Smart seed : fördröjd groning hos raps : försök med frö-coating samt litteraturgenomgång om frögroning, coating och praktisk tillämpning i reläodling

Abstract: Oilseed rape constitutes a good break crop within a cereal dominated cropping system. The normal sowing time for winter rape in Sweden is August. It's a time in the cropping year characterized by a heavy work load, such as harvest and soil management. In addition, it is often a period with large precipitation. Thus, it is sometimes problematic for the farmer to do the sowing of winter rape at the optimal time. A relay cropping system with spring cereal and winter rape might be of great benefit for the farmer and the environment. This thesis is based on the idea of sowing a spring cereal crop and winter rape at the same time in the spring. The spring cereal will grow as usually, while the rape seeds are coated with a material, which delays germination. After three months, the rape seed will germinate and thus, be in the seedling stage when it's time to harvest the spring cereal. With this system the rape seed will always be seeded in right time and little additional work is needed in an already stressful period of the cropping year. In this thesis different types of wax were tested as a way to prevent germination of rape seeds. The waxes included an acid, base or a neutral phase. The function of the wax was to prevent water, which is a primary factor for germination, to reach the seed. The base or acid phase was hypothesised to break down the wax slowly and subsequently enable the seed to take up water and germinate. The results from the experiments showed that it is difficult to find a chemical, which can meet the requirements of delayed germination with a built-in time factor. The acid fraction was shown to harm the seed while breaking down the wax. The base fraction, on the other hand, did no damage the seed at a low concentration but the wax was not sufficiently degraded. The seeds were shown to survive in the waxy layer for one month. However, after three months covered by wax the seeds were dead. The wax layer had too little permeability and the seeds were probably killed by carbon dioxide poisoning and/or lack of oxygen. Earth living organisms can also be a problem as they were the probable cause for the breakdown of the wax in the experiments presented here.