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Leader project: “Hallertau model for resource-saving hop farming”
Initial situation and objective Hop farming is the main form of crop husbandry in the Hallertau region. The focus on hop farming in this region has evolved over time and has shaped the cultural landscape. Hop cultivation is resource-intensive and therefore harbours ecological risks, one of which is the high degree of soil erosion susceptibility associated especially with row crops such as hops. Another is the large amount of nitrogen needed in hop-growing in order to obtain optimum yields and qualities. The problem here is that hop plants take up most of their nitrogen relatively late in the vegetation season, from mid-June to August. Nitrogen remaining in the soil can no longer be used in autumn and winter and is subject to displacement or even leaching. Minimizing nitrogen leaching, however, is a crucial waterconservation issue. Scientific studies have also shown that nitrogen absorption in hop is poor, necessitating a rich supply of nitrogen if optimal yields are to be obtained. The nitrogen is often taken up incompletely, remaining in the soil after harvesting in the form of nitrate. Within the leader model project of the Hallertau water board, in which various partners from agencies and associations work together, the aim is to investigate whether modified nitrogen strategies will enable commercial hop farming to remain feasible without neglecting groundwater protection requirements. Method Initial trials in the Hallertau region and in Thuringia showed that if fertiliser is applied by banding (2-m band) rather than broadcasting, the same yield can be achieved with approx. a third less fertiliser. One aim of the research project “Hallertau model for resource-saving hop farming”, scheduled to run from 2009-2015, is to verify this finding. To achieve this aim, N-fertilisation trials will be performed in several replications, in which N application by broadcasting (240 kg N minus Nmin) is compared with banded application (2-m band) using a third less fertiliser. In order to obtain insight into nitrogen dynamics in the soil around the hop plants, we intended to simultaneously measure substance transfer at various depths (0.5 m, 1.2 m, 2.0 m and 4.0 m) in the soil of the different variants using suction cups. Limited project funding meant we could only install a suction-cup system in one replication, making a statistically significant yield evaluation of a trial harvest impossible. Twenty hop plants were nevertheless harvested at our own expense from each of the plots fertilised by broadcasting or banding. The yields were determined and the alpha-acid contents measured. Results The trial crop was not harvested in 2010 because severe infection with primary downymildew had caused highly disparate plant growth. It was also feared that, on account of the extensive digging activity connected with installation of the suction-cup system in spring 2010, the soil profile would still be disturbed to such an extent as to preclude uniform soil and growing conditions.
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