نشریه پژوهشهای زراعی ایران
سال بیست و یکم شماره 3 (پیاپی 71، پاییز 1402)

One of the main challenges of modern agriculture in ensuring food security is development of strategies to deal with potential negative impacts and adapt to climate change. To address this challenge, it is crucial to investigate the effects of climatic factors on agricultural production at a spatiotemporal dimension, develop and utilize crop management decision-support tools, and support targeted agronomic research and policy. These endeavors necessitate the availability of accurate and standardized meteorological data.Studying growth degree days and wheat phenology can significantly enhance our understanding of how wheat growth responds to climate change and aid farmers in adapting to and effectively mitigating its influence.

To determine the environmental and management factors affecting the yield of irrigated and rainfed wheat in different regions of North Khorasan province, we investigated the trend of yield changes from 1980 to 2009. Subsequently, we simulated the wheat plant growth stages using the DSSAT model and analyzed the impact of temperature and rainfall changes on yield through panel data analysis. Panel data analysis is a widely used statistical method in social science, epidemiology, and econometrics for analyzing two-dimensional (typically cross-sectional and longitudinal) panel data. This method involves collecting data over time from the same individuals and conducting regression analysis across these two dimensions.

According to the results of this study, 63% of the changes in irrigated wheat yield between the years 1980-2009 can be attributed to environmental factors (temperature and precipitation), while 37% can be attributed to management factors. When comparing environmental parameters, it was observed that the number of temperatures above 30°C (N30TMAX), mean temperature (GSTMEAN), interaction of amount and frequency of precipitation (TPRAT * NPRAT) significantly affect yield (p ≤ 0.05). Bojnord, Shirvan, and Esfarayen regions exhibited significant positive cross-sectional effects in terms of environmental parameters, whereas Farooj, Raz-Jargalan, Maneh Semelghan, and Jajarm regions displayed negative cross-sectional fixed effects.A study examining the critical stages of wheat growth during good years (with high wheat grain yield) and poor years (with low wheat grain yield) revealed that in all weak years, the minimum temperatures fell below the critical level (-11°C). The occurrence of very low temperatures during the early stages of growth and primary leaf production, which is the plant establishment stage, resulted in reduced photosynthesis levels and subsequently severe yield reduction.In all regions and for 100% of the studied years, irrigated wheat in the grain-filling stage experienced temperatures above 30°C, leading to negative cross-sectional effects in Farooj, Raz-Jargalan, Maneh-Semelghan, and Jajarm. The frequency of temperatures above 30°C during the hard dough stage of irrigated wheat was higher than that during the soft dough stage in all regions. Therefore, delaying the planting date from October (the common planting date in the studied areas) would result in conflicts with high temperatures during the soft dough stage and negative temperatures during the primary leaf production stage and plant establishment at the beginning of the growing season, severely reducing yield.

In general, the results of this study demonstrated that implementing effective management methods, particularly selecting the appropriate planting date, can lead to better adaptation of wheat's phenological stages to environmental conditions. This, in turn, has the potential to enhance wheat yield.

Food security is one of the basic needs of any society. Studies have been conducted on the foliar application of elements, especially silicon, calcium, and potassium, to reduce the adverse environmental effects on the physico-mechanical properties of cereals and improve their growth and development in order to maintain food security. Lodging, which is caused by a decrease in the mechanical properties of the plant stem's flexural strength, is characterized by bending or fracture that changes the angle of the grain stem from the vertical position. Due to the important factors involved, an important aspect of performance is directly and indirectly related to the occurrence of fungal diseases and nutrient-related issues affecting the physico-mechanical properties of the plant, such as flexural strength. The efficacy of silicon, calcium, and potassium in addressing these concerns is notable.

