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Salinity stress significantly constrains agricultural productivity and vegetation decline worldwide, particularly in Iran. Potassium, the second most prevalent nutrient in plants, is well known to be essential for cell metabolism. Here, the effects of potassium fertilizer in two biogenic nanoparticles (K-NPs) and conventional (potassium sulfate) forms (0.1 mg/ml) on Melissa officinalis L. under salinity (0, 50, 100, and 150 mM) were investigated. The results demonstrated that stress markers (electrolyte leakage, malondialdehyde, and hydrogen peroxide) increased as salinity levels increased. Plant growth parameters (shoot and root length, fresh and dry weight of shoot and root) and physiological and photosynthetic parameters (stomatal conductance, relative water content, chlorophyll fluorescence, and photosynthetic pigments) were reduced in salinized plants. The highest reduction in fresh weight root, dry weight root, fresh weight shoot, dry weight shoot, root length, and shoot length was recorded under 150 mM NaCl by 30.2%, 51.6%, 30.5%, 24.7%, 26.4%, and 21%, respectively. In contrast, bulk potassium sulfate and K-NPs increased these parameters. Furthermore, K-NPs improved M. officinalis tolerance to NaCl toxicity by enhancing the content of osmolytes such as proline, soluble sugars, and antioxidant enzymes, improving antioxidant contents such as phenols, tannins, anthocyanins, and flavonoids; increasing total protein; and lowering stress markers in plant tissues. Given the results of the physiological, biochemical, and phytochemical parameters obtained from this study, it can be stated that K-NPs, in comparison to the conventional form of potassium fertilizer, exhibit a greater potential to mitigate damages caused by salinity stress in M. officinalis plants.

AIMS AND BACKGROUND: Soil fertility quality index is a useful indicator that helps to improve sustainable land use management and achieve economical yield in agriculture production. The objectives of this study were to evaluate the changes of soil fertility quality between the 1980s and 2000s in different cropping systems and its significance to crop productivity and sustainability. METHODS: We collected all published data on crop yields and soil parameters from 58 long-term experiments in three typical double-cropping systems in China, including maize-wheat (M-W), rice-rice (R-R) and rice-wheat (R-W) cropping systems, and selected seven fertilizer treatments in each experiment, including inorganic fertilizer [nitrogen and phosphorus fertilizer (NP), nitrogen and potassium fertilizer (NK), phosphorus and potassium fertilizer (PK) and balanced mineral fertilizer (NPK)], combined NPK with farmyard manure (NPKM) or crop straw (NPKS), and no fertilizer application (served as control). For comparison, an integrated fertility quality index (IFQI) was used to estimate the variations in soil fertility in different cropping systems. Moreover, the mean production variability index (PVI, %) in each cropping system was calculated to evaluate the stability of crop production. RESULTS: Over cropping systems, the averaged relative yields of PK, NK and NP ranged from 38.0 to 97.4 %, while the mean yields can be increased by 2.4–5.1 % in NPKM, compared to NPK. The mean yields were similar between NPK and NPKS for maize and wheat crops, but the yield was increased by 4.3–10.0 % in NPKS. Among the different treatments, the highest variability of cereal productivity was obtained in NK, PK or Control, while the lowest value was mostly recorded in NPKM or NPKS in these three cropping systems. Relative to the control, the IFQIs in fertilization treatments were increased by 9.4–150.0 %, 6.2–41.5 % and 1.3–17.5 % in M-W, R-W and R-R systems, respectively (except for PK treatment in R-R system). However, changes of IFQI in topsoil differed among fertilizer treatments, and greater increases existed in the treatments receiving organic residues (NPKM and NPKS). CONCLUSIONS: The increase in crop yield is exponentially correlated with the increased IFQI over treatments in three cropping systems. Over the treatments and systems, production variability among years is shown to be negatively, linearly related to IFQI (P < 0.001). Therefore, the high grain yield and low production variability can be simultaneously achieved by increasing soil fertility in all three cropping systems.

