Dongliang Zhong

Vegetable production in Subtropical China is distinguished by excessive nitrogen (N) fertilization, frequent irrigation, and multiple crop rotations in a single year. The aforementioned variables are closely related to soil nitrous oxide (N₂O) and methane (CH₄) emissions. Hence, we conducted a field trial to measure N₂O and CH₄ emissions using static chamber–gas chromatograph. Four treatments were used: control (CK) with no fertilizer, 100% chemical N fertilization (CN), the conventional 30% chicken manure N plus 70%CN (CMN + CN), and 30% chicken manure biochar N plus 70%CN (CMBN + CN). The annual cumulative N₂O emissions reached 12.4, 63.5, 111.8, and 44.1 kg N₂O-N ha⁻¹ for the CK, CN, CMN + CN, and CMBN + CN treatments, respectively. Compared to the CN and CMN + CN treatments, the CMBN + CN treatment reduced N₂O emissions by 35.9%–65.7%, while it simultaneously increased the total vegetable yield by 16.1% compared to the CN treatment. Seven seasons mean N₂O emission factors are 1.3% for CN, 3.8% for CMN + CN, and 0.9% for CMBN + CN. The CH₄ emission was negligible, ranging from 0.07 kg CH₄-C ha⁻¹ for the CK treatment to 0.8 kg CH₄-C ha⁻¹ for the CN treatment. N₂O emissions peaked under the conditions of an interior chamber temperature of around 31.9 °C and the water-filled pore space (WFPS) of the soil being approximately 60%. Future climate change will intensify, triggering higher N₂O emissions from subtropical vegetable fields. CMB can be one of the best substitutes for direct chicken manure application as a soil supplement because it has a beneficial effect on improving vegetable yield and reducing N₂O emissions in Subtropical China.

Improving yield in potato production with minimal environmental impact is of great significance for China’s potato staple food policy. Previous research has been limited by the absence of regional-scale parameters to evaluate the environmental costs of regional potato production. To address this gap, we utilized the input–output analysis method to offer a thorough estimation of nitrogen (N), phosphorus (P), and potassium (K) inputs and outputs in the potato production stage at a regional scale, leveraging a meta-analysis dataset from plenty of the literature. On this basis, we calculated the virtual N, P, and K factors (VNFs, VPFs, and VKFs) for different potato production regions, under both conventional and optimal management practices. China’s potato production suffered from excessive N and P inputs, while K inputs remained insufficient. Significant spatial heterogeneities were observed for the VNFs, VPFs, and VKFs across different potato production regions. Northeast China and northwest China emerged as the most suitable potato cultivation regions because they demonstrated high potato yields with relatively low inputs and, consequently, lower VNFs and VPFs. Southwest China was the most vital region where targeted efforts could lead to reducing VNF and VPF, thus significantly mitigating environmental N and P losses. In addition to reducing fertilizer inputs, site-specific and whole optimization measures are proposed to lower the environmental costs and promote the sustainable development of potato production.

Based on China’s potato staple food policy, we chose potatoes as a study case to analyze the following indicators—the virtual new nitrogen factor (VNNF), the virtual new phosphorus factor (VNPF), the virtual irrigation-water (IW) factor (VIWF), the virtual total water (IW + precipitation) factor (VTWF), and the virtual greenhouse gas (GHG) emission factor (VCF) of the potatoes consumed by households in the six potato cultivation regions—by reviewing 220 publications from 2000 to 2020. The results showed that the VNNF ranged between 17.8 ± 7.8 and 30.1 ± 17.0 kg N kg⁻¹ N in the consumed potato, the VNPF ranged between 8.4 ± 5.0 and 18.8 ± 11.3 kg P kg⁻¹ P in the consumed potato, the VIWF ranged between 0.3 ± 1.0 and 1.8 ± 1.4 m³ IW kg⁻¹ for the consumed standard yield (except in the three mainly rainfed potato regions), the VTWF ranged between 4.8 ± 2.2 and 9.3 ± 3.7 m³ total water kg⁻¹ for the consumed standard yield, and the VCF ranged between 3.4 ± 1.5 and 5.9 ± 2.4 kg CO₂ equivalent kg⁻¹ for the consumed standard yield, under the conventional practice in the six potato cultivation regions. The normalization score results indicate that the northeast, northwest, southwest, and south of China are relatively more suitable regions in which to plant potatoes, based on the VNNF, VNPF, VIWF or VTWF, and VCF indicators.