This research was conducted at the research farm of the Faculty of Agriculture, Shahroud University of Technology, located in Bastam. The seeds of the Reyhan cultivar, a high-yielding and early spring-type barley plant suitable for regions with mild winters and short springs, were used in this study. Planting operations followed agricultural principles, and irrigation was carried out using atmospheric and ridge methods. The first irrigation took place after planting, and subsequent irrigations were performed aeight-day intervals. Harvesting was done manually at the end of the growing period, specifically 115 days after planting.The experiment followed a factorial design and utilized a randomized complete block design with three replications. On July 11 (115 days after planting), a harvest sample measuring 50 cm2 was taken from each experimental plot, accounting for the margins, to determine the yield.For the barley stem bending test, a three-point bending test was conducted using a material testing machine. The probe applied a loading speed of 5 mm.min-1. A specially designed jaw was used for the barley stem cutting test, taking into consideration the characteristics of the barley plant. The incision test was performed on the second median, and the loading speed was set at 20 mm.min-1.

The main axial stem serves as a storage organ, supporting the filling grains through stock re-transference. A desirable trait is having a higher dry weight in the stem. Among the treatments, foliar application of 6 mM calcium chloride, along with sodium silicate at all three levels and spraying with 12 mM silicon at concentrations of 150 and 300 mg.L-1, showed statistically superior results.Stem diameter is an important attribute related to plant strength, stability, resistance to lodging, and certain fungal diseases. The control plants had a stem diameter of 2.63 mm, which significantly improved with the treatment compounds. Barley stem wall thickness increased significantly with both 150 and 300 mg.L-1 levels of calcium chloride, combined with all three levels of sodium silicate spraying. These factors play a role in determining the ultimate photosynthetic destination, as well as the efficiency and economic production of the target seed cultivar or crop.The results indicated a significant increase in grain yield when simultaneously applying 10 mg.kg-1 silicon with 6 mM calcium chloride, showing a 65% improvement compared to the control. Treatment with three potassium sulfate variations, combined with either 6 or 12 mM calcium chloride, or 12 mM calcium chloride alone, enhanced the flexural strength of the stem by 75%, 60%, and 62%, respectively. Among the treatment compounds studied, the shear strength of barley stems ranged from 2.63 MPa to 5.43 MPa. Plants treated with sodium silicate at concentrations of both 150 and 30 ml.L-1, in conjunction with 6 mM calcium chloride foliar application, exhibited higher shear strength compared to other treatments.

This study demonstrated the tripartite effect of the treatments. The treatment composition derived from a surface area of 300 ml.L-1 of sodium, combined with 6 and 12 mM calcium chloride without potassium sulfate, had the greatest impact on flexural strength and stem diameter.

Covering a staggering 215 million hectares, wheat stands as the world's most extensively cultivated crop plant. Just like its botanical counterparts, wheat operates as an obligate aerobic organism, implying its reliance on absorbing oxygen from the surrounding environment to facilitate growth, proliferation, and the successful completion of its life cycle. Annual instances of waterlogging stress inflict harm upon wheat crops, attributed to inadequate irrigation practices, subpar drainage systems, uneven field leveling, elevated groundwater levels, the presence of unyielding impermeable layers, and bouts of intense, abrupt rainfall. This adverse impact is progressively escalating, potentially influenced by the ongoing shifts in climate patterns. Consequently, the adoption of resilient cultivars and the genetic enhancement of bread wheat assume critical importance. These strategies are aimed at augmenting the wheat's capacity to effectively cope with waterlogging stress, aligning it with the mounting demands of a burgeoning global population.To achieve these goals, it is necessary to understand the factors causing waterlogging stress damage in wheat and to know the mechanisms of tolerance in this plant. The survival of root terminal meristem cells under waterlogging stress conditions is very limited, and their ability to grow again after removing the stress is also restricted. Waterlogging stress leads to the death of primary roots and reduced growth of lateral roots in wheat. However, there is variation among wheat cultivars concerning these traits. Reduced access to oxygen hampers root growth and nutrient absorption, including nitrogen. Consequently, photosynthesis and carbohydrate availability decrease, further restricting root growth.

