Abstract

Wheat is one of the most important staple foods worldwide, and the organic substitution for chemical fertilizer has been increasingly receiving attention in wheat planting. However, its impact on nitrous oxide (N2O) emissions and ammonia (NH3) volatilization from the wheat fields, as well as on the heavy metal [Nickel (Ni), Copper (Cu), Zinc (Zn), Cadmium (Cd), and Lead (Pb)] contents in the wheat grain is poorly known. A two-year field experiment was performed with two organic manures (sewage sludge compost and pig manure compost) and two substitution ratios (25 % and 50 %) for chemical nitrogen (N) fertilizer during the wheat season. An increasing trend in wheat yield (0.33∼5.9 %) was observed and total N2O emission was significantly decreased by 33∼77 % with partial organic substitution (POS). Therefore, the fertilizer-induced N2O emission factor was highly decreased (0.12∼0.47 % VS. 0.77∼0.92 %). The POS relatively increased NH3 volatilization by 7.9∼17 % (p > 0.05) and as a whole, it played little role in the cumulative N losses of N2O and NH3. The concentrations of Ni, Cu, Zn, Cd, and Pb in wheat grain were 97.4∼335 μg kg−1, 4.51∼5.88 mg kg−1, 28.5∼47.5 mg kg−1, 24.7∼79.6 μg kg−1, and 16.6∼33.4 μg kg−1, respectively. Although POS relatively increased the contents of Cu and Zn, they were all lower than those of the food standard limit for wheat in China. Moreover, the values of metal pollution index (0.39∼0.71) in all treatments were less than one. Our health risk assessment further demonstrated that POS did not pose any health risks. The findings suggest that partial replacement of chemical fertilizer with sewage sludge compost and pig manure compost in the wheat season can significantly decrease N2O emissions while not increasing N losses or compromising yield and its quality.

Full Text
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