Effects Of Grass-Clover Silage Quality And Application Rate On Organic Potato Performance

Most organic farmers use animal manure as a source of crop nutrients. However, recent experiments have revealed that cut-and-carry fertilisers like grass-clover silage may provide a viable alternative. The objective of the current study was to investigate the performance of an organic potato crop on a sandy soil fertilised with grass-clover silages differing in C: N ratio (16, 17, 22 and 24) and nitrogen application rate (0, 57, 113 and 170 kg N ha-1). The total tuber yield was highest for the silage with a C: N ratio of 16 (44 Mg ha-1). However, the yield difference with the silage having a C: N ratio of 24 was not more than 10% (40 Mg ha-1). In terms of N application rate, there was a linear increase in yield with N rate while the share of marketable potatoes also improved with N-rate. In the non-amended control, the potato yield was 30.5 Mg/ha, whereas with 170 kg N ha-1 this was 47.5 Mg/ha. The agronomic nitrogen efficiency (ANE; kg tubers per kg applied N) was not affected by either the C: N ratio or the N application rate. However, ANE values tended to be highest for the C: N ratio of 16 (115 kg tubers/kg N) and an application rate of 170 kg N ha-1 (100 kg tubers/kg N). Overall, crop performance and N-utilisation were more than adequate which underlines that grass-clover silage can be considered as a potential substitute for animal manure sources