Search Results (16)

Global warming has increasingly reduced winter chill accumulation in traditional fruit-growing regions, disrupting dormancy release and bloom synchrony in deciduous fruit crops such as peach (Prunus persica). To evaluate adaptation potential under subtropical conditions, a three-year field study was conducted in central Taiwan using two low-chill cultivars, ‘Tainung No.4 Ruby’ (~100 chilling units, CU) and ‘Tainung No. 7 HongLing’ (~77 CU). Our results demonstrate that both cultivars produced long shoots (>34 nodes), completed vegetative growth by October, and reached natural leaf fall by mid-November. Nonlinear Gompertz and Logistic models accurately described shoot elongation dynamics and growth cessation. Flowering began in mid-January for ‘Tainung No. 7 HongLing’ and mid-February for ‘Tainung No. 4 Ruby’. Seasonal chill accumulation strongly influenced the onset of flower budbreak between apical and basal buds: in the milder 2023–2024 winter (~120 CU), apical–basal onset lags were wider (22 days in ‘Tainung No. 7 HongLing’), whereas in the colder 2024–2025 winter (~280 CU), these lags shortened (14 days). Notably, ‘Tainung No. 4 Ruby’ maintained a consistent apical–basal onset lag between seasons, indicating greater positional stability under variable chilling. Field-estimated CU thresholds for flower budbreak exceeded the reported chilling requirements, suggesting reduced chilling efficiency under fluctuating subtropical winter temperatures. These results demonstrate that integrating shoot growth, leaf fall timing, and chill–heat accumulation provides a phenology-informed framework for cultivar selection and orchard scheduling, thereby enhancing climate resilience of peach production in warm-winter regions. Full article

Soil compaction is a critical challenge in perennial fruit production, limiting root growth, water infiltration, and nutrient uptake—factors essential for climate-resilient and sustainable orchard systems. In subtropical Asian pear (Pyrus pyrifolia Nakai) orchards under the annual top-working system, intensive machinery traffic exacerbates subsurface hardpan formation and tree performance. This study evaluated the effectiveness of pneumatic subsoiling, a minimally invasive method using high-pressure air injection, in alleviating soil compaction without disturbing orchard surface integrity. Four treatments varying in radial distance from the trunk and pneumatic application were tested in a mature orchard in central Taiwan. Pneumatic subsoiling 120 cm away from the trunk significantly reduced soil penetration resistance by 15.4% at 34 days after treatment (2,302,888 Pa) compared to the control (2,724,423 Pa). However, this reduction was not sustained at later assessment dates, and no significant improvements in vegetative growth, fruit yield, and fruit quality were observed within the first season post-treatment. These results suggest that while pneumatic subsoiling can modify subsurface soil physical conditions with minimal surface disturbance, its agronomic benefits may require longer-term evaluation under varying moisture and management regimes. Overall, this study highlights pneumatic subsoiling may be a potential low-disturbance strategy to contribute to longer-term soil physical resilience. Full article

The accurate estimation of evapotranspiration ($ET$) and its components are vital for water resource management and irrigation planning. This study models tree transpiration ($T$) and $ET$ for grapefruit, litchi, and mango orchards using light gradient-boosting machine (LightGBM) optimized using the Bayesian hyperparameter optimization. Grounds $T$ and $ET$ for these crops were measured using the heat ratio method of monitoring sap flow and the eddy covariance technique for quantifying $ET$. The Sentinel 2 satellite was used to compute field leaf area index ($LAI$). The modelled data were used to partition the orchard $ET$ into beneficial ($T$) and non-beneficial water uses (orchard floor evaporation—$E_s$). We adopted the 10-fold cross-validation to test the model robustness and an independent validation to test performance on unseen data. The 10-fold cross-validation and independent validation on $ET$ and $T$ models produced high accuracy with coefficient of determination ($R^2$) $\ge$ 0.88, Kling–Gupta efficiency ($KGE$) $\ge$ 0.91, root mean square error ($RMSE$) $\le$ 0.04 mm/h, and mean absolute error ($MAE$) $\le$ 0.03 mm/h for all the crops. The study demonstrates that LightGBM can accurately model the transpiration and evapotranspiration for subtropical tree crops using Sentinel 2 data. The study found that $E_s$ which combined soil evaporation and understorey vegetation transpiration contributed 35, 32, and 31% to the grapefruit, litchi and mango orchard evapotranspiration, respectively. We conclude that improvements on orchard floor management practices can be utilized to minimize non-beneficial water losses while promoting the productive water use ($T$). Full article

