Four temperature treatments were studied in the climate controlled growth chambers of the Georgia Envirotron: 25/20, 30/25, 35/30, and 40/35 °C during 14/10 h light/dark cycle. For the first growth stage (V3-5), the highest net photosynthetic rate (P _N) of sweet corn was found for the lowest temperature of 28–34 µmol m⁻² s⁻¹ while the P _N for the highest temperature treatment was 50–60 % lower. We detected a gradual decline of about 1 P _N unit per 1 °C increase in temperature. Maximum transpiration rate (E) fluctuated between 0.36 and 0.54 mm h⁻¹ (≈5.0–6.5 mm d⁻¹) for the high temperature treatment and the minimum E fluctuated between 0.25 and 0.36 mm h⁻¹ (≈3.5–5.0 mm d⁻¹) for the low temperature treatment. Cumulative CO₂ fixation of the 40/35 °C treatment was 33.7 g m⁻² d⁻¹ and it increased by about 50 % as temperature declined. The corresponding water use efficiency (WUE) decreased from 14 to 5 g(CO₂) kg⁻¹(H₂O) for the lowest and highest temperature treatments, respectively. Three main factors affected WUE, P _N, and E of Zea: the high temperature which reduced P _N, vapor pressure deficit (VPD) that was directly related to E but did not affect P _N, and quasi stem conductance (QC) that was directly related to P _N but did not affect E. As a result, WUE of the 25/20 °C temperature treatment was almost three times larger than that of 40/35 °C temperature treatment.

Bioorganic fertilizers can alleviate (a) biotic stresses and sustainably increase crop yields. The effect of bioorganic fertilizers on the rhizosphere bacterial community of Panax notoginseng and soil metabolism remains unknown. Here, we tracked the changes in the soil physicochemical properties, bacterial microbiota responses, and soil metabolic functions after the addition of a bioorganic fertilizer in a P. notoginseng field. The application of a bioorganic fertilizer reduced the soil acidification, improved the organic matter, and increased the contents of the total/available soil nutrients. Soil amendment with a bioorganic fertilizer significantly affected the structure of the rhizosphere bacterial community, leading to the enrichment of specific bacterial consortia such as Rhodanobacter, Arthrobacter, Sphingomonas, Devosia, Pseudolabrys, Luteimonas, Lysobacter, Nitrosospira, and Nakamurella. Previously, many of these genera have been associated with nutrient cycling, plant productivity, and disease suppression. Metabolome analysis further highlighted that the bioorganic fertilizer treatment significantly reduced phenolic acids and flavonoids and enhanced organic acids, saccharides and alcohols, and amino acids. This result indicates a high survival of bacterial microbiota in the rhizosphere and an availability of nutrients for P. notoginseng growth. This work showed that the application of bioorganic fertilizers significantly improves soil health status, alters soil metabolic functions, and stimulates a specific subset of rhizosphere microbiota for nutrient cycling and disease protection in P. notoginseng.

Net CO₂ uptake rates (P _N) were measured for the vine cacti Hylocereus undatus and Selenicereus megalanthus under relatively extreme climatic conditions in Israel. Withholding water decreased rates and the daily amount of CO₂ uptake by about 10 % per day. Compared with more moderate climates within environmental chambers, the higher temperatures and lower relative humidity in the field led to a more rapid response to drought. The upper envelopes of scatter diagrams for P _N versus temperature for these Crassulacean acid metabolism species, which indicate the maximal rates at a particular temperature, were determined for both night time CO₂ uptake in Phase I (mediated by phosphoenolpyruvate carboxylase, PEPC) and early morning uptake in Phase II (mediated by ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBPCO). As stem temperature increased above 13 °C, the maximal P _N increased exponentially, reaching maxima near 27 °C of 12 and 8 μmol m⁻² s⁻¹ for Phases I and II, respectively, for H. undatus and 6 and 4 μmol m⁻² s⁻¹, respectively, for S. megalanthus. Based on the Arrhenius equation, the apparent activation energies of PEPC and RuBPCO were 103 and 86 kJ mol⁻¹, respectively, for H. undatus and 77 and 49 kJ mol⁻¹, respectively, for S. megalanthus, within the range determined for a diverse group of species using different methodologies. Above 28 °C, P _N decreased an average of 58 % per °C in Phase I and 30 % per °C in Phase II for the two species; such steep declines with temperature indicate that irrigation then may lead to only small enhancements in net CO₂ uptake ability.

