{'fraction_non_alphanumeric': 0.023167848699763592, 'fraction_numerical': 0.010874704491725768, 'mean_word_length': 4.5248041775456915, '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}}
Fate of 15N Derived from Composts and Urea In Soils under Different Long-term N Management In Pot Experiments

Understanding of dynamics of N derived from organic N sources in soil is required for the development of sustainable agricultural systems. The aim of this paper is to compare, using pot experiments, the fate of N from urea (UF) and organic N sources such as rice straw compost (RC) and cattle compost (CC) using 15N labeled materials in paddy soil planted with rice. Two soils with a history of long-term applications of chemical fertilizers (LTCN) and organic N sources, i.e. straw compost +soybean cake, (LTON), were also compared. Nitrous oxide emissions were monitored during the growing period. Yield and N uptake of rice were higher in LTON soil than LTCN soil with no significant interaction with N applications. Chemical fertilizer increased yield and N uptake with a recovery rate by rice of 36 to 45%. Nitrogen recovery from RC and CC by rice was less than 10%. When recovery of N in soil was included with that recovered in the plant, 70% and 61% of applied N in the UF treatment was recovered from the LTCN and LTON soils, respectively. In comparison, more than 95% of applied N was recovered in the plant and soil for the RC and CC treatments. There was a sharp increase in N2O emission during the aerated period in nonplanted pots regardless of whether supplemental N was added, and this was associated with the increase in NO3- in soil solution at 0.5 cm depth. There was a much lower N2O emission in planted pots than nonplanted pots with no significant difference among the LTCN and LTON soils or the N treatments. The results indicated that the application of organic N source provided lower N supply to the plant than urea, but also could reduce N loss because of higher retention in the soil. Long-term continuous application of organic N sources enlarged the labile N pool without increasing N2O emission. Nitrous oxide emission was important during the mid-season aerated period from pot experiments and was partly related to the concentration of NO3- and the rate of nitrification.