Soil health is essential for sustainable agriculture, influencing ecosystem health and orchard productivity of plum orchards. Global challenges such as climate change and soil contamination threaten to affect fertility and food security, requiring sustainable practices. The study assessed the effect of different orchard management practices on soil quality and nutrient distribution in Prunus domestica L. orchard located on the Moldavian Plateau in northeastern Romania under temperate humid subtropical climate conditions. Two systems were analyzed: conventional (herbicide-based) and conservative (cover crop-based). Soil samples (0–20 cm and 20–40 cm) were analyzed for soil organic carbon (SOC), total nitrogen (N_t), available phosphorus (P), and potassium (K). Results showed that conservative management improved soil health by increasing SOC nutrient cycling, mainly through organic matter inputs. Compared to 2022, the effectiveness of phosphorus in the conservative management system significantly increased (by 6%) in 2023, while potassium content decreased (by 30%), suggesting potential nutrient competition or insufficient replenishment under organic practices. SOC levels remained stable, supporting long-term carbon inputs. Conventional management maintained phosphorus and potassium but showed lower SOC levels and higher risks of soil fertility depletion. Strong correlations between SOC and nutrient indicators emphasize the critical role of organic inputs in nutrient mobilization. The findings indicate that cover crops are essential for sustainable soil management by enhancing carbon sequestration and nutrient cycling, thereby supporting the long-term sustainability of agricultural systems. Full article

Phosphate fertilizers are applied to the soil surface, especially in vineyards in production in subtropical regions. Nowadays, phosphorus (P) is not incorporated into the soil to avoid mechanical damage to the root system in orchards. However, over the years, successive surface P applications can increase the P content only in the topsoil, maintaining low P levels in the subsurface, which can reduce its use by grapevines. For this reason, there is a need to propose strategies to increase the P content in the soil profile of established orchards. The study aimed to evaluate the effect of management strategies to (i) increase the P content in the soil profile; (ii) enhance the grape production; and (iii) maintain the grape must composition. An experiment on the ‘Pinot Noir’ grape in full production was carried out over three crop seasons. The treatments were without P application (C), P on the soil surface without incorporation (SP), P incorporated at 20 cm (IP20), P incorporated at 40 cm (IP40), and twice the P dose incorporated at 40 cm (2IP40). The P concentration in leaves at flowering and veraison, P content in the soil, grape production and its components, and chemical parameters of the grape must (total soluble solids, total polyphenols, total titratable acidity, total anthocyanins, and pH) were evaluated. The P concentration in leaves did not differ among the P application modes. The application of P associated with soil mobilization, especially at 20 cm depth, increased grape production. The P application modes did not affect the values of the chemical parameters of the grape must except for the total anthocyanins, which had the highest values when the vines were subjected to 2IP40. Finally, the P application and incorporation into the soil profile was an efficient strategy for increasing the grape production in full production vineyards. Full article

Citrus is a subtropical fruit tree with high water requirements. This study aimed to determine the effects of water deficit on an orange orchard subjected to different water-saving strategies. The study was realised in an orange orchard in a semiarid area by adopting four different water management techniques: 100% crop evapotranspiration (control); SSDI—subsurface sustained deficit irrigation; RDI—regulated deficit irrigation; PRD—partial rootzone drying treatment during five growing seasons. The experimental design foresaw a randomised block design with six replicates per treatment (24 index plants). The results of the study showed that the water-saving strategies reduced irrigation water consumption by 25% (SSDI), 33% (RDI), and 49% (PRD) compared to the fully irrigated treatment without yield reduction, thus increasing water use efficiency. Mineral nutrition of the trees was slightly affected by irrigation treatments; element concentration in leaves was generally in the optimal range; only potassium showed values below the recommended leaf concentrations. Regarding fruit quality parameters, the vitamin C concentration in RDI showed significant differences with a value of 62.7 mg 100 mL⁻¹ compared to 58.5 mg 100 mL⁻¹ in the control. Plants subjected to SSDI and PRD strategies showed increased levels of pulp colour index with significant values of 10 and 9.90, respectively, compared to the control (8.44). By implementing targeted water management, citrus growers could save water and increase the ascorbic acid and sugar concentration in the fruits; anthocyanins also increased but not significantly. These findings open new market opportunities for citrus growers in marginal areas, where they cannot rely solely on producing citrus fruits to remain competitive. Full article

