Photosynthetically Active Radiation Interception Research Articles

Nitrogen deficiency in maize fields of the Southern Pampas does not affect kernel number but reduces weight per kernel.

Nitrogen (N) requirement of maize has been increasing over the past decades, but there has been a lack of adjustment in fertilization management practices across different regions in Argentina. The higher N requirement in modern hybrids is associated with a higher post-flowering N accumulation. Additionally, soil fertility in the Argentina Pampas has consistently decreased in recent years. Whether the effects of N deficiency are expressed in the post-flowering period is still unclear at field level. The objective of this work was to quantify the yield reduction attributed to N deficiency and to identify the physiological basis of this effect at the field level for typical high-tech farms across the south-eastern Pampas of Argentina. Nineteen experiments were conducted during the 2020/2021 growing season in the south-eastern Pampas, evaluating two N managements i) Farmers' N level; ii) High N input. Results showed that the additional N input increased grain yield by an average of 6.4% (average grain yield difference of 712kgha-1). Weight per kernel was the only yield component that responded to N fertilization. Farmers' N management did not affect N accumulation or growth-related variables such as leaf area index, green leaves per plant, PAR interception, nitrogen sufficiency index until flowering, but the farmers' N level reduced these variables during the grain filling period leading to differences in aerial biomass and N accumulated at physiological maturity. Farmers' N level led to decreased post-flowering N uptake during grain filling period, which reduced the photosynthetic capacity of the canopy. These findings suggest that N management strategies and models need to be reviewed for high-tech maize systems.

Effect of Microclimate Modification on Growth and Yield of Basmati Rice under Punjab Conditions

The field experiments were conducted at the Research Farm, Department of Climate Change and Agricultural Meteorology, Punjab Agricultural University, Ludhiana during kharif 2018. Pusa Basmati variety was transplanted on 5th July (D1) and 15th July (D2) under three spacing (25 cm x12 cm, 20 cm x 15 cm and 30 cm x 10 cm). The micrometeorological data on photosynthetically active radiation (PAR) was recorded at different phenological stages. The periodic biometric observations on leaf area index were recorded. Growing degree days (GDD) were calculated at different phenological stages. The results indicate that PAR interception and leaf area index was higher under wider spacing (30 cm x 10 cm) followed by closer spacing (20 cm x 15 cm and 25 cm x 12 cm). The leaf area index was higher under wider spacing (30 cm x 10 cm) followed by closer spacing (20 cm x 15 cm and 25 cm x 12 cm). Correlation coefficients were worked out between periodic number of tillers of rice and temperature (maximum and minimum) and sunshine hours/day. In both dates of transplanting, maximum temperature showed a significant negative correlation with tiller number in most of the cases. The sunshine hours in both dates of transplanting showed a positive and significant correlation under different treatments. The first date of transplanting reported higher grain yield (30.61 q/ha) as compared to second date of transplanting (27.20 q/ha). The higher grain yield (30.57 q/ha) was recorded in basmati rice transplanted under wider spacing (30 cm x 10 cm) in comparison to closer spacing of 20 cm x 15 cm (29.25 q/ha) and 25 cm x 12 cm (26.89 q/ ha). Hence, microclimate modification through dates of transplanting and spacing is cost effective measure for increasing basmati rice yield.

Genetic regulation of self-organizing azimuthal canopy orientations and their impacts on light interception in maize.

The efficiency of solar radiation interception contributes to the photosynthetic efficiency of crop plants. Light interception is a function of canopy architecture, including plant density; leaf number, length, width, and angle; and azimuthal canopy orientation. We report on the ability of some maize (Zea mays) genotypes to alter the orientations of their leaves during development in coordination with adjacent plants. Although the upper canopies of these genotypes retain the typical alternate-distichous phyllotaxy of maize, their leaves grow parallel to those of adjacent plants. A genome-wide association study (GWAS) on this parallel canopy trait identified candidate genes, many of which are associated with shade avoidance syndrome, including phytochromeC2 . GWAS conducted on the fraction of photosynthetically active radiation (PAR) intercepted by canopies also identified multiple candidate genes, including liguleless1 (lg1), previously defined by its role in ligule development. Under high plant densities, mutants of shade avoidance syndrome and liguleless genes (lg1, lg2 and Lg3) exhibit altered canopy patterns, viz., the numbers of interrow leaves are greatly reduced as compared to those of non-mutant controls, resulting in dramatically decreased PAR interception. In at least the case of lg2, this phenotype is not a consequence of abnormal ligule development. Instead, liguleless gene functions are required for normal light responses, including azimuth canopy re-orientation.

