Essential Role of Potassium in Apple and Its Implications for Management of Orchard Fertilization

Towards Sustainable Productivity of Greenhouse Vegetable Soils: Limiting Factors and Mitigation Strategies

Greenhouse vegetable production has become increasingly important in meeting the increasing global food demand. Yet, it faces severe challenges in terms of how to maintain soil productivity from a long-term perspective. This review discusses the main soil productivity limiting factors for vegetables grown in greenhouses and identifies strategies that attempt to overcome these limitations. The main processes leading to soil degradation include physical (e.g., compaction), chemical (e.g., salinization, acidification, and nutrient imbalances), and biological factors (e.g., biodiversity reduction and pathogen buildup). These processes are often favored by intensive greenhouse cultivation. Mitigation strategies involve managing soil organic matter and mineral nutrients and adopting crop rotation. Future research should focus on precisely balancing soil nutrient supply with vegetable crop demands throughout their life cycle and using targeted organic amendments to manage specific soil properties. To ensure the successful adoption of recommended strategies, socioeconomic considerations are also necessary. Future empirical research is required to adapt socioeconomic frameworks, such as Science and Technology Backyard 2.0, from cereal production systems to greenhouse vegetable production systems. Addressing these issues will enable the productivity of greenhouse vegetable soils that meet growing vegetable demand to be sustained using limited soil resources.

Study on the Bioactive Constituent and Mineral Elements of the Tibetan Medicine E'seguo from Different Regions of Ganzi Prefecture, China

The Tibetan medicinal fruit E'seguo originates from two species, Malus toringoides (Rehd.) Hughes and Malus transitoria (Batal.) Schneid, both unique to the Hengduan Mountains. These species are predominantly found in high-altitude regions of Ganzi Prefecture, Sichuan Province, particularly in the Xianshui River and Yalong River basins. Malus toringoides (Rehd.) Hughes is far more abundant in both resource quantity and distribution compared to Malus transitoria (Batal.) Schneid. However, the nutritional and medicinal differences between the two remain unclear, which significantly impacts the development and utilization of E'seguo resources. This study aimed to measure the mineral content, nutritional components, and medicinal properties of E'seguo from 12 different regions of Ganzi Prefecture to explore the quality differences between these two species and across different regions. ICP-MS (Inductively Coupled Plasma Mass Spectrometry) was used to determine the mineral content, ultraviolet-visible spectrophotometry and potentiometric titration to analyze nutritional indicators, and HPLC (High-Performance Liquid Chromatography) to measure the medicinal components L-malic acid and 2-O-β-D-glucopyranosyl-L-ascorbic acid (AA-2βG). Results indicate that Malus transitoria (Batal.) Schneid contains higher levels of K, Ca, Zn, Mg, and Cu compared to Malus toringoides (Rehd.) Hughes, which has higher Fe and Mn content. Malus toringoides (Rehd.) Hughes from the Kangding and Litang regions showed the highest mineral content, with mineral elements primarily influencing polysaccharide levels, according to Mantel analysis. Nutritional and medicinal analyses revealed that Malus toringoides (Rehd.) Hughes outperformed Malus transitoria (Batal.) Schneid in all metrics except for the sugar-acid ratio. Given the mineral content and taste, Malus transitoria (Batal.) Schneid is better suited for consumption, while Malus toringoides (Rehd.) Hughes has superior medicinal properties, making it more appropriate for medicinal use. In the Malus transitoria (Batal.) Schneid regions, both Luhuo and Daofu are in the Xianshui River basin, with Daofu County producing the higher quality fruit. Among the nine Malus toringoides (Rehd.) Hughes regions, the M10 (Tuoba Township, Ganzi County) near the Yalong River had the highest overall score, followed by M7 (Yade Township, Luhuo County) and M6 (Keke, Xiala Tuo Town, Luhuo County), both of which are near the Xianshui River. In summary, Malus transitoria (Batal.) Schneid generally has higher mineral content, but Malus toringoides (Rehd.) Hughes has larger fruit and higher medicinal value, making the latter more suitable as a medicinal resource. At the same time, the medicinal quality of Xianshui River fruit was higher in the two watersheds of Malus toringoides (Rehd.) Hughes.

