Integrated fertilization matches mineral nutrients in tropical potato fields

Potato plants supplied with a blend of half-rate mineral nitrogen, vermicompost and rock phosphate inoculated with the phosphate-solubilizing bacterium Klebsiella variicola accumulated nitrogen, phosphorus and potassium at levels statistically comparable to those receiving full mineral fertilizer in a two-season field study in Mozambique’s tropical highlands. The experiment covered three contrasting sites and 11 fertilization treatments, offering evidence that combining mineral, organic and microbial inputs can maintain nutrient acquisition in acidic soils where phosphorus fixation limits fertilizer performance. The result applies to the tested potato cultivar, soils, seasons and inputs; it does not establish that the same formulation will produce equivalent outcomes elsewhere.

Researchers established randomized complete block trials at Ntengo-wa-Mbalame in Tsangano, Rinze in Angónia and the CITTA Research Centre during the 2022/23 and 2023/24 growing seasons. Each site included 11 treatments with three replications, and plants were destructively sampled at 28, 40, 70 and 120 days after planting. These sampling points represented vegetative growth, tuber initiation, tuber bulking and physiological maturity, allowing the investigators to follow nutrient accumulation rather than relying only on an end-of-season comparison. The potatoes were cv. Mondial, planted at 41,666 plants per hectare, while zinc and copper sulfate were applied uniformly to prevent micronutrient deficiencies.

The soils were acidic, with calcium chloride pH values of 5.4 at Ntengo-wa-Mbalame and 4.6 at both Rinze and CITTA. The experimental sites included Chromic Abruptic Alisols, Chromic Luvisols and Pellic Calcic Vertisols, and the authors identified potential aluminum toxicity and strong phosphorus fixation as central challenges. Against that background, the most closely matched treatment, T7, supplied 60 kilograms of mineral nitrogen per hectare, 1.9 tonnes of vermicompost per hectare, and Bio-Rock P containing Minjingu rock phosphate inoculated with strains of K. variicola. It also included mineral potassium and sulfur, with phosphorus supplied through the inoculated rock phosphate. Full mineral fertilization supplied 120 kilograms of nitrogen, 92 kilograms of P₂O₅, 120 kilograms of K₂O and 45 kilograms of sulfur per hectare.

Vermicompost made from maize and soybean residues, cattle manure and vermicomposting by Eisenia foetida was incorporated seven days before planting. Bio-Rock P was placed in planting holes at planting, and half of the mineral nitrogen was incorporated at planting while the remainder was applied 30 days later. In laboratory assays, the two bacterial strains produced available phosphorus concentrations of 159.81 and 218.81 milligrams per liter in calcium phosphate assays at pH 4.51 and 3.99, respectively, compared with 0.098 milligrams per liter in the control. With Minjingu rock phosphate, recovered phosphorus reached 55.86 and 49.35 milligrams per liter, exceeding the control’s 29.09 milligrams per liter. These laboratory results supported the biological component of the field treatment but were not themselves evidence of field yield gains.

Nutrient accumulation generally followed quadratic curves with coefficients of determination around 0.95, although the authors emphasized that the estimated peaks were model-based because only four sampling dates were available. In the more favorable first season, modeled maximum nitrogen and potassium accumulation generally occurred about 98 to 115 days after planting. Estimated phosphorus peaks occurred between 108 and 113 days after planting at two sites. Potassium had the greatest modeled peak magnitude, reaching 10.23 grams per plant at CITTA in the first season. T7 consistently belonged to the highest statistical group for nutrient accumulation and achieved nitrogen and phosphorus recovery efficiencies statistically equivalent to the complete mineral treatment, showing that the integrated package maintained nutrient acquisition under the conditions tested.

Secondary macronutrients and micronutrients also responded to the integrated treatments. Modeled calcium, magnesium and sulfur peaks ranged from 77.5 to 121.4 days after planting, depending on site, nutrient and season. T7 and T8 ranked in the highest statistical group for calcium, with estimated peaks as high as 1.20 grams per plant, and for sulfur, with peaks reaching 0.27 grams per plant. Iron showed the largest micronutrient accumulation, including an estimated first-season peak of 165.49 milligrams per plant at CITTA. Copper was unusual because its accumulation followed a linear pattern at nearly all sites and seasons, with a detectable inflection point only at Ntengo in the second season. The authors cautioned that uniform copper-based fungicide use may have contributed to measured copper through surface contamination rather than plant uptake alone.

Seasonal conditions strongly altered the results. Analysis of variance identified effects of year, treatment and growth stage, as well as interactions between year and treatment and between year and stage. Across the sites, nutrient accumulation in the first season was 35% to 45% greater than in the second. Rainfall and temperature patterns were associated with greater late-blight pressure from Phytophthora infestans in the second season, when fungicide applications were increased to weekly intervals. Because disease incidence and severity were not quantitatively measured, the statistical analysis could not directly quantify late blight as an explanatory variable. Nevertheless, total biomass was lower at the final sampling, and fitted nitrogen and potassium peaks at Ntengo occurred earlier, at about 87 days after planting, rather than beyond 110 days.

The study also evaluated apparent recovery efficiency, agronomic efficiency, physiological efficiency and internal utilization efficiency for nitrogen and phosphorus, then combined these measures with yield through principal component analysis. The first two components explained 68.55% of total variation in the first season and 65.29% in the second. In the second season, internal nitrogen efficiency increased from 342.02 to 460.68 kilograms per kilogram as absolute accumulation declined. The authors interpreted this as possible preferential partitioning of absorbed nutrients toward tubers under stress, but cautioned that the earlier fitted peaks could partly be mathematical artifacts of reduced biomass at 120 days. A separate potassium peak of 127.4 days after planting at CITTA in the second season was explicitly an extrapolation beyond the experiment and was not an observed maximum.

For farmers, the practical significance of the findings is that nutrient supply from vermicompost and biologically mobilized rock phosphate can be combined with reduced mineral nitrogen without measurably compromising nutrient acquisition relative to full mineral fertilization in these trials. The authors also argue that such combinations could lower dependence on costly mineral inputs, although the experiment did not provide a complete economic assessment of treatment profitability. The approach should not be read as a recommendation that fertilizer applications can be reduced indiscriminately: T7 remained a balanced package that included mineral potassium and sulfur, and its performance depended on local soil conditions, rainfall, crop management and disease pressure. Future work should use denser sampling intervals, larger plots, additional locations and seasons, and longer-term measurements of soil carbon and microbial communities. Until then, the strongest conclusion is that the tested integrated treatment can match full mineral nutrient acquisition in acidic tropical highlands while supplying nutrients through complementary biological, organic and mineral pathways.

Subject of Research: Integrated mineral, organic and microbial fertilization for nutrient uptake in acidic-soil potato cultivation

Article Title: Sustainable intensification of potato production: nutrient uptake kinetics and accumulation dynamics under integrated fertilization in acidic tropical highlands

Article References: Sande, T. J., Alovisi, A. M. T., Tindwa, H. J., Semoka, J. M., & Shitindi, M. (2026). Sustainable intensification of potato production: nutrient uptake kinetics and accumulation dynamics under integrated fertilization in acidic tropical highlands. Frontiers in Agronomy, 8, 1980417. https://doi.org/10.3389/fagro.2026.1980417

Image Credits: AI Generated

DOI: 10.3389/fagro.2026.1980417

Keywords: potato, integrated nutrient management, acidic soils, nutrient uptake, vermicompost, rock phosphate, phosphate-solubilizing bacteria, late blight, Mozambique, tuber bulking, Sustainable, intensification