Agronomic Adaptation of Some Field Crops: A General Approach

The objective of the present study is to obtain fundamental knowledge to monitor remotely the physiological-ecological status of crops in fields (Figs 1, 2). In this paper the relationships between transpiration rate, stomatal resistance, canopy temperature, vapor pressure deficit (VPD) and photosynthetically active radiation (PAR) were investigated. A model for estimating transpiration, which was constructed using the heat balance equations, was also examined. 1. The transpiration rate had close positive correlations with the canopy temperature, VPD and PAR, although the coefficients were not significant in some cases (Table 1). 2. The stomatal diffusion resistance was closely correlated to the canopy temperature and PAR by negative coefficients and slightly correlated to the VPD. The PAR had a relatively larger negative influence on the stomatal resistance than the canopy temperature (Table 1). 3. The transpiration rate was estimated by a multi-regression equation of the canopy temperature, VPD and PAR with a coefficient of 0.84. The stomatal resistance was also estimated by a multi-regression equation of the canopy temperature and PAR with a coefficient of 0.73. These regression coefficients were relatively small, indicating that the relationship between some factors were non-linear, and that factors such as windspeed may have influenced the results (Eq. 1, 2). 4. Although those relationships described above were qualitatively ascertained, correlation coefficients obtained were not high (0.6∼0.8) enough to be used for the monitoring. 5. A model for estimating transpiration was presented, which was constructed of heat balance equations with a single leaf (Eq. 3∼7). The estimated transpiration rate calculated by substituting remotely sensed data into the model was closely correlated to the transpiration measured by means of a steady state porometer (Fig. 3, r=0.95**). As a result, the possibility was suggested to be able to estimate remotely and in real time the transpiration rate of field crops by means of the multi-sensing. An estimation model of stomatal resistance was also examined for the remote monitoring (Eq. 8∼10).

Field crops are expected to be increasingly threatened by climate change, which will negatively impact plant development, growth and yield. Phytohormones play a crucial role in regulating specific signalling pathways to induce rapid adaptive responses to environmental stresses. Exogenous phytohormone application alters hormonal balance, thereby enhancing plant adaptation to adverse conditions. While several studies have advanced our understanding of the use of phytohormones in field crops, yield responses and species-specific application strategies remain inconsistent and rarely assessed under field conditions. The application of cytokinins (CKs), abscisic acid (ABA), and gibberellic acid (GA) has been shown to maintain prolonged photosynthetic activity, stabilize plasma membrane, and reduce lipid peroxidation and ion accumulation under salinity stress in wheat. Additionally, inhibitors of ethylene synthesis and receptors can mitigate stress symptoms under drought and heat stress, which typically accelerates senescence and shortens the grain-filling period in cereal crops. In this way, exogenous application of CKs, GA, and ethylene inhibitors can delay senescence by sustaining leaf photosynthetic activity and postponing nutrient remobilization. However, these benefits may not consistently translate into improvements in grain yield and quality. This review explores the molecular mechanisms of phytohormones in abiotic stress tolerance, delineates their specific functions and evaluates experimental findings from field applications. It also summarizes the potential of phytohormone applications in field crops, emphasizing the need for species-specific investigations on application timing and dosages under open-field conditions to optimize their agronomic potential.

Quantifying the crop management influence on arable soil condition in the Inland Pampa (Argentina)

Highlights Hourly sap flow measured in co-located and identically managed maize, sorghum, and soybean closed canopies. PAR, VPD, and ETr were strongly correlated to transpiration (T) normalized by LAI. Negative response of T to high VPD (3-4 kPa) was observed for maize and sorghum. Counterclockwise hysteresis observed for diurnal T-VPD and T-PAR. MLR models were developed to estimate T using VPD and PAR. Abstract. Transpiration (T) dominates terrestrial hydrological fluxes and is strongly coupled with vegetation productivity and water use efficiency across different biomes, including agricultural systems. Studying how T in field crops responds to environmental variability has important implications to inform and predict agroecosystems’ response to a changing environment. However, comparative T rates among major field crops remain unknown in many regions where drought severity and limited freshwater availability are projected, such as the Central U.S. Plains. We address this knowledge gap by monitoring and characterizing hourly T for field-grown maize, grain sorghum, and soybean crops under the same weather, soil, and management regimes using sap flow sensors. The relationships among crop-specific T and air temperature (Tair), relative humidity (RH), wind speed (u2), vapor pressure deficit (VPD), incoming shortwave radiation (Rs), photosynthetically active radiation (PAR), net radiation (Rn), and grass- and alfalfa-reference evapotranspiration (ETo, ETr) were investigated. T normalized by leaf area index (T LAI-1) was most correlated with PAR (r=0.88), ETr (r=0.84), and VPD (r=0.81). Mean sensitivity of T LAI-1 to unit change in Tair, Rs, PAR, Rn, u2, RH, VPD, and ETr for maize and sorghum was 88% and 59% greater than that of soybean, respectively. All crops showed non-linear T LAI-1 response to increasing VPD, and a negative response of T LAI-1 to VPD was observed in the 3.0-4.0 kPa VPD range for maize and sorghum. Each crop demonstrated a counterclockwise hysteresis effect to diurnal T-VPD and T-PAR, which was 177% and 87% greater (for T-VPD) and 44% and 17% greater (for T-PAR) in maize and sorghum, respectively, than soybean. Transpiration has rarely been measured in row crops, especially in a comparative fashion, and thus, the concurrent T dynamics and their environmental controls characterized in this research are of critical importance. These data can be instrumental for quantitatively assessing change in true crop water use (transpiration) and thus crop suitability under projected environmental change. Keywords: Hysteresis, Photosynthetically active radiation, Reference evapotranspiration, Sapflow, Vapor pressure deficit.

