2020 Volume 91 Issue 5 Pages 341-350
To develop nitrogen fertilization based on soil autoclaved nitrogen (AC-N) for potato of processing, which enables to decide optimum nitrogen fertilizer amount augmenting vendible tuber yield, lots of field experiments in not only agricultural experiment stations but farmers’ fields were conducted, with using leading cultivars (“Toyoshiro” and “Snowden”).
Although 30–60 kg ha−1 increase of nitrogen fertilizer gave lower potato starch content statistically-significantly, the lowering was little as only 0–4 g kg−1. Therefore, the effect of the 30–60 kg ha−1 increase of nitrogen fertilizer on potato starch content seemed small.
Nitrogen uptake by tuber at the harvest was closely proportional to the vendible tuber yield, which leveled off at 100–110 kg ha−1 of nitrogen uptake.
On the other hand, we found that AC-N was significantly proportional to nitrogen uptake by tuber at the harvest in the no-nitrogen fertilizer plots, which leveled off at approximate 100 mg kg−1 of AC-N. Additionally, the nitrogen uptake when the previous crop was sugar beet was 20–70 kg ha−1 larger than the other cases.
Based on the above results, nitrogen fertilization method for potato was experimentally made. Optimum nitrogen uptake at the harvest was hypothetically set as 110 kg ha−1, and nitrogen uptake from soil was estimated by the proportional relationship between AC-N and nitrogen uptake in the no-nitrogen fertilizer plots. Effect of difference among the previous crops (sugar beet or others, etc) on nitrogen uptake was also taken into consideration.
Analyzing fitness of the experimentally-made nitrogen fertilization method showed that the fitness was not sufficient in some cases, where AC-N was over 110 mg kg−1, or the previous crop was sugar beet, or soil nitrogen provision was excess over due to some unknown reasons. However, in 75% of the total cases, the fitness was sufficient; therefore, the developed nitrogen fertilization was sufficiently useful.
