Precise irrigation management of grapevines in greenhouses requires a reliable method to easily quantify and monitor the grapevine water status to enable effective manipulation of the water stress of the plants. This study evaluated the applicability of crop water stress index (CWSI) based on the leaf temperature for diagnosing the grapevine water status. The experiment was conducted at Yuhe Farm (northwest China), with drip-irrigated grapevines under three irrigation treatments. Meteorological factors, soil moisture contents, leaf temperature, growth indicators including canopy coverage and fruit diameter, and physiological indicators including SPAD (relative chlorophyll content), stem water potential (${\phi }_s$), stomatal conductance (g_s), and transpiration rate (E) were studied during the growing season. The results show that the relationship between the leaf-air temperature difference (T_c-T_a) and the plant water status indicators (${\phi }_s$, g_s, E) were significant (P < 0.05), and the relationship between g_s, E and T_c-T_a was the closest, with R² values ranging from 0.530–0.604 and from 0.545–0.623, respectively. CWSI values are more easily observed on sunny days, and it was determined that 14:00 BJS is the best observation time for the CWSI value under different non-water-stressed baselines. There is a reliable linear correlation between the CWSI value and the soil moisture at 0–40 cm (P < 0.05), which could provide a reference when using the CWSI to diagnose the water status of plants. Compared with the T_c-T_a value, the CWSI could more accurately monitor the plant water status, and above the considered indictors, g_s has the greatest correlation with the CWSI.

More frequent and more intense heat waves and greater drought stress will occur in the future climate environment. Short-term extreme heat and drought stress often occur simultaneously after winter wheat anthesis, which has become the major constraint threatening future wheat yield. In this study, short-term heat, drought and their combination stress were applied to wheat plants after anthesis, and all wheat plants were restored to the outdoor normal temperature and full watering after stress treatment. The aim of the current study was to evaluate the role of nitrogen (N) in modulating the effects of post-anthesis short-term heat, drought and their combination stress on photosynthesis, N metabolism-related enzymes, the accumulation of N and protein and growth, as well as on the yield and water (WUE) and N use efficiency (NUE) of wheat after stress treatment. The results showed that compared with low N application (N1), medium application (N2) enhanced the activities of nitrate reductase (NR) and glutamine synthase (GS) in grains under post-anthesis heat and drought stress alone, which provided a basis for the accumulation of N and protein in grains at the later stage of growth. Under post-anthesis individual stresses, N2 or high application (N3) increased the leaf photosynthetic rate (A_n), PSII photochemical efficiency and instantaneous WUE compared with N1, whereas these parameters were usually significantly improved by N1 application under post-anthesis combined stress. The positive effect of increased A_n by N application on growth was well represented in a higher green leaf area, aboveground dry mass and plant height, and the variation in A_n can be explained more accurately by the N content per unit leaf area. Short-term heat, drought and combined stress after anthesis resulted in a pronounced decrease in yield by reducing grain number per spike and thousand kernel weight. The reduction in NUE under combined stress was higher than that under individual heat and drought stress. Compared with N1, N2 or N3 application significantly prevented the decrease in yield and NUE caused by post-anthesis heat and drought stress alone. However, N1 application was conducive to improving the productivity, WUE and NUE of wheat when exposed to post-anthesis combined stress. The current data indicated that under short-term individual heat and drought stress after anthesis, appropriately increasing N application effectively improved the growth and physiological activity of wheat compared with N1, alleviating the reduction in yield, WUE and NUE. However, under combined stress conditions, reducing N application (N1) may be a suitable strategy to compensate for the decrease in yield, WUE and NUE.