Impacts of N-P-K-Mg Fertilizer Combinations on Tree Parameters and Fungal Disease Incidences in Apple Cultivars with Varying Disease Susceptibility

Adequate mineral fertilization helps to ensure optimal tree growth, fruit development, and predictable yield of apple trees. This 7-year study (2016-2022) aims to investigate the effect of nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg) fertilizer combinations (NP, NPK, NPKMg, and control) on eight parameters (trunk cross-sectional area-TCSA; fruit yield-FY; number of fruit per tree-FNT; crop load-CL; fruit diameter-FD; fruit weight-FW; fruit scab incidence-FSI; and powdery mildew incidence on shoot-PMIS) on the cultivars (cvs) 'Golden Reinders' (disease susceptible) and 'Pinova' (scab and mildew tolerant). In the 7-year period, TCSA values continuously increased for both cultivars over the years. Fertilizer treatments showed significant differences on TCSA but the effect varied greatly annually among fertilizer treatments. Fertilizer treatments had increasing effects on FY and FNT in 2018 and 2022, on CL in 2018, on FD in 2018 and 2019, and on FW in 2016 and 2018 in both cultivars compared to the control treatment. FSI values were the lowest in the NPKMg treatment for cv. 'Golden Reinders' in 2016, 2017, and 2022; for cv. 'Pinova' in 2016; PMIS values for cv. 'Golden Reinders' in 2017, 2018, 2021, and 2022; and for cv. 'Pinova' in 2018. Correlation and regression analyses revealed strong and significant (p = 0.05) relationships between FNT versus (vs.) TCSA, FNT vs. FY, FW vs. TCSA, CL vs. FY, FW vs. FD, and FSI vs. FW. In conclusion, our study showed that multiyear application of fertilizer combinations can successfully increase TCSA and yield parameters as well as reduce fungal disease incidences, especially on the disease-susceptible cultivar in sandy soil with moderate fertility, under Central-European continental climate conditions.

Integrated soil-fruit-climate management system to improve apple production stability

Unstable agricultural systems, such as unreliable fruit production, threaten global food security and could negatively impact human nutrition. However, methods of maintaining a stable fruit supply have received little attention. Therefore, this study explored the impact of a systematic service model on the establishment of an integrated soil-fruit-climate management (ISM) approach and stabilization of apple yield based on a fixed-effects model using sample data from Fuji apple farmers in China for six consecutive years (2016-2021). The results showed that the systematic service model dramatically improved the adoption of ISM-based technology. By 2021, the rate of ISM technology adoption among farmers reached 84.4 %, especially pendulous branch-fruiting technology and Osmia pollination, which increased by 82.2 % and 37.8 %, respectively, compared to that in 2016. With the adoption of the ISM approach, apple yields and tree loadings stabilized over time. For example, the yield change rate and tree loading change rate were 14.8 % and 7.3 % lower, respectively, in 2021 than in 2016. We demonstrated through a fixed-effects analysis that the ISM approach exerts a fully mediated effect on the mechanism of action of service measure quantity disclosure, which positively impacted the rate of change in yield and tree loadings. This finding indicated that the six-in-one systematic service model of soil testing, pest and disease diagnosis, course training, meteorological monitoring, on-site guidance, and experimental demonstration established by the Science and Technology Backyard model resolved the information, goal, and hardware gaps that limited the adoption of this technology by farmers and promoted the construction of an integrated soil-fruit-climate management approach, which in turn has stabilized the apple production system.