Soil fertility plays a crucial role in crop growth, so it is important to study the spatial distribution and variation of soil fertility for agricultural management and decision-making. However, traditional methods for assessing soil fertility are time-consuming and economically burdensome. Moreover, it is hard to capture the spatial variation of soil properties across continuous geographic space using the conventional methods. As key techniques of digital soil mapping (DSM), spatial interpolation techniques have been widely applied in soil surveys and analysis in recent years, since they can predict soil properties at unknown points in continuous space based on limited sample points. However, further research is needed on spatial interpolation models for DSM in regions with variable climates and complex terrains, which are characterized by strong spatial variation in both environmental variables and soil fertility. In this study, taking a typical hilly area in a subtropical monsoon climate, i.e., Gaozhou, Guangdong Province, China, as an example, the performances of four popular spatial interpolation models (Random Forest (RF), Ordinary Kriging, Inverse Distance Weighting, and Radial Basis Function) for digital soil mapping on available phosphorus (AP) are compared. Based on RF, the spatial variation and its driving factors of the AP of Gaozhou are then analyzed. Furthermore, by selecting three typical truncation lines from different directions, the correlations between environmental variables and AP in different spatial positions are demonstrated. The root mean square error (RMSE) results of the above four models are 32.01, 32.08, 32.74, and 33.08, respectively, which indicate that the RF has a higher interpolation accuracy. Based on the mapping results of RF, the minimum, maximum, and mean values of AP in the study area are 38.90, 95.24, and 64.96 mg/kg, respectively. The high-value areas of AP are mainly distributed in forested and orchard areas, while the low-value areas are primarily found in urban and cultivated areas in the eastern and western regions. Vegetation and topography are identified as the key factors shaping the spatial variations of AP in the study area. Furthermore, the spatial heterogeneity of the influence strength of altitude and EVI is revealed, providing a new direction for further research on DSM in the future, i.e., spatial interpolation models considering the spatial heterogeneity of the influence of environmental variables. Full article

Alterations of soil characteristics frequently accompany adaptations of pristine areas to different land uses, and these shifts have an impact on the overall ecosystem. Soil carbon stores and atmospheric CO₂ emissions are directly affected by those adaptations in farming management and land usage. To comprehend the mechanisms involved in the carbon pool, this study was conducted in a subtropical region by considering six contiguous land uses; pasture, rice land, kiwi orchard, tea land, woodland, and uncultivated land. A CO₂ trap was used to quantify CO₂ emissions for six weeks, and the obtained data were used to analyze CO₂ respiration. In comparison to other land uses, the pasture and woodland showed the best results in soil microbial respiration (SMR), significantly higher than other land uses, with values of 2561.2 and 2334.8 mg CO₂-C kg⁻¹ soil, respectively. Tea land and uncultivated land demonstrated considerably increased microbial metabolic quotients (MMQ) compared to other land uses. Whereas with an increase in soil depth, the MMQ significantly increased in tea and uncultivated lands, other land uses did not show significant changes with depth. Compared to other land uses, pasture, and forest areas boosted soil organic carbon (SOC) and microbial biomass carbon (MBC) both in the top and subsoil. It is reasonable to assume that the amount of SOC and MBC in the soil significantly dropped when the land was converted from pasture and woodland to other land uses. Full article