The present study aims to assess the influences of long-term crop straw returning and recommended potassium fertilization on the dynamic change in rice and oilseed rape yield, soil properties, bacterial and fungal alpha diversity, and community composition in a rice–oilseed rape system. A long-term (2011–2020) field experiment was carried out in a selected paddy soil farmland in Jianghan Plain, central China. There were four treatments with three replications: NP, NPK, NPS, and NPKS, where nitrogen (N), phosphate (P), potassium (K), and (S) denote N fertilizer, P fertilizer, K fertilizer, and crop straw, respectively. Results showed that long-term K fertilization and crop straw returning could increase the crop yield at varying degrees for ten years. Compared with the NP treatment, the long-term crop straw incorporation with K fertilizer (NPKS treatment) was found to have the best effect, and the yield rates increased by 23.0% and 20.5% for rice and oilseed rape, respectively. The application of NPK fertilizer for ten years decreased the bacterial and fungal alpha diversity and the relative abundance of dominant bacterial and fungal taxa, whereas continuous straw incorporation had a contradictory effect. NPKS treatment significantly increased the relative abundance of some copiotrophic bacteria (Firmicutes, Gemmatimonadetes, and Proteobacteria) and fungi (Ascomycota). Available K, soil organic matter, dissolved organic carbon, and easily oxidized organic carbon were closely related to alterations in the composition of the dominant bacterial community; easily oxidized organic carbon, dissolved organic carbon, and slowly available K were significantly correlated with the fungal community. We conclude that long-term crop straw returning to the field accompanied with K fertilizer should be employed in rice-growing regions to achieve not only higher crop yield but also the increase in soil active organic carbon and available K content and the improvement of the biological quality of farmland.

This study investigated the effects of soil-applied, foliar-applied, and nano-potassium fertilization on nutrient uptake and content in maize (Zea mays L.). A pot experiment was conducted to evaluate conventional and nano-K fertilizers at recommended, half, and double rates, as well as integrated combinations. The results demonstrated significant improvements in plant nutrient content under all potassium treatments compared with the unfertilized control. Nitrogen content increased markedly, with the highest level observed in the double-rate nano-potassium treatment (T9, 1.77%), representing a 131% increase over the control. Integrated and combined fertilization treatments (T6–T8) also enhanced nitrogen content (1.667–1.71%, 117–123% increase). Phosphorus content was highest under nano-potassium at the recommended rate (T4, 0.611%), and combined or integrated treatments further improved P uptake. Potassium accumulation peaked under conventional soil application (T2, 2.18%), while nano-potassium treatments provided a more balanced nutrient uptake and improved efficiency. The observed enhancements in nutrient content are attributed to the synergistic roles of potassium in activating enzymatic processes, improving root development, and facilitating nutrient translocation, which collectively optimize nitrogen and phosphorus assimilation. These findings highlight the potential of nano-potassium fertilizers, especially when applied in integrated strategies, to increase nutrient-use efficiency and reduce total fertilizer inputs. The study supports the application of nano-K as a sustainable alternative to conventional potassium sources, offering opportunities for improved maize productivity and sustainable nutrient management.

PurposeUrease inhibitors provide a simple solution to mitigate ammonia loss from fertilized soil. Consumption of bulk blend fertilizers and compound fertilizers were increased in recent year and its enhanced efficiency and stabilized techniques were urgently required. However, it is essentially unknown if and how the efficacy of urease inhibitors is influenced by the inclusion of phosphorus (P) and potassium (K) fertilizers with urea.Materials and methodsA laboratory study was therefore conducted to assess the impact of P and K (bulk blend scenario: combing urea with di-ammonium phosphate (DAP); compound fertilizer scenario: nitrogen (N)-P-K proportion as 16-16-16 (CN16) or 32-0-6 (CN32)) and additionally the impact of fertilizer storage duration and temperature on the efficacy of two different urease inhibitors NBPT and Limus® in reducing ammonia volatilization following application to soil.Results and discussionBoth urease inhibitors significantly reduced ammonia loss from urea regardless of storage temperature and time. However, mixed storage of urea and DAP with urease inhibitors significantly decreased the efficacy of NBPT and Limus® in reducing ammonia loss. Ammonia loss increased exponentially with DAP addition rate and with storage time of the mixture. Storage at a higher temperature (30 °C compared with 20 °C) also reduced the efficacy of the inhibitors. Adding magnesium sulfate (MgSO4) to urea plus Limus® significantly mitigated the negative effect of DAP mixed storage on the efficacy of Limus® regardless of storage temperature and time. The urease inhibitors did not significantly reduce ammonia loss from CN16, but were effective for reducing ammonia loss from CN32.ConclusionsThe efficacy of urease inhibitors was compromised by P fertilizer. Urease inhibitor inclusion in the production of CN32, urea, and its blends (DAP + MgSO4) are recommended as an effective means of reducing the environmental cost causing by intensive agricultural production.