An outdoor pot experiment was conducted to investigate the effect of waterlogging stress on shoot and root dry matter, as well as some physiological characteristics. The experiment followed a split-plot design based on randomized complete blocks with three replications. The stress was applied at the three-leaf stage, and three control levels were used: no waterlogging stress, mild stress (48 hours of waterlogging stress), and severe stress (120 hours of waterlogging stress) as the main factors. Cultivars and genotypes were also included as secondary factors.During the stress period, the water level was maintained at approximately 5 cm above the soil level. The cultivation took place outdoors in plastic pots. Data analysis was performed using SAS software, and graphs were generated using Excel software. Comparisons between treatments were based on the standard error. After testing different models, the linear regression model was ultimately employed.

Mild and severe waterlogging stress resulted in a significant decrease in shoot dry matter of 14.06% and 38.37%, respectively, across all cultivars and genotypes. Different cultivars and genotypes exhibited varying responses to waterlogging stress. To further understand the reasons for these differences, among the 21 cultivars and genotypes, Mehrgan and Sarang cultivars, as well as ms 93-16 and ms 93-6 genotypes, were selected due to their contrasting tolerance levels and yield potential. These selected cultivars and genotypes were studied to analyze specific root traits.Amidst severe waterlogging stress, a significant 38% reduction in root dry matter and a corresponding 29% decrease in root volume were recorded when compared to stress-free conditions. This closely mirrored the decline evident in shoot dry matter. Evaluation of the susceptibility index during the three-leaf stage unveiled that sole resilience was exhibited by the Aflak cultivar. In contrast, the remaining cultivars and genotypes were stratified into semi-tolerant and semi-susceptible categories.Notably, regression analysis underscored that even brief periods of waterlogging stress ushered in a reduction in dry matter. Furthermore, the elongation of the waterlogging duration magnified this decrease in dry matter, thereby mitigating the disparities across various cultivars and genotypes.

In general, cultivars that were able to sustain higher levels of photosynthetic activity during waterlogging stress demonstrated a lower percentage decrease in dry matter. Although the Mehrgan cultivar experienced a significant reduction in dry matter yield and fell into the semi-sensitive group, it consistently exhibited significantly higher dry matter yield compared to other cultivars and genotypes across all treatments.

In recent decades, the introduction of high-yielding cultivars under optimal conditions has been the main focus of grain research programs. The identification of wheat cultivars that have acceptable yields on different planting dates has been taken into account.

The present split-plot test was performed with three replications in two cropping years, 2016-2017 and 2017-2018. The main factor included three planting dates (October 20, November 20, and December 20 as early, normal, and delayed planting dates), and the sub-factor included six wheat cultivars (Zare with winter growth habits, Heidari, Pishgam, and Alvand with facultative growth habits, and Sirvan and Pishtaz with spring growth habits). The soil was sampled from a depth of 0 to 30 cm before the experiment, and the physical and chemical traits of the soil were determined. Land preparation steps were performed before the experiment. For this purpose, a land area of 1500 m2 was plowed by a reversible plow and then leveled. Fertilizer application was performed based on the soil experiment results as 100 kg.ha-1 of triple superphosphate, 100 kg.ha-1 of potassium sulfate, and 100 kg.ha-1 of urea before planting. The rest of the urea fertilizer (200 kg.ha-1) was applied at the stage of stem emergence and the beginning of anthesis wheat. Iron, zinc, and manganese fertilizers were also used from their sulfate sources at the rate of 0.2%, which were sprayed in two stages at the beginning of stalking and spiking. Each plot was 5 m long and 2 m wide and consisted of 8 planting rows at a distance of 25 cm. A distance of 50 cm was considered between the two sub-plots and 1 m between the two main plots. The required seed for each experimental plot was determined and distributed based on the density of 400 seeds per m2 based on the weight of 1000 seeds of each cultivar. Irrigation was performed immediately after planting. Agricultural care was applied uniformly, including pest, disease, and weed control. In each subplot, 50 cm from the beginning and end of the rows was considered as the margin. All data were subjected to ANOVA using the GLM procedure of SAS (SAS 9.1) and means were compared by using the Duncan test at 5% probability level.