Nitrogen (N) effect on crop yield depends on several factors such as soil type, climatic characteristics and orchard management, including plant density and N fertilization. These variables can be used to develop yield prediction models, which are scarce in the horticulture sector. This study aimed to evaluate the effect of nitrogen fertilization, orchards and cultivars and to predict the yields of ‘Royal Gala’ and ‘Fuji Suprema’ apples cultivated in a subtropical climate under different soil N availabilities. During the four seasons, nitrogen fertilization was applied a rates of 0, 25, 50, 100 and 150 kg N ha⁻¹ year⁻¹ for ‘Royal Gala’ and ‘Fuji Suprema’ apples located in southern Brazil. Yield, average fruit weight and leaf and fruit pulp N concentration were evaluated. Yield prediction models were developed based on the following variables: concentration of N in leaves and fruits, air temperature, chilling units, relative humidity and rainfall. “Cultivar” was the variable responsible for the greatest variation of yield, followed by “years/season”, and then the “orchard management. The N rates applied in the four seasons did not predict crop yield. In the model, “orchard” was the greatest determinant for leaf N concentration, and “season” was the main determinant for fruit-pulp N concentration. Mathematical model (3), based on leaf and fruit pulp N concentration, and certain climatic variables (minimum air temperature, annual rainfall and chilling hours < 7.2 °C) had the greatest potential for predicting yield in orchards of ‘Royal Gala’ and ‘Fuji Suprema’. Full article

All tropical and subtropical areas of the world are suitable for citrus cultivation. In managing fertilizer application efficiency in orchards, variable-rate technology (VRT) has been demonstrated to be an important element. This article aims to study the significance of variable-rate fertilization for citrus in the arid region of Pakistan. The NPK was calculated before the application of the variable-rate fertilizer. The plant height and stem girth were determined before and after fertilizer application. The preliminary results revealed that the stem girth performed significantly better than the plant height after applying fertilizer by VRT. The preliminary results showed a significant difference in the fruit yield between the VRT and uniform-rate fertilizer application. Full article

Plant-parasitic nematodes are one of the main biotic factors limiting agricultural production worldwide, with root-knot nematodes (Meloidogyne spp.) being the most damaging group. This study was conducted to evaluate the efficacy of soil microbiomes, associated with various subtropical fruit trees, on the management of a Meloidogyne enterolobii population. Of 14 soil microbiomes tested for nematode suppression, 9 samples in the first experiment and 10 samples in the repeat experiment had significantly (p ≤ 0.05) lower numbers of eggs and J2 compared to the untreated control. The highest nematode suppression was recorded for SA12 extracted from a papaya orchard with a 38% reduction in the nematode population density. In addition, the presence of some bacteria (Bacillus aryabhattai, B. funiculus and B. simplex) and fungi (Metarhizium marquandii, Acremonium sp. and Mortierella sp.) was correlated to a higher suppression potential in some samples. Substantial variations were observed for the diversity of bacterial and fungal isolates among the samples collected from various crop hosts and regions. This suggests that the nematode suppression potential of different soil microbiomes highly depends on the abundance and diversity of fungal and bacterial strains present in the soil. The study confirmed that among all variables, soil dryness, pH, Fe, Zn, organic matter, altitude, and crop cultivar strongly influenced the soil microbial composition. Full article

In managed orchards, fertilization brings out not only high productivity expectations but also severe environmental pollution. Because economic profit takes priority over environmental cost, increasing amounts of fertilizer have been used in mature subtropical Torreya grandis orchards. However, given the magnitude of global nitrogen deposition, it’s worth considering whether heavy fertilizer treatment is necessary. To elucidate the balance between T. grandis nutrient demands and fertilizer supply, we determined the C, N, and P concentrations of foliar and soil ([C], [N], [P]) at 9 orchards undergoing long-term fertilizer treatments in two scenarios of N and N + P addition with different intensity. After documenting the dynamic variation of plant growth, nutrients characteristic, and the corresponding resorption efficiency, we found that excessive N addition interfered T. grandis’ sensibility to P availability in this N-enrichment area, leading to an increasing foliar [P] and resorption efficiency (PRE) and decoupling plant C:N:P ratios. As a result, enhanced fertilizer supply failed to improve carbon accumulation, plant growth, and yield effectively. These results demonstrate that extra fertilization in the N-saturated study area highly reduced the economic and ecological efficiency of fertilizers. Thus, our research suggests that N addition in the studied orchards should be rejected, and we recommend organic management as a more conducive method to achieve sustainable development. Full article

