The effect of timing of ridging on soil inorganic nitrogen and potato tuber yield and quality

Summary

Field experiments were conducted on sand and sandy loam from 2000-2002 to determine how timing of ridging affects potato tuber yield and quality depending on soil type and the use of catch crops. On sand, ridging in winter increased nitrogen availability in the 0-50 cm soil layer in spring by 19% from 5.7 to 6.8 mg N/kg soil compared with ridging in autumn (P<0.001) and by 8% from 6.3 to 6.8 mg N/kg soil compared with ploughing in spring (P<0.05). With a total and marketable yield of 27,9 t/ha and 14,2 t/ha respectively, ridging in winter resulted in higher tuber yield than both ridging in autumn and ridging in autumn combined with tilting and re-establishment of ridges in winter. These yield results were comparable to spring ploughing, but because of the ability to perform direct potato planting in the winter ridges on sand workload was significantly reduced. Ridging in autumn slightly improved tuber quality but reduced yields.
On sandy loam there was no effect of timing of ridging. Ridging in winter resulted in similar levels of soil inorganic nitrogen and similar tuber yields as ploughing in autumn, but because ridges had to be rotovated in spring before planting to create a sufficiently loose soil, workload was not reduced. It is concluded that ridging in winter in combination with a ryegrass catch crop represents a potent alternative for organic potato production on sand but not on sandy loam.