Photosynthetically Active Radiation Interception Research Articles

Canopy light distribution effects on light use efficiency in wheat and its mechanism

Optimizing canopy light distribution (CLD) has manifested improved light utility and yield without modifying other inputs. Nonetheless, molecular mechanisms working at cellular and organelle level remain to be elucidated. The current study aimed to assess the effect of CLD on photosynthetic performance and yield of wheat, and to investigate into the molecular mechanism underlying the photosynthetically active radiation (PAR)–use efficiency (PUE) at optimized CLD. Wheat was planted in two rows having different spacing [R1 (15 cm) and R2 (25 cm)] to simulate different CLD. Flag and penultimate leaves were subjected to chloroplast proteomics analysis. An increase in row spacing positively affects CLD. A decrease (16.64%) of PAR interception in the upper layer, an increase (19.76%) in the middle layer, improved PUE (12.08%), and increased yield (9.38%) were recorded. The abundance of proteins associated with photosynthetic electron transport, redox state, and carbon-nitrogen assimilation was differentially altered by CLD optimization. In the penultimate leaves, R2 reduced the abundance of photosystem II (PSII) light-harvesting proteins, PSII-subunits, and increased the photosystem I (PSI) light-harvesting proteins, NAD(P)H quinone oxidoreductase (NQO) and enzymes involved in carbon assimilation compared to R1. Additionally, leaf stomatal conductance increased. Altogether, these findings demonstrated that the regulation of chloroplast proteome is intimately linked to light utilization, which provide basis for genetic manipulation of crop species for better adaptation and improvement of cultivation strategies.

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.

Radiation use efficiency and biomass production of maize under optimal growth conditions in Northeast China.

Accurate crop growth and radiation use efficiency (RUE) measurements under optimal growth conditions are required to predict grain yield near the genetic growth potential and estimate climate change effects on crop production. Research was conducted to quantify RUE of maize during the whole growth period, vegetative period (VP, phenological development stage DVS < 1.0), and reproductive period (RP, DVS ≥ 1.0) under the optimal growth condition in Northeast China. Maize was grown in three population density treatments (9.0, 7.5, and 6.0 plants m-2, referred to HD, MD, and LD respectively) over three growing seasons (2017-2019). The maximum Leaf Area Index (LAI) was observed after the anthesis period (DVS = 1.2), ranged from to 4.9 to 6.9, and then gradually decreases. Photosynthetically active radiation (PAR) intercepted by the canopy of maize was approximate 10% during the early stage of the vegetative period (DVS < 0.3). Then greatest differences occurred during the late vegetative period (DVS = 0.3 to 0.8). When DVS > 1.0, there is no significant difference between the three population density conditions. Estimates of RUE were obtained based on the intercepted PAR (IPAR) and absorbed PAR (APAR). RUE value was 3.97 g MJ-1 APAR or 3.73 g MJ-1 IPAR in the whole growth period, and did not vary among density treatments. Moreover, maximum RUE occurred during VP (4.11 g MJ-1 APAR) and declined during RP (3.95 g MJ-1 APAR). Therefore, we recommend that maize models that rely on RUE for aboveground biomass accumulation should be using a value of 3.97 g MJ-1 APAR for predicting optimum maize grain yield in Northeast China, especially for the potential yield.

Effect of malt barley varieties and nitrogen levels on crop phenology, PAR interception, GDD, RUE and thermal use efficiency under saline water irrigation

