Deep fertilization effects on potato production and GHG emissions depend on soil C:N:P-enzyme interactions: Evidence from a 4-year study

Abstract

Context and problem

As potato is one of the four major food crops, enhancing yield is crucial, particularly when considering the mitigation of environmental impacts. Deep fertilization represents a potential strategy for efficient nutrient utilization; however, its specific on potato yield, quality and greenhouse gas emissions require further elucidation.

Methods

We conducted a four-year field experiment (2020–2023) using potatoes as the test crop. We investigated the impacts of four fertilization depths (D5, 5 cm, control with locally conventional fertilization depth; D15, 15 cm; D25, 25 cm; D35, 35 cm) on soil C, N, and P content and ratios, enzyme activity, greenhouse gas emissions, potato growth, yield, and quality.

Results

Deep fertilization significantly increased the soil SOC:TN, SOC:TP, MBC:MBN, and SIC:SIN ratios, while decreasing the MBC:MBP, MBN:MBP, and POC:PON ratios. In addition to soil catalase, the activities of invertase, urease and phosphatase were closely related to the soil C:N:P ratio. Specifically, deep fertilization increased soil invertase and phosphatase activities but decreased catalase and urease activities. Correlation analysis showed that N₂O and CO₂ emissions were positively correlated with soil urease activity, whereas CH₄ uptake and CO₂ emissions were negatively correlated with soil phosphatase and sucrase activities, respectively. Furthermore, increase of soil phosphatase activity enhanced the leaf area index, net photosynthetic rate, and dry matter accumulation of potato while reducing stem lodging, ultimately improving yield and quality. Among these treatments, D25 achieved the highest improvements in large potato rate (16.4 %) and yield (11.5 %), while simultaneously resulting in high tuber quality in starch (42.5 %), reducing sugar (52.7 %), protein (33.4 %), and vitamin C (31.9 %) content. In addition, its greenhouse gas emission intensity was also at the lowest level (decreased by 32.7 %).

Conclusions

Deep fertilization affects enzyme activity by altering soil C:N:P ratios, thereby promoting potato production and reducing greenhouse gas emissions. In this region, fertilization depths of 15–25 cm exhibited distinct advantage in terms of yield enhancement, whereas depths exceeding 35 cm were more effective in reducing emissions.