Abstract
Nutrient-deficient red soil found in the southern region of China is increasingly being used for potato crops to meet the demand for this staple food. The application of nitrogen fertilizer is necessary to support the production of higher tuber yields; however, the links between nitrate nitrogen and the nitrogen balance in red soil are unknown. A field experiment was conducted in Jiangxi Province in 2017 and 2018 to determine the effects of different nitrogen application rates, 0 kg ha−1 (N0), 60 kg ha−1 (N60), 120 kg ha−1 (N120), 150 kg ha−1 (N150), 180 kg ha−1 (N180), 210 kg ha−1 (N210), and 240 kg ha−1 (N240, the highest rate used by local farmers), on potatoes growing in red soil. Data on tuber yield, crop nitrogen uptake, and the apparent nitrogen balance from the different treatments were collected when potatoes were harvested. Additionally, the content and stock of nitrate nitrogen at different soil depths were also measured. Nitrogen fertilization increased tuber yield but not significantly at application rates higher than 150 kg ha−1. We estimated that the threshold rates of nitrogen fertilizer application were 191 kg ha−1 in 2017 and 227 kg ha−1 in 2018, where the respective tuber yields were 19.7 and 20.4 t ha−1. Nitrogen uptake in potato in all nitrogen fertilization treatments was greater than that in N0 by 61.2–237% and 76.4–284% in 2017 and 2018, respectively. The apparent nitrogen surplus (the amount of nitrogen remaining from any nitrogen input minus nitrogen uptake) increased with increasing nitrogen application rates. The nitrate nitrogen stock at a soil depth of 0–60 cm was higher in the 210 and 240 kg ha−1 nitrogen rate treatments than in the other treatments. Moreover, double linear equations indicated that greater levels of nitrogen surplus increased the nitrate nitrogen content and stock in soils at 0–60 cm depths. Therefore, we estimate that the highest tuber yields of potato can be attained when 191–227 kg ha−1 nitrogen fertilizer is applied to red soil. Thus, the risk of nitrate nitrogen leaching from red soil increases exponentially when the apparent nitrogen balance rises above 94.3–100 kg ha−1.
Highlights
Nutrient-deficient red soil found in the southern region of China is increasingly being used for potato crops to meet the demand for this staple food
Many researchers have reported that more precise control of the total amount of applied nitrogen fertilizer could be an important measure for decreasing soil nitrogen loss[8,9] and the apparent nitrogen balance
Using the system of a potato crop grown in red soil, the objectives of this study were 1) to determine the threshold rate of nitrogen fertilizer application to achieve high tuber yield, 2) to investigate the changes in the nitrate nitrogen content and stock under different nitrogen fertilizer rates, and 3) to determine the relationship between the nitrate nitrogen stock and apparent nitrogen balance
Summary
Nutrient-deficient red soil found in the southern region of China is increasingly being used for potato crops to meet the demand for this staple food. The tuber yield of heritage potato would be decreased under a nitrogen application rate greater than 80 kg ha−1 nitrogen, but the tuber yield of modern potato yield can be increased[18] These potato studies did not investigate crops grown in red soil; determining ideal rates of nitrogen fertilizer application to red soil for achieving high yields of potato while reducing nitrogen pollution is needed. This is because nitrate nitrogen leaches from red soils due to abundant rainfall and high soil erosion, which elevates the importance of developing more sustainable fertilization strategies in fields with red soil
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