Response of Evapotranspiration, Photosynthetic Characteristics and Yield of Soybeans to Groundwater Depth

To clarify the physiological mechanism of different groundwater depths affecting soybean evapotranspiration, photosynthetic characteristics and yield, a field experiment with four groundwater depth levels (1 m (D1), 2 m (D2), 3 m (D3) and 4 m (D4)) was conducted through the groundwater simulation system in 2021 and 2022. In this study, a quantitative analysis was conducted on the groundwater recharge and irrigation water demand and evapotranspiration (ET) of soybean fields with different treatments, and the effects of different treatments on soybean leaf area index (LAI), chlorophyll content index (SPAD), intercepted photosynthetic active radiation (IPAR), photosynthetic gas exchange parameters, dry matter accumulation (DMA) and yield were explored. The results showed the following: (1) Groundwater depth affected soybean ET and the source of ET. With the increase in groundwater depth, groundwater recharge and its contribution to ET gradually decreased, but the amount of irrigation required gradually increased, resulting in the ET as D1 > D4 > D2 > D3. (2) Soybean LAI, SPAD and IPAR were significantly affected by the different groundwater depths, of which the D1 treatment always maintained the maximum, followed by the D4 treatment, and the D3 treatment was the minimum. The photosynthetic gas exchange parameters under different treatments changed synergistically, showing significant differences in the flowering and podding stages, notably D1 > D4 > D2 > D3. Soybean DMA and yield first decreased and then increased with the increase in groundwater depth, and the average DMA and yield under the D1 treatment increased by 27.71%, 46.80% and 22.82% and 20.29%, 29.91% and 12.83% in the two years, respectively, compared to the D2, D3 and D4 treatments. (3) The structural equation model demonstrated that the groundwater depth indirectly affected the growth of soybean leaf area by affecting groundwater recharge, which in turn regulated soybean ET and photosynthetic capacity and ultimately affected DMA and yield. The above results showed that in the case of shallow groundwater depth (D1), the largest groundwater recharge promoted the growth of soybean leaf area and chlorophyll synthesis and increased the absorption and utilization of solar radiation. And it improved the leaf stomata conditions, accelerated the gas exchange between the plant and atmosphere, enhanced the photosynthetic production capacity and ET and achieved maximum DMA and yield. Soybean leaf growth and photosynthesis diminish with the increase in groundwater depth. In the case of deep groundwater depth (D4), the maximum irrigation improved the growth and photosynthetic performance of soybean leaves, which was favorable to ET, and ultimately led to increases in DMA and yield.

Importance of PAR interception and radiation use efficiency on growth and yield of Potatoes under different microclimates in the upper Brahmaputra valley zone of Assam

A field experiment was conducted at Assam Agricultural University, Jorhat, Assam during rabi 2018-19 for assessing the PAR interception and radiation use efficiency in potato variety Kufri Jyoti under different microclimates, which was planted in split plot design with 4 dates of plantings and three mulching treatments with water hyacinth, black polythene and without mulching. The incident, reflected and transmitted PAR were measured periodically over the crop with line quantum sensor and daily incident radiation were calculated from incident PAR and bright sunshine hours. The interception of PAR (iPAR) varied considerably among different treatments, while highest iPAR was recorded under first date of planting and mulching treatment with water hyacinth. The leaf area index (LAI) and biomass production was highest in crop planted in first date planting and grown under water hyacinth mulch. The RUE for tuber yield was highest under water hyacinth (2.35 g MJ-1) followed by black polythene (2.03 g MJ-1) and non-mulched (1.67 g MJ-1) condition, while among planting dates it was highest in case of first date of planting. The  LAI, biomass production and yield of potato were found to be significantly correlated with iPAR and RUE. The predictive models were developed by using stepwise regression method to predict tuber yield from iPAR and REU, which have R2 value of 0.96 and 0.99, respectively. 
  