Soil degradation has exacerbated the gap between crop yield and increasing food demands, and unreasonable field management is one of the main reasons for soil degradation. As a classic orchard soil management mode, living grass mulch can effectively change the hydrothermal environment and soil physicochemical properties of the ‘soil–vegetation–atmosphere’ microclimate of apple orchards. However, these improvement effects are mainly affected by climatic conditions, mulch methods, vegetation varieties and continuous grass-growing years. To evaluate the different effects of living grass mulch and the main influencing factors on soil physicochemical properties of apple orchards in China, in this study, we conducted a meta-analysis using data from 53 peer-reviewed publications to carry out soil quality assessment. The results showed that compared with clear tillage, continuous living grass mulch in apple orchards could improve soil function and performance by about 56% and increase soil enzyme activities by 10–120%, on average, whereas the soil organic matter under the effect of artificial grass and natural grass significantly increased by 29.6% and 14.6%, respectively. Artificial grass in temperate and warm, temperate, semi-humid climate regions had a greater overall improvement effect on the soil physicochemical environment than natural grass. Clover was found to be the most suitable for planting in apple orchards in temperate, semi-humid climate regions, whereas both clover and ryegrass were the best choices in warm, temperate, semi-humid climate regions. The interaction effects of different soil physicochemical properties in apple orchards in warm, temperate, semi-humid climate regions were greater than those in warm, temperate, arid climates and temperate, semi-humid climate regions. The response sensitivity of soil organic matter, organic carbon, urease, catalase, sucrose and cellulase to the living grass mulch effect of apple orchards was greater than that of other soil properties.

Drip irrigation technology has obvious advantages in solving the shortage of agricultural water. The demand for using low-quality water sources for irrigation is becoming urgent. Research on the physical blockage formation has become the main part of solving the emitter blockage in China. The purpose of this study is to investigate the blockage characteristics of the emitters in the drip irrigation system with a low-quality water source and to provide some basis for the anti-clogging measures. Therefore, we configured different concentrations (1.8 g/L, 2.8 g/L, 3.8 g/L) and different particle sizes (0–0.054 mm, 0.054–0.075 mm, 0.075–0.1 mm) of low-quality water sources and carried out drip irrigation tests. The holistic and local characteristics of the physical blockage occurrence and distribution were compared under the sand-laden water source irrigation, then the structure and element composition of the blockage material were analyzed. The results show that the clogging characteristics are related to the emitter types, sediment content, and sediment particle size. The higher sediment concentration means that the single emitter is more likely to be blocked completely, and the whole clogging development is short and quick. However, at lower sediment concentration treatments, the probability of complete clogging decreases, and the clogging process is uniform and slow. The blockage position of large flow channel emitters (E1) appears at the head and middle of the drip irrigation tape, and the internal blockage usually occurs at the inlet. The small size channel emitters (E2 and E3) are concentrated in the head and end of drip irrigation tape, and the internal blockage usually occurs in the low-speed zone of the labyrinth channel such as the inlet fence. The internal blocked material is the accumulation structure formed by sediment particles and the coupled precipitation aggregate formed by the reaction of various chemical ions. Among them, the mixing of large and small sediment particles is more inclined to form a stable blocking skeleton structure.

Early heat and drought priming may increase the plant’s ability to resist later drought and heat stress. However, it remains unclear whether combined heat and drought priming can enhance the acclimation of plants to later combined stress by improving physiological activities. In this study, maize seedlings were first pre-exposed twice to heat, drought, and a combination of stresses followed by recovery, and then subjected to six days of more severe stresses. A considerable reduction in photosynthetic pigment content, stomatal size, and photosynthesis was observed under heat and drought conditions, and the changes in the above indicators were amplified under combined stress conditions. Stress priming improves antioxidant defense and cellular osmoregulation, as indicated by improved superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione reductase (GR), and ascorbate peroxidase activities, as well as elevated soluble sugar (SS) and proline (Pro) contents. Lower superoxide anion and malondialdehyde contents and injury index in the primed seedlings demonstrated the mitigation of oxidative stress. ROC analysis revealed that SOD and POD had considerable reliability in determining that maize seedlings were experiencing heat stress (AUC = 0.941–0.971); GR and SS were capable of accurately monitoring drought stress that was being experienced by plants (AUC = 0.919–0.958); and SOD, GR, and Pro had more capability for detecting the combination of heat and drought stress (AUC = 0.907–0.958). Collectively, the primed seedlings exhibited better performance than the non-primed seedlings, exhibiting stronger stress acclimation supported by an effective antioxidant defense system and osmoregulatory function.