The remobilization of storage nitrogen (N) is affected by growth characteristics of young pear trees. Aboveground parts of young pear trees grafted on P. betulifolia grew more vigorously than that on dwarfing rootstocks. Therefore, the remobilization of storage N within young pear trees on vigorous rootstocks may be different from that on dwarfing rootstocks. A ¹⁵N tracing experiment, including six groups of one-year-old pear trees grafted on vigorous rootstocks in 2016, was conducted to investigate the mobilization of storage N from 2016 to 2018. Results indicated that about 44%, 31.4% and 24.6% of storage N remobilized in new growth was derived from the trunk, shoots and roots, respectively. Most of storage N remobilized in new organs were supplied by trunks and shoots. About 82.2% of storage N withdrawn from senescent leaves were recovered in the trunk and shoots during autumn. The aboveground parts played a more important role than roots in the cycling process of storage N in young pear trees. However, as compared with young pear trees on dwarfing rootstocks, more storage N recovered in new organs were supplied by roots of that on vigorous rootstocks, due to vigorous growth and more nutrient requirement of aboveground parts.

A field experiment was conducted in 2023 and 2024 in Beijing, China, to investigate effects of soil water stress, applied before the fruit ripening stage, on the fruit total soluble solid accumulation and cracking of jujube trees. The experiment consisted of two variation factors: (a) irrigation levels (MDI and SDI, applied 80% and 50% of the irrigation volume, respectively) and (b) growth stages (stage 1, before the fruit enlargement stage, and 2, before the fruit ripening stage). The two irrigation levels were applied at each growth stage in a 2 × 2 factorial arrangement, plus a control treatment receiving 100% irrigation volume, resulting in five treatments per replicate. The findings indicated that pre-enlargement stage water stress enhanced the accumulation of total soluble solid content within fruits, which subsequently promoted faster fruit growth in from the early- to mid-August period. However, by late August, both the total soluble solid content and fruit growth rates had declined, thereby mitigating the risk of fruit cracking. During the fruit enlargement stage, the fruit total soluble solid content in SDI-2 increased by approximately 24% by the end of August compared to the control, leading to lower osmotic potential and higher turgor pressure during the following ripening stage. As skin growth ceased, high turgor pressure caused fruit cracking at the following ripening stage. The SDI-2 treatment demonstrated a fruit cracking rate approximately 1.5 times higher than that of the control. Pearson correlation analysis also indicated that fruit cracking was positively correlated with total soluble solids accumulated in August. Meanwhile, the yield of SDI-2 was reduced about 18%. Therefore, the adequate soil moisture during the fruit enlargement stage was crucial to minimize jujube fruit cracking and economic losses. Meanwhile, the deficit irrigation applied during the pre-enlargement stage could effectively conserve water resources and mitigate the occurrence of extensive jujube fruit cracking.

Background and aims Plastic mulching (PM) can improve soil aggregate stability and microbial activity, thereby preventing soil degradation in crop fields, which are different from the conditions in the orchard. However, little is known about the response of surface-soil microbial and structural stability to PM applied in orchards. Methods An experiment was conducted from 2017 to 2020 in a pear orchard. Two treatments consisted of no mulching and plastic (black woven polypropylene fabric) lying under a pear tree canopy. Results Results showed that the soil microbial biomass carbon content (MBC), organic carbon content (SOC), and ratio of MBC/SOC of PM treatment declined by 49.2%, 13.4%, and 41.3%, respectively. In particular, the significant decline in ratio of MBC/SOC indicated that SOC content would decrease in the future. Mean weight diameter and geometric diameter of soil aggregates in PM treatment decreased by approximately 20%, as compared with no mulching. The decrease in MBC, SOC and soil aggregates stability under PM were mainly resulted from the reduction in root exudate production and root-associated symbionts, causing by the absence of grass roots. These can be proved by the soil gas exchange and concentration. Soil respiration and mineralization were decreased by PM, but soil oxygen concentration at 10 cm depth in PM were improved, due to the oxygen consumed by microbial in no mulching treatment and low gas exchange at this depth. Conclusions Unlike the crop field, protecting the surface soil in orchard from degradation under long-term plastic mulching application is worth considering.

Soil water flux is a key parameter for understanding water and heat transport processes in the vadose zone. The heat pulse technique (HPT) has shown considerable potential for predicting soil water flux. Traditional three-needle probe methods, the maximum dimensionless temperature difference (MDTD) method and the ratio of downstream to upstream temperature increases (Ratio) method, can only measure water flux along the probe alignment. To enhance the applicability of the HPT method, the five-needle probe with vector addition allows for the measurement of soil water flux in any direction within the plane perpendicular to the needles. However, its applicability across different soil textures remains unclear. The objective of this study was to evaluate the applicability of the MDTD and Ratio methods when combined with vector addition across different soil textures. Experimental results show that the vector MDTD and Ratio methods improve water flux measurement accuracy compared with traditional three-needle methods, confirming the reliability of the vector HPT approach. Specifically, the mean absolute percentage error (MAPE) of the vector MDTD method decreased by 1.69%, 1.04%, and 1.80% in sand, sandy loam, and silt loam, respectively, compared with the traditional MDTD method. In contrast, the MAPE of the vector Ratio method varied by +8.83%, −6.73%, and −18.20% in the same soils, relative to the traditional Ratio method. Examining the root mean square error (RMSE) of each method yields a similar conclusion. Similarly to traditional HPT methods, the measurement accuracy of the vector HPT approach is influenced by soil texture, water flux range, and probe spacing. Notably, because the vector HPT method involves four probe spacings, namely the distances between the heating needle and the temperature-sensing needles, it can exacerbate the instability of the resultant water flux measurements. These findings may facilitate the broader application of the HPT method.