Monthly intercepted photosynthetically active radiation estimation based on the Beer-Lambert’s law across the cereal crops of Castilla y León (Spain)

Agriculture is by far the most important economic activity in the Spanish autonomous region of Castilla y León. Numerous factors influence crop development but one of the most related variables to the photosynthetic process is Photosynthetically Active Radiation (PAR). Estimating Intercepted Photosynthetically Active Radiation (IPAR) in different crops through the Beer-Lambert law could be a relevant factor in crop season planning by enabling photosynthesis monitoring. The Beer-Lambert Law is applied in this study to the data for almost 2 million hectares of wheat, barley, and maize cultivated in Castilla y León in 2021. The fourteen-year data set of Global Horizontal Irradiance (GHI) used to calculate the monthly PAR data in the region was collected at 93 meteorological stations (46 in Castilla y León and 47 in neighboring Spanish and Portuguese regions). Two previously published global calibrated models were employed to calculate the PAR, with a relative Root Mean Square Error (rRMSE) below 6%, for the measured daily mean values of PAR in Burgos. Processing the various NASA Terra and Aqua satellite images yielded the monthly Leaf Area Index (LAI) and the literature review provided the light extinction coefficient (k). The Geographic Information System (GIS) facilitated visualization of IPAR estimates for the three cereal crops in all months of its growing season. Wheat and barley reach their IPAR peaks in June and July, while maize peaks in July and August. In addition, the fraction of Intercepted Photosynthetically Active Radiation (fIPAR) was calculated in different provinces to assess PAR interception for each cereal at different growing stages. In June, almost 50% of the wheat area in Burgos, Palencia and Soria displayed fIPAR values exceeding 45% while in the case of barley only the province of Burgos reached these percentages of area and.fIPAR.

Delayed Leaf Senescence Improves Radiation Use Efficiency and Explains Yield Advantage of Large Panicle-Type Hybrid Rice

Super hybrid rice with predominantly large panicle types has achieved remarkable success in enhancing crop yield. However, when compared with multi-panicle-type varieties, the yield stability of large panicle-type varieties remains a challenge, and limited information is available on the comparative advantages of multi-panicle types. Consequently, a two-year experiment was conducted to evaluate the grain yield, biomass production, leaf area index (LAI), and radiation use efficiency (RUE) of large panicle-type hybrid rice (Y-liangyou 900, YLY900) and multi-panicle-type hybrid rice (C-liangyouhuazhan, CLYHZ) under three nitrogen (N) treatments (0, 180, 270 kg N ha−1). The effects of increased N fertilization were more pronounced in the large panicle-type varieties. YLY900 outperformed CLYHZ in terms of average yield (6% higher), and its yield advantage was attributed to higher spikelets per panicle (28%). Due to YLY900’s RUE being 9% higher than CLYHZ, it results in a 12% greater accumulation of dry matter than CLYHZ. Furthermore, YLY900 exhibited significant improvements of 16%, 4%, and 14% in specific leaf weight, effective leaf area ratio, and LAI at 20 days after the heading stage (20DAH), respectively, compared with CLYHZ. YLY900 also demonstrated a stronger correlation between rice yield and intercepted photosynthetically active radiation (IPAR) compared with CLYHZ, with R2 values of 0.80 and 0.66, respectively. These findings highlight the superior performance of YLY900, resulting from higher light interception percentage (IP) and IPAR values, which consequently led to enhanced RUE and grain yield. Our research reveals that delayed leaf senescence by increasing LAI at the post-heading stage for large panicle-type hybrid rice, thereby contributing to greater RUE, led to higher biomass production and grain yield.

