Organic sugar beet production. Weed control and organic fertilisation.

摘要

Since April 2003, the use of conventional sugar in organic processing products is not permitted any more. This has resulted in a considerable increase in demand for organic sugar, often met by imports with cane sugar carrying high food miles. Local organic sugar beet could be an alternative, however sugar beet is a very uncommon crop in organic systems mainly because of problems with weed control, fertilisation and other crop management issues. In 2003, replicated field trials were conducted on five German sites in Lower Saxony, Saxony and Franken (Bavaria). Results showed that a drilling date a fortnight later (22 April instead of 7 April) and previous shallow cultivation to stimulate germination of weeds reduced weed pressure considerably. Between 20-40 weeds per ha were counted compared to 120/ha with early drilling. Ploughing in autumn compared to spring had also a positive effect on weed pressure reducing weeds per ha to below 10/ha. Other non-chemical weed control like harrowing or flame weeding had only minor effects. Hand labour for weeding was 100h/ha for spring ploughing and 80h/ha for autumn ploughing. The late drilling produced however lower yields (15% lower or 50.3 t/ha) and in combination with spring ploughing this amounted to 22% yield reduction (46 t compared to 59.3 t/ha). This is considered to be caused by slower plant development and shortage of water following the ploughing in spring. Organic fertilisation with 50 kg N/ha in October as either farm yard manure, oil seed rape meal or green manure as Persian clover (Trifolium resupinatum) showed no effect on yields. There was a tendency of higher amino-N contents and lower adjusted sugar beet yields, however these are annual results effected by the water shortage in 2003..