The results showed that delayed planting reduced nutrient uptake and increased the extinction coefficient. Radiation use efficiency on the planting date of December 20 showed a reduction of 27% and 25%, compared to the planting date of October 20 in 2016-2017 and 2017-2018, respectively. Also, on December 20, Sirvan and Pishtaz cultivars with spring growth habits showed lower extinction coefficients and higher photosynthesis rates than winter and facultative cultivars. On October 20 and November 20, the highest grain yield was obtained in cultivars with winter and facultative growth habits. On December 20, the grain yield was higher in cultivars with facultative and spring growth habits than in winter cultivars. Late planting of wheat cultivars with winter growth type, which must receive low temperatures for Vernalization, is very risky. Because delaying planting may lead to a sharp decrease in yield. These negative consequences of the delay in planting may have occurred through disruption of absorption of water, nutrients, and absorption of active photosynthetic radiation. Late cultivation shortens the vegetative growth period and the plant enters the reproductive stage prematurely, and then the plant faces a lack of photosynthetic resources. Also, the grain filling period is faced with drought and heat stress at the end of the season and this final stress causes a sharp decrease in yield.

In general, the delayed planting significantly reduced grain yield, especially in cultivars with winter growth habits. Therefore, it is recommended to use intermediate and spring cultivars for delayed cultivation.

Rice (Oryza sativa L.), as one of the most important cereals, is the main food of more than 50% of the world's population. Excessive use of chemical fertilizers in paddy fields has caused many environmental problems. Therefore, the application of biological fertilizers instead of chemical fertilizers to increase the yield of crops and produce more food is one of the important goals of sustainable agriculture, which is necessary for human life. Bacteria is an example of biological fertilizer used in agriculture, which plays an important role in improving soil structure, improving plant growth, and increasing the quantitative and qualitative yield of crops. Another biological stimulant of plants is amino acids, which can increase plant growth, improve nutrients uptake, and increase grain yield and grain quality of crops. Methionine is the precursor of growth regulators such as auxin, cytokinin, and brassinosteroids and is known as the most important growth-limiting amino acid in plants. Lysine is an essential amino acid that is involved in the germination of pollen grains, chlorophyll synthesis, and crop production. Therefore, the present study aimed to evaluate the effects of different strains of plant growth-promoting bacteria and amino acids on growth, yield, and concentration of nutrients in rice.

The field experiment was arranged as a split-plot in a randomized complete block design with three replications at the farmer's field located in Mazandaran province, Amol during 2019-2020 cropping seasons. In the present research, the plant growth-promoting bacteria at five levels (control or without bacteria [B0], P. agglomerans strain O4 [B1], P. putida strain P13 + P. agglomerans strain P5 [B2], P. koreensis strain S14 + P. vancouverensis strain S19 [B3] and combination of different strains [B4]) as the main factor and amino acids foliar application in four levels (control or without amino acids [A0], methionine [A1], lysine [A2] and methionine + lysine [A3]) as the sub-factor were considered. The plant growth-promoting bacteria at the rate of 100 g.ha-1 and amino acids at a concentration of 2.5 per thousand were applied in this study. At physiological maturity, the growth, yield components, grain yield, and nutrients uptake (NPK) in grain were measured. A combined analysis of variance was performed using SAS software version 9.2. Mean values were compared using least significant difference (LSD) test at 5% probability level.

The outcomes established that the bacteria treatment exerted a notable impact on all examined traits, excluding the count of fertile tillers per hill. Equally noteworthy, the amino acid intervention displayed significance in terms of 1000-grain weight, grain yield, and nitrogen concentration in rice grains. However, the interaction between bacteria and amino acids exhibited no significance across the quantitative and qualitative characteristics of rice. The concurrent utilization of bacteria strains, specifically B4, yielded substantial enhancements in panicle length (24.22 cm), the count of filled grains per panicle (60.30 filled grains), 1000-grain weight (28.52 g), grain yield (5097.50 kg.ha-1), and the amelioration of nutrients concentrations. Notably, nutrients like nitrogen (1.61%), phosphorus (7.04%), and potassium (1.53%) exhibited improvements in rice grains, in comparison to instances involving separate strain applications and the control group. Simultaneous foliar application of methionine and lysine amino acids resulted in maximum 1000-grain weight (26.90 g), highest grain yield (4844.73 kg.ha-1), and production of the greatest nitrogen content in grain (1.40%). In the present research, the increase in grain yield by combined application of different bacteria strains might be due to enhancing growth, improving yield components such as 1000-grain weight and filled grains number per panicle, and increasing nutrients concentration (NPK) in rice. Also, the simultaneous foliar application of methionine and lysine led to an increase in rice grain yield through increasing 1000-grain weight and improving nitrogen uptake in rice grains.