Assessing on yield difference of double-cropping rice in South China driven by radiation use efficiency

Double-cropping rice in South China continued to break through the total yield record, but the yield potential of single-cropping rice wasn’t realized. Radiation use efficiency (RUE) has been singled out as an important determinant of grain yield in cereal species. However, there is no information on whether this yield gaps involved differences to RUE in double-cropping rice. Field experiments were performed over two years to evaluate the effects of intercepted radiation (IP) and RUE, on the above-ground biomass production, crop growth rate (CGR), and harvest index (HI), in four representative rice varieties, i.e., Xiangyaxiangzhan (XYXZ), Meixiangzhan-2 (MXZ2), Nanjingxiangzhan (NJXZ), and Ruanhuayoujinsi (RHYJS) during the early seasons and late seasons of rice cultivation in South China. The results revealed that grain yield of early season was 8.2% higher than late season. The yield advantage in early season was primarily owing to higher spikelet per panicle and above-ground biomass resulting from a higher RUE. The spikelet per panicle in the early season were 6.5, 8.3, 6.9, and 8.5% higher in XYXZ, MXZ2, NJXZ, and RHYJS than late season. The higher grain yield in early season was more closely related to RUE in middle tillering stage (R2=0.34), panicle initiation (R2=0.16), maturation stage (R2=0.28), and intercepted photosynthetically active radiation (IPAR) in maturation stage (R2=0.28), while the grain yield in late season depended higher IPAR in middle tillering stage (R2=0.31) and IPAR in panicle initiation (R2=0.23). Conclusively, the results of this research show that higher RUE contribute to yield progress of early season rice, while the yield improvement of late season rice is attributed to higher radiation during early reproductive stage. To rationally allocate the RUE of the double-cropping rice with high RUE varieties or the adjustment of sowing period deserve the further studied.

Physiological contributors to yield in advanced cotton breeding lines

AbstractCotton (Gossypium hirsutum L.) yield can be expressed as the product of intercepted photosynthetically active radiation (IPAR), radiation use efficiency (RUE), and harvest index (HI). Studies comparing genetic diversity in functional yield drivers for the progeny of elite breeding lines are limited or non‐existent. A field study was conducted during the 2020 and 2021 growing seasons to characterize crop development and to evaluate yield and underlying yield drivers in 16 advanced breeding lines (F7 generation). Significant breeding line differences existed for lint yield, cutout date, reproductive, vegetative, and total biomass, RUE, and HI but not for IPAR. The lint yield for the lowest yielding lines was 24% lower than the highest yielding line with a lint yield of 1706 kg ha−1. Differences in RUE were not associated with single‐leaf photosynthetic rates. HI positively contributed to lint yield gain for most lines evaluated, whereas RUE was negatively correlated with lint yield for the majority of breeding lines evaluated. However, in the two highest‐yielding lines, two different strategies of yield maximization were identified. One line exhibited the earliest cutout date, reduced biomass production, low RUE, and the highest HI values, whereas the other line had the latest cutout date and produced the highest total biomass, highest RUE, and a low to intermediate HI. Breeding lines used in the current study achieved high yields by differentially manipulating underlying physiological components such as RUE, biomass accumulation, or dry matter allocation to fiber. Our work provides future direction for efforts aimed at maximizing yield through the selection for functional yield drivers.

A novel simulation model to predict photosynthetic active radiation interception in micro-irrigated citrus production orchards based on tree spacing, canopy geometry, and row orientation

Diurnal and seasonal patterns of photosynthetically active radiation (PAR) intercepted by tree canopies in production orchards have an important role for eco-physiological processes that determine tree water use and productivity. Under well-watered conditions, PAR intercepted by trees is a reliable predictor of crop consumptive water use, which is regulated by tree spacing, tree row orientation, and by the tree canopy dimensions and geometry. Despite its advantages, only rare attempts have been made by the scientific and fruit production communities to develop canopy PAR interception simulators that rely on analytical principles to inform irrigation planning and management decisions. In this article, a novel model is presented that simulates PAR interception by citrus trees based on the canopy geometry and its shading patterns. The article also illustrates preliminary field testing and validation of the model with data collected in commercial citrus production orchards located in the San Joaquin Valley of California. The testing and validation could enable citrus growers and orchard managers to predict the net radiation for mature, micro-irrigated Navel orange and Page mandarin orchards grown with north–south and east–west tree row orientations and different tree densities. Results from the simulations and field validation showed that the canopy PAR light interception contributed 58.8 (± 0.02) and 71.1 (± 1.60) percent to the overall net radiation for the Navel orange orchards during the periods around summer solstice and autumnal equinox, respectively, whereas for the Page mandarin orchards, PAR light interception contributed 63.0 (±5.60) and 85.7 (±18.87) percent to the overall net radiation during the same time periods. Good correlations were found between daily values of PAR and net radiation for these citrus production orchards grown with the two alternative row orientations, which suggest that the proposed model could be used to inform irrigation planning and management decisions for different site-specific citrus orchard features and growing conditions.

