Objective  An optimized fertilization for sweet potato farming that could simultaneously reduce fertilizer usage, increase land fertility, and regress soil acidifying was formulated.

Method  Based on the results accumulated from years of field experiments conducted in the major sweet potato producing areas of Fujian province, a fertilization program applying organic and chemical fertilizers and soil conditioners were proposed. Effects of partially replacing chemicals with organic fertilizers and adding magnesium hydroxide and/or oyster shell conditioner on soil fertility and acidification at farmlands of varied fertility and productivity were analyzed.

Result More than other replacement rates, substituting 25% conventionally applied inorganic compounds with organic fertilizers had demonstrated an increased tuber yield by 13.5% in sweet potato cultivation field trials. The increase varied depending upon the fertility and productivity of the site. The application appeared to be more effective on barren soils, as it raised the yield by 4.1% on the highly productive lands, 7.2% on the intermediately productive lots, and 18.5% on lowly productive fields. For remedying acidification on land, the addition of agricultural magnesium hydroxide at a rate of 300 kg·hm⁻² or oyster shells at 1 500 kg·hm⁻² in soil not only raised the pH but also the yield of sweet potatoes grown on it. On the field where 25% chemicals were replaced by an organic fertilizer along with 300 kg·hm⁻² of magnesium hydroxide application, a significantly increased tuber yield of 4 641.7 kg·hm⁻² and soil pH by 0.49 over the conventional fertilization was achieved.

Conclusion  Replacing 25% of chemical fertilizer with an organic one and adding agricultural magnesium hydroxide at a rate of 300 kg·hm⁻² or oyster shells at 1 500 kg·hm⁻² for fertilization significantly reduced the fertilizer usage, improved the efficiency, and mitigated the soil acidification in sweet potato farming.