European consumers have perceived that papaya fruits produced in subtropical areas (the Canary Islands and Mediterranean regions) do not have the desired quality at certain periods of the year. Thus, the development of technical and management strategies to optimize the yield and the quality of the fruit requires crop phenology studies. Meteorological variables (air temperature, relative humidity, and photosynthetically active radiation) and morphological characteristics (plant height, leaf emission rate, and leaf area) were recorded throughout the crop cycle. All the leaves and fruits were labeled in their anthesis week to calculate the source–sink ratio and to study the development and quality of the fruits. Data were collected in three commercial orchards representing two different types of systems, greenhouse and screenhouse, and two different regions: two plastic cover greenhouses located in the south (SP) and in the north (NP) of Tenerife, and one 40-mesh net screenhouse in the north of the island (NN). The selection of these cultivation systems and locations was made deliberately, so that the ambient variables within these crop protection structures were different throughout the cultivation cycle in order to better fit the model construction. The results suggested that in order to maintain good fruit quality, better environmental control is necessary inside the greenhouses and the screenhouse. Monitoring variables such as the growing degree days, the photosynthetically active radiation, and the number of fruits per plant leaf area ratio provided useful information for papaya production management in the Canary Islands and other subtropical areas, allowing farmers to predict harvest and fruit quality. Full article

Peach (Prunus persica) is an economically important temperate fruit crop due to its edible fruits. Due to the need to develop new varieties better adapted to climate change, it is of great interest to find germplasm adapted to warmer conditions, such as those found in the Canary Islands. Peach was an important crop during the last century in one of those islands (La Palma), but its cultivation has been abandoned in recent years. Currently, commercial production is relict and isolated trees are relegated to family orchards with little management. With the objective to characterize and prevent the loss of local varieties of this crop, peach trees were sampled along La Palma. A total of 89 local peach accessions were prospected and analyzed with 10 single-sequence repeat (SSR) loci, which permitted 28 different genotype profiles to be detected. These genotypes were compared to 95 Spanish peach landraces conserved in an ex situ collection, and 26 additional samples from eight different countries. Results showed that the peach genetic diversity found in La Palma was low. In addition, a relation between La Palma samples and other Spanish peaches was observed, which could indicate the arrival of genetic material from the Iberian Peninsula and subsequent intercrossing and local selection of the genotypes more adapted to the subtropical climate of the island. The population structure reflects a grouping of the samples based on fruit type and geographic origin. Full article

Water scarcity in many semi-arid agricultural areas, in particular for the Mediterranean basin, is promoting changes in irrigated agriculture, with alternative strategies being introduced for water-use optimization. The coast of Granada and Malaga (Southeast Spain) is an economically important area for subtropical fruit cultivation. This intensively irrigated agriculture is characterized by requiring extra amounts of water and the adoption of sustainable practices to improve agricultural water management. A two-season experiment was conducted to assess (1) the water use in terraced cherimoya (Annona cherimola Mill. cv. Fino de Jete) orchards under conventional and organic production systems with drainage lysimeters, and (2) the impact on fruit yield and nutritional effects between the two considered production systems. Crop coefficient (Kc) values for cherimoya were 0.60–0.66, 0.64–0.71, and 0.48–0.62 at flowering, fruit set, and fruit growth, respectively. Fruit yield was similar in both systems, ranging from 47.1 for conventional to 44.1 kg tree⁻¹ for organic farming, averaging 13.2 and 12.3 t·ha⁻¹, respectively. No differences between these systems were observed in terms of leaf nutrient status, with variations in the N, P, and K contents during the different phenological stages. The N, P, and K lessen during flowering and fruit growth; the highest levels of these nutrients were fixed at harvest. These patterns were the opposite in Ca and Mg, ascribable to the antagonism between K and both Ca and Mg. Thus, these findings highlight the need to establish the optimal use of irrigation water with respect to crop requirements, thereby encouraging sustainable subtropical farming in terraces. Full article