Abstract
Potato is the fourth most important staple crop in China. To meet the increased demand and environmental objectives, potato production should be enhanced by sustainable practices that aim to maximize yield and resource use efficiencies and minimize environmental impacts. Most experiments so far have taken place on experimental stations, while on-farm experimentation is needed to evaluate, demonstrate and scale more sustainable practices. On-farm field experiments were conducted in two years (2017, 2018) in northern China to investigate and demonstrate the effects of different nitrogen (N) fertiliser and irrigation input levels on potato yield, quality, resource use efficiency and environmental impacts. The 2017 experimental results on one farmer’s field showed that under irrigated conditions, adding N fertiliser (from 0 to 267 kg ha−1) did not increase yield due to the high soil N supply, rather it reduced tuber quality. The 2018 experimental results, in which four additional farmers were involved, indicated that, under irrigated conditions, reducing N fertiliser from the current rates (189–252 kg ha−1) to lower levels (109–181 kg ha−1) did not affect yield nor quality; while further reducing N fertiliser inputs (to 9–117 kg ha−1) resulted in a yield reduction (18% on average) in some fields. In both years, irrigation improved tuber yield and quality compared to that under rainfed conditions. The nitrogen use efficiency was improved and N surplus was reduced by applying irrigation and reducing N fertiliser input. Farmers expressed they were willing to reduce N fertiliser input by 10–20%, and indicated that a widespread adaptation of drip irrigation is hindered by the high costs and labor requirements. Site-specific recommendations on optimum N fertiliser and irrigation management must be provided, which should preferably be based on regular quantitative monitoring of soil N supply and soil moisture content.
Highlights
In the 2017 experiment, yield showed no significant response to N fertiliser input under irrigated conditions (Figure 1a), which indicates that the soil
2017, under the full irrigation treatment the soil water moisture level was not maintained at 80% of field capacity (FC) which led to water-limited growth and a reduction in yield (Figure S3)
The results are in agreement with the finding that enhancing yield was associated with an improvement of various quality aspects [20]
Summary
Potato in northern China is mainly cultivated as a cash crop and large-scale commercial production often receives large amounts of nitrogen (N) fertiliser input [5]. Excessive N fertiliser application has long been a common practice in China, which has caused low nitrogen use efficiency (NUE) and severe environmental problems [6,7]. For large-scale commercial potato production in northern China, the current NUE, defined as the N output in tuber yield as a percentage of the N input in fertilizers and atmospheric deposition, is moderately high (47–68%) and N surplus (50–156 kg N/ha) is high due to the high N fertilizer input (up to 500 kg ha−1 ) and soil N supply [8]. Excessive application of N fertiliser has little beneficial effect on yield due to the “diminishing marginal return principle” [9], and has a negative effect on tuber quality (e.g., low tuber dry matter concentration) [10]
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