Improving water use efficiency, nitrogen use efficiency, and radiation use efficiency in field crops under drought stress: A review

CO2 flux was measured continuously in a wheat and maize rotation system of North China Plain using the eddy covariance technique to study the characteristic of CO2 exchange and its response to key environmental factors. The results show that nighttime net ecosystem exchange (NEE) varied exponentially with soil temperature. The temperature sensitivities of the ecosystem (Q 10) were 2.94 and 2.49 in years 2002–2003 and 2003–2004, respectively. The response of gross primary productivity (GPP) to photosynthetically active radiation (PAR) in the crop field can be ex-pressed by a rectangular hyperbolic function. Average A max and α for maize were more than those for wheat. The values of α increased positively with leaf area index (LAI) of wheat. Diurnal variations of NEE were significant from March to May and from July to September, but not remarkable in other months. NEE, GPP and ecosystem respiration (R ec) showed significantly seasonal variations in the crop field. The highest mean daily CO2 uptake rate was −10.20 and −12.50 gC·m−2−d−1 in 2003 and 2004, for the maize field, respectively, and −8.19 and −9.50 gC−m−2·d−1 in 2003 and 2004 for the wheat field, respectively. The maximal CO2 uptake appeared in April or May for wheat and mid-August for maize. During the main growing seasons of winter wheat and summer maize, NEE was controlled by GPP which was chiefly influenced by PAR and LAI. R ec reached its annual maximum in July when R ec and GPP contributed to NEE equally. NEE was dominated by R ec in other months and temperature became a key factor controlling NEE. Total NEE for the wheat field was −77.6 and −152.2 gC·m−2·a−1 in years 2002–2003 and 2003–2004, respectively, and −120.1 and −165.6 gC·m−2·a−1 in 2003 and 2004 for the maize field, respectively. The cropland of North China Plain was a carbon sink, with annual −197.6 and −317.9 gC·m−2·a−1 in years 2002–2003 and 2003–2004, respectively. After considering the carbon in grains, the cropland became a carbon source, which was 340.5 and 107.5 gC·m−2·a−1 in years 2002–2003 and 2003–2004, respectively. Affected by climate and filed managements, inter-annual carbon exchange varied largely in the wheat and maize rotation system of North China Plain.

The objective of the present study was to obtain fundamental knowledge to monitor remotely the physiological and ecological status of crops in fields. In this paper the relationships between photosynthetic rate (Pn), transpiration rate (Tr), vapor pressure deficit (VPD), and other meteorological data such as photosynthetically active radiation (PAR) were investigated under field conditions. A model relating Pn and Tr was presented. The influence of chlorophyll concentration (Chl) of leaves on Pn was also examined. 1. A theoretical model to interrelate Pn and Tr was presented, which was based on the biophysical processes for gas and vapor transfer via stomata and boundary layer (Eq.1-6). Pn = a[Ca-Ci][Tr/VPD1] (6) where, a is a physical constant, Ca, Ci are ambient and substomatal CO2 concentration, respectively. The Pn is a product of the difference of those two CO2 concentrations and Tr/VPD as indicated in the eq. (6). 2. Close positive correlations between Pn and Tr/VPD were obtained for both corn and soybean as the results of experiments under field conditions. The correlation coefficients were around 0.9 and consistently higher than those coefficients between Pn and Tr in all cases. This relationship held under a wide range of environmental and crop conditions such as air temperature, PAR, VPD, soil water content, crop variety, chloropyll concentration of leaves, developmental stage, leaf position, rolling or wilting of leaves and time of measurements (Tables 1, 2). 3. Linear regression equations were obtained on the above relationships for both corn and soybean. According to those equations the difference of ambient and substomatal CO2 concentrations remains constant, because Pn is proportional to Tr/VPD. The difference of external and internal CO2 concentration was estimated as 159ppm for corn and 51ppm for soybean from the regression coefficients of those equations (Figs. 1∼2). Since the possibility of remote estimation of transpiration rate Tr had been already shown by INOUE10), the photosynthetic activity could also be estimated remotely by means of combination of remotely sensed data and meteorological data connecting above relationships. 4. As a result of the regression analysis the chlorophyll concentration (Chl) of a leaf had as large positive influence as PAR on Pn under water stress free conditions. The partial regression coefficients for Chl were around 0.7. On the other hand the effect of VPD on Pn increased negatively under water stress conditions. The partial regression coefficients were around -0.5 (Table 3).

