in the clover treatment could have reinforced the difference and given a less well adjusted relationship between N and S for white cabbage demand than in the biogas slurry treatment. Arylsulphatase activity in the bulk soil was higher in the red clover-based treatments than with Biofer, while the activity in the rhizosphere soil did not differ between treatments. Arylsulphatase activity in the bulk soil was negatively correlated with white cabbage S concentration and positively correlated with N:S ratio in white cabbage shoots, while that in the rhizosphere soil was positively correlated with white cabbage S concentration.