Koskela E.,Applied Plant Research PPO |
Koskela E.,University of Helsinki |
Kemp H.,Applied Plant Research PPO |
Van Dieren M.C.A.,Applied Plant Research PPO
Acta Horticulturae | Year: 2010
One of the most important factors affecting the financial outcome of commercial fruit growing is the success of pollination and fertilization, which in turn are dependent on weather conditions, activity of pollinators and the compatibility and overlap in flowering of the cultivars. Before introducing new cultivars, it is obviously important to know the compatibility and flowering characteristics of the genotypes. In order to find out these attributes of seven new and four established plum cultivars, pollen germination tests, hand pollinations and flowering phenology observations were carried out. 'Prosser 84' had 70% pollen germination. 'Opal' had just 3%, probably due to aged pollen. 'Anna Späth' flowered over a short period (13 days) and '1468' and 'DCA BO 46' over long (19 days) periods; the overlap of all cultivars was relatively good. With '1468', 'Victory', 'Anna Späth' and 'Prosser 84' flowering intensity varied between years, 'Jubileum', 'V70032', 'Tita' and 'DCA BO 46' flowered regularly, the others were intermediate. '1468' and 'WJ 65' flowered early, 'Prosser 84' and 'DCA BO 46' late and the rest fell in between. 'Victoria' proved to be self-fertile, 'Jubileum', 'V70032' and '1468' semi self-fertile. Fruit set percentages after June drop of all crosses were rather low; varying between 0 and 28%. With 'Tita', fruit drop occurred approximately two weeks later than with the other cultivars.
Crittenden S.J.,Wageningen University |
Poot N.,Wageningen University |
Heinen M.,Wageningen University |
van Balen D.J.M.,Applied Plant Research PPO |
Pulleman M.M.,Wageningen University
Soil and Tillage Research | Year: 2015
Reduced tillage can improve soil physical quality relative to mouldboard ploughing by lessening soil disturbance, leaving organic matter at the soil surface, and stimulating soil biological activity. In organic farming, continuous ploughing may negate benefits to soil structure and function from increased use of manures and more diverse crop rotations, which are particularly important components of organic farming. The current study examined soil physical quality (i.e., properties and functioning) of a 4-year old reduced tillage system under organic and conventional farming with crop rotations that included root crops. Reduced tillage was compared to conventional mouldboard ploughing (MP) in 2 organic fields at different points of the same crop rotation (Org A and Org B) and 1 conventional field (Conv A). Reduced tillage consisted of non-inversion tillage (NIT) to 18-23. cm depth whereas MP was characterised by annual mouldboard ploughing to 23-25. cm depth. NIT improved soil water retention in Org B but had no effect in Org A. NIT increased soil aggregate stability at 10-20. cm depth compared to MP in all fields, and additionally at 0-10. cm in Conv A. Penetration resistance was higher in NIT in all fields. Furthermore, soil organic matter content was higher in NIT than MP at 0-10. cm depth in all fields and at 10-20. cm in Org B and Conv A. NIT increased carbon stocks in Org B but not in Org A. NIT statistically increased crop yields in spring wheat/faba bean mixture in Org A, and there was no yield penalty from NIT in Org B spring wheat nor Conv A sugar beet. In contrast, field-saturated hydraulic conductivity in all fields in autumn was lower in NIT. Differences in crop (i.e., phase of rotation) and associated organic inputs between Org A and B likely accounted for the differences in effects of tillage system. Overall, the NIT system improved or imposed no penalty on soil physical quality (except field-saturated hydraulic conductivity) and improved or imposed no penalty on crop yields and could therefore be considered as a viable alternative for farmers. © 2015 Elsevier B.V..
Kohl J.,Wageningen University |
Vlaswinkel M.,Applied Plant Research PPO |
Groenenboom-de Haas B.H.,Wageningen University |
Kastelein P.,Wageningen University |
And 3 more authors.
Plant Pathology | Year: 2011
Mycosphaerella brassicicola (ringspot), Alternaria brassicicola and A. brassicae (dark leaf spot) and Xanthomonas campestris pv. campestris (black spot) can infect leaves of Brussels sprouts resulting in yield losses. Infections of outer leaves of sprouts cause severe losses in quality. Crop residues can be a major primary inoculum source of the pathogens. Their population dynamics were followed in residues of leaves and stalks of crops of Brussels sprouts during 24months using real-time PCR assays. Leaf residues on the soil surface or buried in soil decomposed within 4months. However, residues of stalks were present in the field after 24months. In such residues, M. brassicicola populations increased during the first 2months, but decreased thereafter and the pathogen was found only occasionally in the second year. Alternaria brassicicola multiplied on stalks exposed on the surface of field soil and was present on such residues after 24months. Survival was less on residues buried in soil. Alternaria brassicae population increased in stalks exposed on the soil surface during the first months but decreased thereafter under the detection limit. Xanthomonas campestris cv. campestris populations fluctuated in time but 1×10 4cellsmg -1 stalk residue were still found after 24months. Additionally, the four pathogens were present in residues of 11 commercial rapeseed crops that were analysed. The observed variation in population sizes of the pathogens between individual pieces of crop residues indicates a stochastic spread of pathogens. Unravelling the underlying processes will support the development of novel methods for sustainable disease prevention. © 2011 The Authors. Plant Pathology © 2011 BSPP.
Leeuwen P.J.V.,Applied Plant Research PPO |
Trompert J.,Applied Plant Research PPO
Acta Horticulturae | Year: 2011
Several bulbous crops like Crocus, Allium and some species of Tulipa and Narcissus can be infected with the nematode Aphelenchoides subtenuis. The nematodes cause retarded growth, poor or no flowering and eventually death of the bulbs and corms. A hot water treatment after lifting the bulbs has proved to be effective in controlling the nematodes. Due to a high incidence of infected stocks of bulbs a study was conducted to establish if the efficacy of the treatment could be improved by altering the timing and the temperature of the hot water treatment and the storage temperature of the bulbs prior to the hot water treatment. Bulbs and corms of Allium and Crocus were given a hot water treatment of four hours at 43.5 or 45°C. Between lifting and the hot water treatment the bulbs were stored at 25 or 30°C. Prior to the hot water treatment some of the bulbs were immersed in water for 24 hours. The hot water treatment was performed at 7, 10, 12 or 14 days after lifting the bulbs or corms. Controlling Aphelenchoides subtenuis was only effective when the hot water treatment of four hours at 45°C was applied within 10 to 14 days after lifting the bulbs. When Crocus was stored at 30°C a hot water treatment was only effective until 10 days after lifting. When stored at 25°C a treatment was effective until 14 days after lifting. The hot water treatment became more effective when the bulbs were immersed in water for 24 hours prior to the hot water treatment.