Climate change has affected the Arctic Ocean (AO) and its marginal seas significantly. The reduction of sea ice in the Arctic region has altered the magnitude of photosynthetically available radiation (PAR) entering the water column, impacting primary productivity. Increasing cloudiness in the atmosphere and rising turbidity in the coastal waters of the Arctic region are considered as the major factors that counteract the effect of reduced sea ice on underwater PAR. Additionally, extreme solar zenith angles and sea-ice cover in the AO increase the complexity of retrieving PAR. In this study, a PAR algorithm based on radiative transfer in the atmosphere and satellite observations is implemented to evaluate the effect of these factors on PAR in the coastal AO. To improve the performance of the algorithm, a flag is defined to identify pixels containing open-water, sea-ice or cloud. The use of flag enabled selective application of algorithms to compute the input parameters for the PAR algorithm. The PAR algorithm is validated using in situ measurements from various coastal sites in the Arctic and sub-Arctic seas. The algorithm estimated daily integrated PAR above the sea surface with an uncertainty of 19% in summer. The uncertainty increased to 24% when the algorithm was applied year-round. The PAR values at the seafloor were estimated with an uncertainty of 76%, with 36% of the samples under sea ice and/or cloud cover. The robust performance of the PAR algorithm in the pan-Arctic region throughout the year will help to effectively study the temporal and spatial variability of PAR in the Arctic coastal waters. The calculated PAR data are used to quantify the changing trend in PAR at the seafloor in the coastal AO with depth < 100 m using MODIS-Aqua data from 2003 to 2020. The general trends calculated using the pixels with average PAR > 0.415 mol m−2 day−1 at the seafloor during summer indicate that the annual average of PAR entering the water column in the coastal AO between 2003 and 2020 increased by 23%. Concurrently, due to increased turbidity, the attenuation in the water column increased by 22%. The surge in incident PAR in the water column due to retreating sea ice first led to increased PAR observed at the seafloor (∼12% between 2003 and 2014). However, in the last decade, the rapid increase in light attenuation of the water column has restricted the increase in average annual PAR reaching the bottom in the coastal AO.

Soil green algae play a crucial role in terrestrial ecosystems and enhance soil health. However, research on algal diversity and ecology in crop field soils, particularly in untilled perennial tree plantations, is scarce, and the factors influencing algal contributions to soil health and fertility management are not well understood. Therefore, an extensive study was conducted on the ecology and diversity of green algae in rubber crop plantations in South India, spanning diverse agroclimatic zones, soil orders, soil series, and seasons. The primary goal was to explore how such environmental variables and soil physicochemical properties affect green algal diversity and composition in crop fields. A total of 46 green algal species were identified, indicating substantial algal biomass with about 3.176 ± 1.338g C m-2day-1 of CO2 fixation in rubber crop field soils. Many algal species showed specific ecological preferences for certain soil conditions, and significant variations in algal communities were observed across soil order, soil series, and seasons. Notable indicator species included Deasonia granata, Marochloris radiosa, and Planophila sp. Canonical correspondence analysis indicated that soil available phosphorus, pH, soil total magnesium, and total organic carbon significantly influenced algal distribution and population dynamics in rubber crop fields. Overall, these findings highlight the importance of further research on soil algae as crucial biological components of soils for environmental monitoring and assessment. These findings reaffirm their significant role in carbon sequestration within crop fields, highlighting the importance of understanding their ecological roles and agricultural applications for enhancing soil health and mitigating climate change.