Assessment of PAR Interception and Radiation Use Efficiency on Tomato Growth and Yield in the Upper Brahmaputra Valley Zone of Assam, India

A field experiment was conducted in Jorhat, Assam during the rabi season of 2019-20 to examine the effects of PAR interception, radiation use efficiency, and modified microclimates on tomato growth and yield. The variety Arka Rakshak was grown in split plot design with 4 dates of planting (P1: 25th October, P2: 14th November, P3: 3rd December, and P4: 8th January) in main plots and three types of mulching (M0: no mulch, M1: rice straw mulch, and M2: black polythene mulch) in sub-plots. Measurements of incident PAR (IPAR), reflected PAR (RPAR), transmitted PAR (TPAR) were taken at 10 days regular intervals. The results showed that IPAR ranged from 531 to 1431 μ mol s-1 m-2, with an average of 1140.4 μ mol s-1 m-2. RPAR varied between 41 and 285 μ mol m-2 s-1 under different microclimates. The tomato yield ranged from 76.6 to 392.6 q ha-1, with an average of 234.9 q ha-1. Planting on November 14th (P2) provided the most favorable microclimate conditions, while black polythene mulch (M2) was found to be the most suitable for crop growth, yield, and radiation use efficiency due to increased soil temperature. The study indicated that selecting the right planting date and implementing black polythene mulch can enhance tomato growth, yield, and radiation use efficiency in Upper Brahmaputra Valley Zone of Assam (Jorhat) agro-climatic condition.

Optimizing Grain Yield and Radiation Use Efficiency through Synergistic Applications of Nitrogen and Potassium Fertilizers in Super Hybrid Rice.

The remarkable yield performance of super hybrid rice has played a crucial role in ensuring global food security. However, there is a scarcity of studies investigating the contribution of radiation use efficiency (RUE) to hybrid rice yields under different nitrogen and potassium treatments. In this three-year field experiment, we aimed to evaluate the impact of two hybrid rice varieties (Y-liangyou 900: YLY900 and Quanyouhuazhan: QYHZ) under varying nitrogen regimes (N90: 90 kg N ha-1, N120: 120 kg N ha-1, N180: 180 kg N ha-1) and potassium regimes (K120: 120 kg K2O ha-1, K160: 160 kg K2O ha-1, K210: 210 kg K2O ha-1) on grain yield and its physiological determinants, including RUE, intercepted photosynthetically active radiation (IPAR), aboveground biomass production, and harvest index (HI). Our results revealed that both rice varieties exhibited significantly higher yields when coupled with nitrogen and potassium fertilization. Compared to the N90 × K120 treatment, the N120 × K160 and N180 × K210 combinations resulted in substantial increases in grain yield (12.0% and 21.1%, respectively) and RUE (11.9% and 21.4%, respectively). The YLY900 variety showed notable yield improvement due to enhanced aboveground biomass production resulting from increased IPAR and RUE. In contrast, the QYHZ variety's aboveground biomass accumulation was primarily influenced by RUE rather than IPAR, resulting in higher RUE and grain yields of 9.2% and 5.3%, respectively, compared to YLY900. Importantly, fertilization led to significant increases in yield, biomass, and RUE, while HI remained relatively constant. Both varieties demonstrated a positive relationship between grain yield and IPAR and RUE. Multiple regression analysis indicated that increasing RUE was the primary driver of yield improvement in hybrid rice varieties. By promoting sustainable agriculture and enhancing fertilizer management, elevating nitrogen and potassium levels from a low base would synergistically enhance rice yield and RUE, emphasizing the critical importance of RUE in hybrid rice productivity compared to HI.