The phenomenological expression showing crop yield to be directly dependent on water deficiency, under saline conditions, has encouraged a continued focus on salinity as a viable approach to increase crop yields. This work reassesses crop response to availability of saline soil water ASW in two stages (A) Develop a simple approach suggesting that permanent wilting point (WP) increases under high saline soil water tension and relative yield of Lettuce (Lactuca sativa L., var longifolia Lam., cv. Nevada) and maize (Zea mays L., cv. Jubilee sweet) decrease. (B) Using a deterministic numerical soil water model to validate the theory on Bermuda grass of golf courses. The experimental plots were established in the North Negev, Israel (Sweet corn) and the Algarve, Portugal (Lettuce and Bermuda grass covering the golf courses). Sprinkler irrigation and line source techniques were used for water application, creating a saline gradient under a precise irrigation water distribution. Two salinity empirical models were tested (Mass and Hoffman MH and van Genuchten–Gupta vGG). Their empirical models were modified and instead of soil electrical conductivity of irrigation water (EC_e) we used wilting point (WP) and RASW to follow the changes in relative yield. The validation was conducted with theoretical soil plant atmosphere water (SPAW) to predict the results on golf courses. It is concluded that an alternative S-shaped response model provides better fit to our experimental data sets. Modified MH model (Yr = Y/Ymax = a ∗ (ASW–threshold’s constant) revealed that a single dimensionless curve could be used to express yield—salinity interference when represented by varying ASW. The vGG model: vGG can represent salt tolerance of most crops, by using varying wilting point of average root zone salinity, at which the yield has declined by 50%. The abscissa of both models was based on WP rather than the standard soil electrical conductivity (EC_w). The correlation between the experimental data and WP or relative available soil water (RASW) was acceptable and, therefore, their usefulness for prediction of relative yield is acceptable as well. The objectives of this study were: 1. To develop a simple model describing the effect of salinity through soil water availability on crop production; 2. To replace the standard varying soil electrical conductivity EC_e used by MH and vGG models by two soil parameters (at wilting point- θ_wp and at field capacity θ_fc) in order to describe the relationship between them and relative yield. 3. Validate the new model with respect to independent salinity on Golf courses and a mathematical deterministic model.

Canopy nitrogen (N) status relates strongly to canopy chlorophyll content and the strength of green color. Proximal photograph by RGB camera was used to select green features that has the potential to assess N content at leaf of plant as a function of its the greenness. We proposed the development of it as a tool for sensing nitrogen content in spring wheat (Triticum aestivum). Image processing algorithm was programed calibrated and validated wheat %N%N. Nitrogen uptake =%N × canopy dry matter was harvested and calculated using simulated dry matter by DSSAT model. The data replicated laboratory measurements. A linear Lab vs Camera model displayed a unit slope with r² = 0.93. Increase of dry matter was successfully surrogated by days after emergence and used as abscissa for inverse logistic model of critical nitrogen level. It decreased gradually from about 6% to 2% as days after emergence increased from 0 to 110 days. Maximum N uptake calculated from photo and laboratory was 324 Kg ha⁻¹ and 318 Kg ha⁻¹ respectively suggesting insignificant difference. Physiological N-use efficiency (i.e., canopy weight/N weight) was 52 and 78 kg canopy dry weight per 1 kg N for early and late-ripening cultivars, respectively. The determination of N application based on the smartphone photograph proved to be useful by saving on time and expenses for growers who have access to smartphones and can use them for N application and management.