According to the results of this experiment, the combined application of the bacteria strains (P. agglomerans strain O4 + P. putida strain P13 + P. agglomerans strain P5 + P. koreensis strain S14 + P. vancouverensis strain S19) and simultaneous foliar application of methionine and lysine can play an important role in improving growth, yield and nutrients uptake in rice grains.

Salinity stands as a significant environmental stressor that profoundly curtails the growth and yield of crop plants. This adversity also extends to the impairment of pigments and plastids, leading to diminished chlorophyll indices, rates, and grain-filling durations. To counteract the deleterious impact of such stressors on plant growth, a spectrum of strategies has been devised. Prominent among these strategies are plant growth-promoting rhizobacteria, exemplified by azospirillum, and the utilization of nanoparticles like zinc and silicon. These factors play a pivotal role in elevating yield outcomes. Zinc's pivotal involvement spans protein metabolism, photosynthetic activities, and diverse physiological traits within plants. Particularly noteworthy is its contribution to rectifying zinc deficiency, a particularly critical concern in plants cultivated in high-pH soils. Notably, recent research has illuminated the potential of applying minute quantities of micronutrients, notably zinc via foliar spraying, in bolstering plant resilience against salt stress. Likewise, silicon emerges as a supplemental micronutrient that imparts heightened resistance to environmental stresses, fostering increased resilience within biological systems. Therefore, this study aimed to evaluate the effects of application of plant growth-promoting rhizobacteria and nanoparticles (zinc and silicon) on the yield, photosynthetic pigments, and filling components of triticale grain under salt stress.

This experiment was conducted as factorial based on a randomized complete block design with three replications in greenhouse research of the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili in 2022. Factors experimental included salinity at three levels (no salinity as control, application of 60, 120 mM salinity) by NaCl, application of PGPR at two levels (no inoculation as control and seed inoculation with Azospirillium), and foliar application of nanoparticles at four levels (foliar application with water as control, foliar application of 0.8 g.L-1 nano zinc oxide, foliar application 50 mg.L-1 nano silicon, foliar application both of nano zinc oxide (0.4 g.L-1) and nano silicon (25 mg.L-1). The strains and cell densities of microorganisms used as PGPR in this experiment were 1×107 bacteria per milliliter (107 cfu.ml−1). A two-part linear model was used to quantify the grain-filling parameters. In this study, grain dry weight and number were used to calculate the average grain weight for each sample. Total duration of grain filling was determined for each treatment combination by fitting a bilinear model:    GW =where GW is the grain dry weight; a, the GW-intercept; b, the slope of grain weight indicating grain filling rate; t, the days after earring; and t0, physiological maturity. The effective grain filling period (EGFD) was calculated from the following equation:EGFD = the highest grain weight (g)/rate of grain filling (g day-1).

The results showed that application of Azospirillium and foliar application of nano zinc-silicon oxide under no salinity increased chlorophyll a (38.42%), chlorophyll b (41.76%), total chlorophyll (39.39%), carotenoids (53.99%), root weight (62.61%), grain filling rate (16.37%), grain filling period and effective grain filling period (21.28 and 29.78%) and grain yield (47.23%) in compared to no application of Azospirillium and nanoparticles under 120 mM salinity. Application of Azospirillium and foliar application nano zinc-silicon oxide under 60 mM salinity also increased chlorophyll a (31.4%), chlorophyll b (34.35%), total chlorophyll (32%), carotenoids (45.68%), root weight (57.14%), grain filling rate (15.21%), grain filling period and effective grain filling period (21.29 and 28.16%) and grain yield (35.67%) in compared to the application of Azospirillium and nanoparticles under 120 mM salinity. According to this study, application of Azospirillium and nanoparticles (zinc and silicon) can increase yield of triticale grain under salinity stress such as no salinity due to the improvement of photosynthetic pigments content and grain filling components.