More than 150 species of weeds grow in agrophytocenoses of field crops in the western part of the steppe zone of the Krasnodar Territory, of which only 38 are active to one degree or another in the cenoflora of agrophytocenoses. It has been revealed that 9 species showed the greatest activity, the indicators of their demands on the heat factor (the sum of active temperatures above +5 ° C = 1366– 3536) were closest to the indicators of heat supply in the survey area (3400–3800 °C). They clogged the crops of all examined field crops (sunflower, corn, winter wheat, oats, soybeans, alfalfa, potatoes): Ambrosia artemisiifolia L., Convolvulus arvensis L., Cirsium setosum (Willd.) Bess., Amaranthus retroflexus L., Chenopodium album L., Echinochloa crusgalli (L.) Beauv., Abutilon theophrastii Medik., Persicaria maculosa S.F. Gray, Lactuca serriola L. Less active were the species, which optimal level of requirement for heat factor (the sum of active temperatures above +5 °C = 1152–2078) was noticeably lower than in the species of the previous group: Lactuca tatarica (L.) C.A. Mey., Descurainia sophia (L.) Webb. ex Prantl, Sinapis arvensis L., Amaranthus blitoides S. Watson., Taraxacum officinale Wigg., Portulaca oleraceae L. Agrophytocenoses of all field crops included 19 more, mainly quite active and low-active species. The limits of the optimal requirements of these species to the heat factor in the zone of harmfulness (the sum of active temperatures above +5 °C = 953–2107) are significantly lower than those of the species in the first and second groups, and differ more significantly from the indicators of heat supply of the examination zone. The revealed ratio of species of different activity will be maintained provided that the weather and climatic conditions in the study area are preserved, as well as maintaining the current level of technology for cultivating field crops, and will amount as the content of a long-term regional forecast, including the above-mentioned species that will most actively have a harmful effect on the growth and development of the cultivated plants.

Weeds are one of the most damaging biotic stresses in crop production, and drought and salinity are considered the most serious abiotic stresses. These factors harmfully affect growth and development in several vegetable and field crops by causing harmful effects on physiological and biochemical characteristics such as water uptake, photosynthesis, relative water content, electrolyte leakage, and antioxidant compounds linked with oxidative stress and the accumulation of reactive oxygen species (ROS). These oxidative stress-related components affect most physiological and biochemical characteristics in plants under natural conditions and environmental stresses, especially weed infestation, salinity, and drought stress. ROS such as superoxide (O2•−), hydrogen peroxide (H2O2), peroxyl radical (ROO•), and singlet oxygen (1O2) are very important molecules produced naturally as by-products of metabolic processes in chloroplasts, mitochondria, peroxisomes, and the apoplast. Under stress conditions such as weed infestation, drought and salinity, the morphological and yield characteristics of stressed plants are negatively affected; however, superoxide (O2•−) and hydrogen peroxide (H2O2) are significantly increased. The negative impact of weeds can be mitigated with integrated controls which include herbicides, allelopathy, and crop rotation as well as the different methods for weed control. The defense system in various crops mainly depends on both enzymatic and nonenzymatic antioxidants. The enzymatic antioxidants include superoxide dismutase, glutathione reductase, and catalase; nonenzymatic antioxidants include ascorbic acid, carotenoids, α-Tocopherols, proline, glutathione, phenolics, and flavonoids. These antioxidant components can scavenge various ROS under several stresses, particularly weeds, drought and salinity. In this review, our objective is to shed light on integrated weeds management and plant tolerance to salinity and drought stresses associated with the ROS and the induction of antioxidant components to increase plant growth and yield in the vegetable and field crops.

A survey was conducted at farmers’ fields in five upazilas of Sirajganj district to find out farmers’ knowledge on crop-weed association in different field crops, crop yield losses and weeds act as alternate hosts for insect-pathogen during 2019 to 2020 cropping seasons. Primary data were collected from the respondents through a well-oriented structural questionnaire. A total of 40 weed species, belong to 35 genera under 21 families, were identified from 8 different field crops. The highest crop-weed association was found in rice (40:192) and the lowest in mustard (106:50). The maximum weed management cost was occurred in rice (38,900 Tk. ha–1). Weed caused 8 to 51% yield loss in different field crops. Our results revealed that Mutha emerged as the major noxious weed for six field crops of this district. Weeds acted as alternate hosts of various insects and pathogens. According to farmers’ opinion, weed is also used as fodder, mulch, compost, vegetables, fish feed, medicinal and ornamental purposes at their locality. Therefore, the present study provides information to extension workers and researchers about the noxious weeds and their crop-weed association, other harmful and beneficial effects of weeds, for better, sustainable, and eco-friendly weed management practices.