Quantifying physiological contributions to nitrogen-induced yield variation in field-grown cotton

The effect of nitrogen (N) application rate on lint yield and yield components have been studied extensively in cotton. However, reports quantifying contributions to N-induced yield loss and the response of intra-boll yield components to N deficiency are far less common. The objectives of this study were to 1) determine the effect of N application rate on lint yield biomass and fiber quality in cotton, 2) assess the contributions of intercepted photosynthetically active radiation (IPAR), radiation use efficiency (RUE), and harvest index (HI) to N-induced yield loss in cotton, and 3) characterize the effect of N application rate on yield component responses in cotton. An experiment was conducted at a field site near Tifton, Georgia, USA during the 2021 and 2022 growing seasons. The experiment was arranged as a randomized complete block design with five replications and five nitrogen application rates (0, 44, 89, 134, and 179 kg N ha−1). The studied parameters were lint yield, IPAR, RUE, HI, fiber quality, yield components, and yield loss contributions. Lint yield was significantly affected by N application rate, with yields ranging from 1452 to 1848 kg ha−1. Similarly, total IPAR was 23% lower for the 0 kg N ha−1 treatment than the 134 kg N ha−1 treatment, and IPAR contributed significantly to yield loss, with a 427 kg ha−1 loss attributable to IPAR under N deficiency. RUE was 37% higher for the 179 kg N ha−1 treatment than the 0 kg N ha−1 treatment and contributed positively to yield in the highest N rates (179 kg N ha−1). However, yield improvements due to RUE were mitigated by low HI values in the highest N application rate. Boll density was the most strongly and positively associated yield component parameter with N-induced variability in lint yield, whereas lint percent and lint production per seed were negatively associated with lint yield. Among the three physiological yield-driving parameters, light interception by the canopy was the primary contributor to N-induced yield loss. Boll density was the primary yield component governing N-induced variation in lint yield. Increased N application rate promotes greater dry matter partitioning to seeds than fiber, resulting in more seeds per boll and lower lint percent, lint weight per seed, and individual fiber weight. The results contained here identify the most important functional traits for determining lint yield response to N application rate.

High-low seedbed cultivation drives the efficient utilization of key production resources and the improvement of wheat productivity in the North China Plain

High-low seedbed cultivation (HLSC) is a key technique now used by smallholder and large farmers to increase the land utilization rate of wheat production in the North China Plain (NCP). However, little information is available on its superiority in crop productivity, resource utilization efficiency, and net return in comparison with flat cultivation (FC). A field experiment was conducted in the NCP in the 2020–2021 and 2021–2022 wheat seasons to determine whether HLSC would increase crop productivity, evapotranspiration (ET), intercepted photosynthetically active radiation (IPAR), crop nitrogen uptake and resource use efficiency. Two treatments were established, i.e., FC and HLSC, respectively. The results showed that HLSC significantly increased tiller development, leaf area index (LAI), and aboveground biomass compared with FC. Although HLSC did not increase ET relative to FC (P > 0.05), it increased IPAR by 5.5–6.6 % and grain nitrogen uptake by 12.1–12.6 % (P < 0.05). Pearson correlation analysis indicated that grain yield and biomass yield were regulated by the resource capture of wheat. Therefore, HLSC significantly increased grain yield by 14.5–18.3 % and net return by 45.4–59.3 % and enhanced the efficient use of resources by 13.2–15.6 % in water, 8.5–11.1 % in radiation, and 14.5–18.3 % in nitrogen compared with FC. HLSC is a promising planting system for improving crop productivity and resource use efficiency.