In the pursuit of a resilient and progressive agricultural system, the incorporation of diverse fertilizers is deemed essential. This practice not only enhances product quality but also aids in cost reduction. However, over-reliance on a specific type of input can inadvertently lead to unintended repercussions. The unrestricted utilization of chemical fertilizers, for instance, can precipitate adverse outcomes such as imbalanced pH levels, the accumulation of heavy elements, soil structure deterioration, and environmental contamination. Conversely, organic fertilizers, while environmentally friendly, often release nutrients at a slower rate, potentially disrupting optimal plant growth. To attain a balanced and sustainable agricultural approach, the combined application of organic and chemical fertilizers is advocated. Moreover, harnessing the biological potential inherent in soil ecosystems, including beneficial microbial communities encompassing bacteria and fungi, emerges as a promising avenue in cultivating sustainable agriculture. Acknowledging the adverse impact of late-season heat stress on wheat production in Khuzestan and recognizing the significance of reducing chemical fertilizer usage while augmenting organic and biological fertilizers to foster ecological health, this experiment undertakes the exploration of the effects of a synergistic approach. Specifically, it delves into the combined utilization of nitrogen and compost fertilizers, complemented by the incorporation of plant growth-promoting rhizobacteria. This endeavor aims to shed light on how this combined strategy operates within the context of terminal heat stress, assessing its influence on the physiological attributes and yield of the wheat cultivar Chamran 2.

This experiment was carried out as split-split plots based on a randomized complete block design with three replications in the crop year of 2021-2022 in the research farm of Agricultural Sciences and Natural Resources University of Khuzestan. The experimental factors include three planting dates: December 1st, December 20th, and December 10th in the main plots; Six levels of combined use of nitrogen fertilizer with compost fertilizer include control (without nitrogen and organic), 100% nitrogen, 75% nitrogen+ 25% compost, 50% nitrogen+ 50% compost, 25% nitrogen+ 75% compost and 100% compost in sub-plots and two levels of application and non-application of plant growth promoting rhizobacteria in sub-plots. Each sub-plot was 3 meters long and 2 meters wide (with an area of 6 square meters) and included 10 crop lines at a distance of 20 cm from each other. The distance between the main and secondary plots was considered to be half a meter and the distance between the blocks was two meters. After physiological maturity, the plants were harvested and the physiological traits and grain yield were measured.

Variance analysis showed that the interaction effect of planting date, combined use of nitrogen with compost, and plant growth promoting rhizobacteria, on the traits of relative leaf water content, planting to flowering, and grain yield were significant at the 1% probability level. Also, the interaction effect of planting date and the combined use of nitrogen with compost on all traits except the length of the grain filling period and the length of sowing to physiological maturity was significant at the probability level of 1%. The mean comparison showed that the highest relative leaf water content, cell membrane thermostability, and canopy temperature depression were obtained from the treatment of 100% compost, and the highest traits of the length of sowing to flowering and length of sowing to physiological maturity were obtained in the use of 100% nitrogen. Also, the longest grain filling period, grain filling rate, and grain yield were obtained in the combined use of 50% nitrogen+ 50% compost and plant growth-promoting rhizobacteria, and the lowest value was obtained in the control of not using nitrogen and compost. In general, the delay in planting and the occurrence of terminal heat stress caused a decrease in grain yield, but on different planting dates, the combined use of 50% nitrogen+ 50% compost compared to the treatment of 100% nitrogen increased wheat grain yield.

According to the obtained results, in areas with terminal heat stress, the combined use of 50% nitrogen+ 50% compost and plant growth-promoting rhizobacteria can be considered to increase the growth and yield of wheat.