Biomass accumulation by crops depends on both light interception by leaves and on the efficiency with which the intercepted light is used to produce dry matter. Our aim was to identify which of these processes were affected for maize (Zea mays L., cv Volga) field crops grown under phosphorus (P) deficiency. In the preceding paper (Plenet et al., 2000), it was shown that P deficiency severely reduced leaf growth. In this paper, the effect of P deficiency on the radiation-use efficiency (RUE) was investigated. The experimental work was carried out in 1995, 1996 and 1997 on a long-term P fertilisation trial located on a sandy soil in the south-west of France. Three P fertilisation regimes have been applied since 1972: no- P (P0 treatment) and different rates of P fertiliser (P1.5: 1.5 times the grain P export and P3: 3 times the grain P export). These fertilisation regimes have led to contrasted levels of soil P supply. Only slight differences were observed between the P1.5 and P3 treatment for above-ground biomass accumulation and grain yield. Conversely the grain yield was significantly reduced in P0 (−11%). Above-ground biomass production was severely reduced, with the maximum difference between treatment (−60% in P0) occurring between 400 and 600 °C days after sowing. The lower biomass production in P0 was accounted for by the reduced amount of photosynthetically active radiation (PAR) absorbed by the canopy, which was itself the consequence of the reduced leaf area index (see Plenet et al., 2000). The calculated RUE were found to depend on the plant stage, especially during the pre-flowering period, and on the average air temperature. No effect of P deficiency was observed on the calculated RUE, even during the period when above-ground biomass accumulation was the most severely reduced. These results obtained in field crop conditions strengthen the idea that P deficiency affects plant growth, especially leaf growth, earlier and to a greater extent than photosynthesis per unit leaf area.

Reactive-nitrogen (Nr) has a wide variety of beneficial and detrimental effects on human health. The most important of the beneficial effects are increasing global and regional food supplies and increased nutritional quality of available foods. However, lack of adequate dietary intake of amino acids and proteins is a serious cause of malnutrition when food supplies are inadequate because of poverty, drought, floods, wars, and displacements of people as refugees. There is sufficient, though limited, quantitative data indicating that increased circulation of Nr in the environment is responsible for significant human health effects via other exposure pathways. Nr can lead to harmful health effects from airborne occupational exposures and population-wide indoor and outdoor air pollution exposures to nitrogen dioxide and ozone. Nr can also affect health via water pollution problems, including methemoglobinemia from contaminated ground water, eutrophication causing fish kills and algal blooms that can be toxic to humans, and via global warming. The environmental pollutants stemming from reactive nitrogen are ubiquitous, making it difficult to identify the extent to which Nr exerts a specific health effect. As all populations are susceptible, continued interdisciplinary investigations are needed to determine the extent and nature of the beneficial and harmful effects on human health of nitrogen-related pollutants and their derivatives.

SUMMARYThe crop growth model HERMES was used to model crop rotation cycles at 12 experimental sites in the Czech Republic. A wide range of crops (spring and winter barley, winter wheat, maize, potatoes, sugar beet, winter rape, oats, alfalfa and grass), cultivated between 1981 and 2009 under various soil and climatic conditions, were included. The model was able to estimate the yields of field crop rotations at a reasonable level, with an index of agreement (IA) ranging from 0·82 to 0·96 for the calibration database (the median coefficient of determination (R2) was 0·71), while IA for verification varied from 0·62 to 0·93 (median R2 was 0·78). Grass yields were also estimated at a reasonable level of accuracy. The estimates were less accurate for the above-ground biomass at harvest (the medians for IA were 0·76 and 0·72 for calibration and verification, respectively, and analogous medians of R2 were 0·50 and 0·49). The soil mineral nitrogen (N) content under the field crops was simulated with good precision, with the IA ranging from 0·49 to 0·74 for calibration and from 0·43 to 0·68 for verification. Generally, the soil mineral N was underestimated, and more accurate results were achieved at locations with intensive fertilization. Simulated yields, soil N, water and organic carbon (C) contents were compared with long-term field measurements at Němčice, located within the fertile Moravian lowland. At this station, all of the observed parameters were reproduced with a reasonable level of accuracy. In the case of the organic C content, HERMES reproduced a decrease ranging from c. 85 to 77 tonnes (t)/ha (for the 0–0·3 m soil layer) between the years 1980 and 2007. In spite of its relatively simple approach and restricted input data, HERMES was proven to be robust across various conditions, which is a precondition for its future use for both theoretical and practical purposes.