The Features of Potassium Dynamics in 'Soil-Plant' System of Sour Cherry Orchard

This research aimed to study interannual and seasonal dynamics of different potassium compounds in orchard soil and the potassium status of sour cherry trees affected by the application of nitrogen and potash fertilizers. Afield experiment was started in 2017 at an orchard located in the forest-steppe zone of the Central Russian upland. Urea and potassium sulfate were applied to the soil once a year in early spring with rates from N30K40 to N120K160 kg/ha. The content of exchangeable and water-soluble potassium compounds was determined in soil samples five times throughout the growing season from May to September 2018-2020. The content of non-exchangeable potassium was determined twice, in 2017 and 2020. The interannual and seasonal dynamics of plant-available potash in unfertilized soil depended on the weather patterns and the uptake of potassium by trees. In the unfertilized plots, the first signs of potassium nutrition insufficiency appeared, such as low leaf and fruit potassium status and a decrease in the non-exchangeable potassium reserves in the20-40 cm soil layer. The annual fertilization led to the gradual accumulation of exchangeable potassium in the root zone. The accumulation was accelerated with increasing rates. When the exchangeable potassium level in the topsoil reached 200 mg/kg, the intensification of both the seasonal fluctuations in potash content and the potash leaching into the depths of the soil occurred in all treatments. In the conditions of our experiment, one-time treatments with superfluous potassium rates (over 80 kg/ha) did not provide an enlarged stock of plant-available potash in the soil but caused unreasonable losses of it due to leaching. An increase in fertilizer rates was not essential for normal metabolic processes and did not manifest itself as an increase in potassium content in leaves and fruits or as an increase in yield.

A non-K+-solubilizing PGPB (Bacillus megaterium) increased K+ deprivation tolerance in Oryza sativa seedlings by up-regulating root K+ transporters

Potassium is one of the principal macronutrients required by all plants, but its mobility is restricted between soil compartments. Numerous studies have shown that Plant Growth Promoting Bacteria (PGPB) can facilitate nutrient uptake. The present work examined the effects of the PGPB (Bacillus megaterium) on rice plants subjected to potassium deprivation. To study only direct effects of B. megaterium, we first checked its lack of capacity to solubilize soil K. Rice plants were provided with 1.5 mM K (100%) or 0.015 mM K (1%) and growth related parameters, nutrient concentrations and gene expression of K⁺ transporters were determined. After two weeks, the 1% K treatment reduced growth of non-inoculated plants by about 50% compared with the 100% K treatment. However, there was no effect of reduced K nutrition on growth of inoculated plants. The reduction in growth in non-inoculated plants was accompanied by a similar reduction in K⁺ concentration in both roots and leaves and an overall 80% reduction of the plant potassium concentrations. In inoculated plants a 50% reduction occurred only in leaves. The expression of the K⁺ transporters HKT1;1, 1;2, 1;5, 2;2, 2;3 and 2;4 was up-regulated by the inoculation of B. megaterium under K deprivation conditions, explaining their higher K tissue concentrations and growth. Thus, the bacterial strain improved plant potassium nutrition without affecting K⁺ availability in the soil. The results demonstrate the potential of this bacteria for using as a biofertilizer to reduce the amount of potassium fertilizers to be applied in the field.

Prediction of Potassium in Peach Leaves Using Hyperspectral Imaging and Multivariate Analysis

Hyperspectral imaging (HSI) is an emerging technology being utilized in agriculture. This system could be used to monitor the overall health of plants or in pest/disease detection. As sensing technology advancement expands, measuring nutrient levels and disease detection also progresses. This study aimed to predict three different levels of potassium (K) concentration in peach leaves using principal component analysis (PCA) and develop models for predicting the K concentration of a peach leaf using a hyperspectral imaging technique. Hyperspectral images were acquired from a randomly selected fresh peach leaf from multiple trees over the spectral region between 500 and 900 nm. Leaves were collected from trees with varying potassium levels of high (2.7~3.2%), medium (2.0~2.6%), and low (1.3~1.9%). Four pretreatment methods (multiplicative scatter effect (MSC), Savitzky–Golay first derivative, Savitzky–Golay second derivative, and standard normal variate (SNV)) were applied to the raw data and partial least square (PLS) was used to develop a model for each of the pretreatments. The R2 values for each pretreatment method were 0.8099, 0.6723, 0.5586, and 0.8446, respectively. The SNV prediction model has the highest accuracy and was used to predict the K nutrient using the validation data. The result showed a slightly lower R2 = 0.8101 compared with the training. This study showed that HSI could measure K concentration in peach tree cultivars.