{'fraction_non_alphanumeric': 0.05, 'fraction_numerical': 0.07413793103448275, 'mean_word_length': 4.634304207119741, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The potential for N2O emission and nitrate leaching in seasonally open solar greenhouses during the summer fallow: a 15N tracer study

The mechanisms responsible for nitrous oxide (N2O) emission and the potential for nitrate leaching under seasonally open solar greenhouses were investigated in a nitrogen‐15 (15N) tracer study during the summer fallow period in Yangling, Shaanxi Province, China. 15N‐labelled urea and KNO3 were applied at 30 (U1, K1) and 60 (U2, K2) kg N/ha, respectively, to microplots in a solar greenhouse after harvest of tomatoes. Large N2O emissions resulted from each treatment, with a total N2O flux of 482, 1481, 2283, 656 and 991 g N/ha for control (CK), U1, U2, K1 and K2, respectively, were primarily observed during the first month of the summer fallow period, reflecting the combination of considerable residual nitrate, soil organic matter and rainfall. The total 15N‐N2O flux was 35.2, 37.2, 7.9 and 11.2 g N/ha for U1, U2, K1 and K2, respectively, accounting for 0.54, 0.40, 0.17 and 0.12% of the applied N, suggesting that both nitrification and denitrification contributed to the enhanced N2O emission. After 2 months of fallow, only 52.08–54.78% of applied 15N remained in the top 0–40 cm soil layer, where there was the main concentration of tomato roots. Of the total 15N‐labelled KNO3 applied, 86.76% (K1) and 82.06% (K2) remained in the 0–100 cm soil layers and the rest of the N (about 13.07% for K1 and 17.82% for K2, calculated by subtracting 15N‐N2O loss and 15N remaining in the 0–100 cm soil layers from the total applied 15N) leached below 100 cm. Solar greenhouses in north‐west China clearly have great potential for both N2O emission and nitrate leaching during the summer fallow period.