Potassium (K) is the most important element for fruit quality improvement. This study aimed at determining the best K fertilizer type that can promote grape growth and nutrient uptake. Specifically, four types of K fertilizers (complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate) were applied to grapevines grown in plastic pots, and then their effects on grape growth and nutrient uptake were explored. Results showed that the complex fertilizer and potassium nitrate treatments increased the biomass of the grapevine plants, whereas the other fertilizers had no significant effects on the biomass. Only the potassium nitrate treatment increased the contents of photosynthetic pigments in grapevine leaves. The complex fertilizer and potassium nitrate treatments increased the total N content in the grapevine plants to some extent, whereas the other fertilizer treatments decreased the total N content to some extent. It was also evident that all four K fertilizers increased the total P and K contents in the grapevine plants. Compared to the control, the complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate treatments increased the scion total P content by 20.18%, 9.77%, 12.52%, and 30.81%, respectively, and increased the scion total K content by 15.37%, 8.41%, 20.15%, and 26.48%, respectively. In addition, correlation and grey relational analyses showed that the rootstock stem total N content, rootstock root biomass, and soil alkali-hydrolyzable N concentration were the top three indicators most closely associated with the scion total N content, whereas the rootstock root total P content, soil available P concentration, and rootstock stem total P content were the top three indicators most closely associated with the scion total P content. Additionally, the rootstock root total K content, soil available K concentration, and rootstock root total P content were the top three indicators most closely associated with the scion total K content. Overall, the different K fertilizers can all promote the uptake of P and K by grapevine plants, and the potassium dihydrogen phosphate fertilizer is the best choice.

Potassium is an essential nutrient element for potato production. However, there is little research on how the base/topdressing ratio of potassium fertilizer affects plant growth. Therefore, in this 2-year (2022–2023) study, we used Longshu 7 as the experimental material and conducted a pot experiment. Under the condition of total potassium application of 5.4 g/plant, the potassium fertilizer base/topdressing ratios were as follows: CK (10:0), T1 (2:8), T2 (4:6), T3 (6:4), and T4 (8:2). We investigated the effects of potassium fertilizer application on dry matter quality, endogenous hormones, photosynthetic fluorescence characteristics, carbon and nitrogen metabolism and yield in potato. The results of the study demonstrated that potassium topdressing had a positive effect on plant growth through the optimization of endogenous hormone content and regulation of cell elongation. In addition, potassium application can enhance the activity of enzymes related to carbon and nitrogen metabolism, promote photosynthesis, improve the transport efficiency of photosynthetic products and enhance the dry matter quality of tubers. Among all the potassium topdressing treatments, the T2 treatment exhibited a significant difference. However, it is important to note that an excessive increase in the base/topdressing ratio of potassium fertilizer may have detrimental effects on the levels of gibberellin A3 (GA 3 ) and starch content. Based on Pearson correlation analysis, it was determined that the activities of sucrose synthase (SuSy), sucrose phosphate synthase (SPS) and glutamine synthetase (GS) play a significant role in influencing the dry matter quality of potato tubers. These findings provide valuable insights into the importance of these factors in potato production. Overall, the results of this study highlight the significance of maintaining an appropriate ratio of base to topdressing of potassium fertilizer. This optimal ratio ensures the efficient assimilation and utilization of nitrogen and carbon, ultimately serving as a valuable theoretical foundation for effective potassium fertilizer application in potato production.