Significance of Plant Canopy Maintenance in Crop Yield

The yield of any crop depends on the capacity of a plant canopy to intercept and efficiently use the sunlight, which is dependent on canopy architecture of a plant viz., leaf size, shape and angle, number of leaves and branches, and a crop geometry viz., row orientation, row spacing, plant geometry, plant density, etc. The amount and distribution of leaf area in a crop canopy determine the way, by which, the photosynthetic active radiation is intercepted and consequently it influences the canopy photosynthesis and yield. The balance between the source and sink significantly contributes towards the higher accumulation of photosybthates  Cropping geometry of a plant/crop affects the radiation use efficiency, intercepted photosynthetic active radiation (IPAR) and thereby the biological and economical yield of a crop. Optimum plant population stand and its density and a planting pattern with adequate spatial arrangement are important cultural factors that increase radiation interception and yield production.

Balancing water and radiation productivity suggests a clue for improving yields in wheat under combined water deficit and terminal heat stress.

Sustaining crop yield under abiotic stresses with optimized resource use is a prerequisite for sustainable agriculture, especially in arid and semi-arid areas. Water and heat stress are major abiotic stresses impacting crop growth and yield by influencing complex physiological and biochemical processes during the life cycle of crops. In a 2-year (2015-2017) research, spring wheat cv. HD-2967 was grown under deficit irrigation and delayed sowing conditions to impose water and terminal heat stresses, respectively. The data were analyzed for seasonal crop water use, radiation interception, water productivity (WP), and radiation productivity (RP) under combined water deficit and terminal heat stresses. Seasonal crop water use was significantly affected by stresses in the order of water + terminal heat > water > terminal heat. Water stress showed minimal effect on the light extinction coefficient and consequently on seasonal intercepted photosynthetically active radiation (IPAR). However, seasonal IPAR was primarily affected by combined water + terminal heat and terminal heat stress alone. The slope of crop water use and IPAR, i.e., canopy conductance, an indicator of canopy stomatal conductance, was more influenced by water stress than by terminal heat stress. Results showed that linear proportionality between WP and RP is no longer valid under stress conditions, as it follows a curvilinear relation. This is further supported by the fact that independent productivity (either water or radiation) lacked the ability to explain variability in the final economic yield or biomass of wheat. However, the ratio of RP to WP explained the variability in wheat yield/biomass under individual or combined stresses. This suggests a clue for improving higher wheat yield under stress by managing WP and RP. The highest biomass or yield is realized when the ratio of RP to WP approaches unity. Screening of genotypes for traits leading to a higher ratio of RP to WP provides an opportunity for improving wheat productivity under stressed environments.

Importance of solar radiation and the need for improved respect to Sun by Agrometeorologists

Solar radiation refers to energy produced by the Sun, some of which reaches the Earth. This is the primary energy source for most processes in the atmosphere, hydrosphere, and biosphere. Solar radiation is of crucial importance inproviding the energy source for photosynthesis.  During 1973 to 1977, when I did my Ph.D. in Agroclimatology in the Iowa State University, USA, I conducted the field experiments during 1975 and 1976 on soil-plant-water relations, growth and nutrient uptake patterns of field grown soybeans under water stress at the Western Iowa Experimental Farm, Castana.  During these experiments, the solar radiation was measured with a pyranometer sensor mounted on an anodized aluminimum base. Daily solar radiation values were obtained from an LI-500 integrator attached to the pyranometer sensor.  The attenuation of photosynthetically active radiation (PAR) and net radiation (NRAD) in the soybean canopy was determined during the growing season by using vertical profiles of radiation and leaf-area-index values.  Once I received my Ph.D., I worked at the Headquarters of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Hyderabad from 1977 to 1983 and at the ICRISAT Sahelian Center, Niamey, Niger from 1984 to 1996.  In several field experiments in ICRISAT, the hourly values of net radiation were obtained through net radiometers mounted above the crop canopies.  The growth and interception of PAR in a maize/pigeonpea intercrop and sole maize and sole pigeonpea crops grown in large plots were compared.  The productivity of maize, sorghum, pigeonpea and a maize/pigeonpea intercrop in the operational research watersheds was measured in relation to the interception of PAR.  In another study, it was shown that different shading ability of the crop canopies was one of the factors which determined the crop/weed competition balance and thus contributed to differential crop productivity observed in different cropping systems.  Afterwards, when I worked at the World Meteorological Organization from 1996 to 2016 as the Chief of the Agricultural Meteorology Department, as the Director of the Climate Prediction and Adaptation Branch and as the Acting Secretary of the Intergovernmental Panel on Climate Change, a lot of work was done on Solar Radiation.  Given all the above work on Solar Radiation, I emphasized the need for improved respect to Sun Bhagawan by Agrometeorologists at the end of this article.