Potassium is an essential nutrient for crop growth and plays a critical role in regulating water metabolism, facilitating photosynthate transport, and improving agricultural product quality. The precise management of potash fertilizer inputs is therefore vital for enhancing agricultural productivity and promoting sustainable resource use. Using panel data for 31 provinces in China from 2000 to 2024, obtained from the China Statistical Yearbook, this study integrates the Tapio decoupling model, stochastic frontier analysis (SFA), fixed-effects models, and an XGBoost–BiLSTM hybrid model to investigate the dynamic relationship, utilization efficiency, and driving mechanisms of potash fertilizer inputs and grain production. The results indicate that the relationship between potash fertilizer inputs and grain production has shifted from an expansive negative decoupling state—characterized by faster growth in fertilizer inputs than in output—to a strong decoupling state, where fertilizer inputs decline while grain production continues to increase. This transition exhibits a clear spatial gradient, with improvements from eastern to northeastern and central regions. Potassium use efficiency (KUE) shows a steady upward trend, with significant regional heterogeneity, characterized by higher efficiency in the south, lower efficiency in the north, and notable differentiation in western regions, largely driven by climatic and soil variations. Despite these improvements, substantial potential for reducing fertilizer inputs remains across provinces. Potash fertilizer inputs exert a significant positive effect on grain production, while the cultivation of potassium-intensive crops, such as sugar crops, tobacco, and fruits, is a key driver of regional demand. Model projections suggest that from 2025 to 2030, grain production will grow at an annual rate of 1.2–1.5%, while potash fertilizer inputs will decline by 2–4% annually, indicating a transition toward greener agricultural development. These findings highlight the need for region-specific fertilization strategies, optimized fertilizer structures, and improved soil nutrient monitoring systems to ensure food security and sustainability.

A fertilisation experiment, with the aim to determine the effects of different potassium fertiliser rates and their interactions with nitrogen and phosphorus on field-rotation productivity, potassium balance, fertiliser utilization, and changes in the content of potassium in soil, was carried out in Lithuania between 1971 and 2020. The multi-factorial scheme with 45 treatment plots, where seven rates (including zero) of nitrogen, phosphorus, and potassium fertilisers were studied. The experimental treatments during the study period were carried out on winter wheat, spring wheat, spring barley, sugar beet, spring rapeseed, and annual and perennial grasses. It was found that potassium fertilisers were the most effective on agricultural crops when used in combination with other major plant nutrients—i.e., nitrogen and phosphorus. The required balance of potassium (K2O) in the soil was measured, when nitrogen and phosphorus fertilisers were applied together to compensate for potassium removal; when applying low nitrogen (N) (72 kg ha−1) and phosphorus (P2O5) (64 kg ha−1) fertiliser rates, 128 kg ha−1 of potassium fertilisers are required. When using high nitrogen (180 kg ha−1) and phosphorus (160 kg ha−1) fertiliser rates, 160 kg ha−1 of potassium is needed. The highest potassium uptake, reaching 51.6%, was achieved when plants had been fertilised with nitrogen (108 kg ha−1), phosphorus (96 kg ha−1), and potassium (96 kg ha−1). When fertilising with potassium fertilisers alone, the content of plant-available K2O content in the soil increased, whereas with fertilisation with nitrogen and phosphorus combined K2O content is decreased, except in the plots where the plants had been fertilised with potassium fertiliser at rates of 128 kg ha−1 and higher. Due to the influence of fertilisers, the amount of non-exchangeable potassium in the soil also increased, but relatively little compared to the amount of available potassium content. Thus, one of the main conditions for the effective use of potassium fertilisers is ensuring optimal plant nutrition with other nutrition elements, especially nitrogen and phosphorus.

The impact of potassium fertilization on disease resistance in Korla fragrant pear trees was evaluated under drip irrigation to determine the optimal application rate. Seven- to eight-year-old trees were subjected to four K treatments: the control (K0, 0 kg/hm) and applications of 75 (K75), 150 (K150), and 225 kg/hm2 (K225). Disease resistance indices in current-year shoots and old branches were assessed throughout growth stages, and correlations with branch mineral contents were analyzed. The K75 treatment significantly increased branch Ca and Mg contents and enhanced flavonoid and lignin contents and PAL activity relative to K0. The K150 treatment markedly raised N, P, K, Fe, Mn, and Cu contents, as well as flavonoid, lignin, soluble sugar, PPO, and PAL levels, with optimal effects on flavonoids and old branch PAL activity. The K225 treatment mildly reduced Ca and Mg but strongly elevated total phenols, flavonoids, lignin, soluble sugars, PPO, and PAL, exerting the greatest influence on total phenols, soluble sugars, PPO, and current-year shoot PAL. K rates were significantly correlated with disease resistance indices. Branch mineral contents showed highly significant correlations with resistance indices and yield, but resistance indices were not significantly associated with yield. Potassium directly modulated resistance indices, with mineral elements exerting more pronounced effects in current-year shoots. Application of 150 kg/hm K is proposed as the optimal rate to improve disease resistance, mineral nutrition, tree vigor, survival, and yield in 7–8-year-old Korla fragrant pear orchards.