Sowing density rather than row spacing influences chia radiation use and yield

AbstractChia (Salvia hispanica L.) production worldwide has been encouraged due to its high essential fatty acid content that is effective for reducing cardiovascular affections. However, few studies have assessed the sowing density and row spacing to maximize chia grain yield (GY) and found controversial results. None of them reported effects on radiation interception and use efficiency that could help to clarify the controversial results. The objective of this study was to determine the effects of sowing density and row spacing on radiation interception and radiation use efficiency (RUE) of chia and their effects on chia growth and yield. Two field trials were conducted in Salta, Argentina, during 2017 and 2018, combining two factors: sowing density (5, 9, 13, 17, and 21 plants m−2) and row spacing (0.26 and 0.52 m). Photosynthetically active radiation (PAR) interception (PARi), RUE, biomass and GY components were measured. There was a clear effect of sowing density on the main growth and yield attributes, whereas there were no effects of row spacing. Sowing density had a greater impact on PARi than row spacing. Increasing sowing density increased PARi and RUE through earlier time of maximum PARi, accumulating more PAR producing more biomass and GY. Grain yield, which increased by 73 kg ha−1 per unit increase in plant density, was closely associated with biomass, grain number, and verticillaster number (VN), and negatively associated with 1,000‐grain weight (TGW). Summarizing sowing density rather than row spacing had a greater impact on growth and yield attributes of chia.

Effect of AVG (Retain®) on yield and twin seeds incidence of almond trees, and orchard profit under different conditions of fruit set and PAR interception

ISHS XIV International Symposium on Plant Bioregulators in Fruit Production Effect of AVG (Retain®) on yield and twin seeds incidence of almond trees, and orchard profit under different conditions of fruit set and PAR interception

Effects of plastic film mulching on the spatiotemporal distribution of soil water, temperature, and photosynthetic active radiation in a cotton field.

Plastic film mulching (PFM) affects the spatiotemporal distribution of soil moisture and temperature, which in turn affects cotton growth and the spatiotemporal distribution of canopy photosynthetically active radiation (PAR). Due to the spatial heterogeneity of soil moisture, temperature and limited monitoring methods, the issues such as relatively few sampling points and long sampling intervals in most existing studies prevent the accurate quantification of spatiotemporal changes in moisture and temperature along soil profile. To investigate the effects of PFM on spatiotemporal changes in soil moisture, temperature, and canopy PAR in cotton fields, two field trials of plastic film-mulched (M) and nonmulched (NM) cultivations were performed in 2018 and 2019. The grid method was used for the soil information continuous monitoring and multiple-time fixed-site canopy PAR monitoring during the duration of cotton growth. Two-year field trial data showed that, M cultivation increased soil moisture by approximately 13.6%–25% and increased temperature by 2–4 °C in the 0–50 cm soil layer before the first irrigation (June 20) and by 1–2 °C in the 70–110 cm soil layer, compared with NM cultivation. In addition, the temperature difference between the two treatments gradually decreased with the increase in irrigation and air temperature. The M treatment reached the peak PAR interception rate 10 days earlier than the NM treatment. In 2018 and 2019, the PAR peak value under the M treatment was 4.62% and 1.8% higher than that under the NM treatment, respectively, but the PAR interception rate was decreased rapidly in the late growth stage. Overall, PFM had an effect on soil moisture retention during the whole growth period and greatly increased the soil temperature before budding stage, thus promoted the early growth of cotton. Considering this, we suggest that the irrigation quota and frequency could be appropriately decreased in the case of plastic film mulching cultivation. For nonmulching cultivation, the irrigation quota and frequency should be increased, and it is necessary to take measures to improve the soil temperature before middle July.