Barley is one of the most salt tolerant crops and can be adopted in a condition where the irrigation quality of the water is saline in nature. Due to uncertainty of rainfall and scarcity of water, farmers of Haryana often irrigate the crops with poor quality water and this situation is likely to become more alarming with the depleting water resources. Therefore, an experiment was conducted at CCS Haryana Agricultural University, Hisar during rabi seasons of 2017-18 and 2018-19 to evaluate the effect of different malt barley varieties and nitrogen levels on crop phenology, PAR interception, GDD, radiation use efficiency and thermal use efficiency. The experiment was laid out in split plot design by keeping four varieties (BH 902, BH 946, BH 885 and DWRB 101) in main plots and four nitrogen levels (0, 30, 60 and 90 kg/ha) in sub plots with four replications. Variety BH 902 recorded significantly higher grain yield and took maximum number of days for flag leaf emergence, spike initiation and physiological maturity than variety BH 946, BH 885 and DWRB 101, respectively. Highest GDD, radiation use efficiency and thermal use efficiency was recorded by variety BH 946 which was statistical at par with DWRB 101 and significantly higher than BH 902 and BH 885. Application of 90 kg N/ha took maximum number of days for flag leaf emergence, spike initiation and physiological maturity as well as recorded higher GDD, radiation use efficiency and thermal use efficiency as compared to 0, 30 and 60 kg N/ha.

Plant Population and Row Spacing Affects Growth and Yield of Rainfed Maize in Semi-arid Environments.

Increased tolerance to competition for soil resources of modern maize (Zea mays L.) hybrids increases soil resource use efficiency and yield. Yet little information is available on the relationship between maize population density and yield under no-tillage in semi-arid environments. A 2-year field trial was conducted in South Africa during the 2017/2018 (Season 1) and 2018/2019 (Season 2) production seasons to evaluate growth and water use productivity of rainfed maize established at seven diverse plant population (20,000–60,000 plants ha−1) and row spacing (0.52 and 0.76 m) configurations. In Season 1, light interception was 6.8% greater at 0.76 m row spacing compared to 0.52 m row spacing (p < 0.05). In Season 2, despite dry and hot growing conditions, a well-developed leaf canopy cover was present at 0.52 m row spacing indicating a 10.4% greater intercepted photosynthetically active radiation (IPAR) compared to 0.76 m row spacing. In Season 1, with more uniform rainfall distribution, no biomass or yield benefits were found with increased plant population, except at 50,000 plants ha−1 at 0.76 m row spacing. In Season 2, plant populations at 0.76 m row spacing out-yielded any given plant population at 0.52 m row spacing. The optimal plant population and row spacing will ultimately be a compromise between obtaining high maize grain yield and minimizing the potential for crop failure in semi-arid environments.

Radiation Use Efficiency and Agronomic Performance of Biomass Sorghum under Different Sowing Dates

Accurate estimation of radiation use efficiency (RUE) at variable timed sowing dates will enhance the prediction of plant dry matter accumulation. The objectives of this study were to (1) determine the impact of three sowing dates on the productivity, performance, and economic feasibility of three biomass sorghum hybrids and (2) evaluate the variability of RUE in the production of biomass sorghum under the effects of variable timed sowing dates. Over a two-year experiment, biomass sorghum hybrids were grown and monitored at different sowing seasons under optimal growth conditions. Average dry biomass (DB) productivity at harvest ranged from 22.71 to 32.77 Mg ha−1. Higher leaf area index (LAI) values (&gt;4.0) represented an intercept of over 95% of incident photosynthetically active radiation (PAR). RUE obtained from the slope of the linear relationship between DB produced and accumulated intercepted photosynthetically active radiation (IPAR) ranged from 2.92 to 4.157 g MJ−1 across growing seasons. Higher RUE values were observed for the energy hybrids in the early and mid-season. They converted IPAR efficiently into DB. Lastly, the economic feasibility of each sorghum hybrid and sowing date was evaluated in terms of their expected net returns. Economic results suggest that the sorghum hybrids considered could be a viable source of biomass season long, with net returns ranging from USD 560.55 ha−1 to USD 1255.06 ha−1.

Seed Priming and Foliar Application of Nutrients Influence the Productivity of Relay Grass Pea (Lathyrus sativus L.) through Accelerating the Photosynthetically Active Radiation (PAR) Use Efficiency

The efficiency of a crop to intercept and utilize solar radiation for photosynthates production serves as one of the deciding factors of the productive potential of the crop stand. Interception and use efficiency of photosynthetically active radiation (PAR) were estimated in relay grass pea under different nutrient management schedules in consecutive two crop seasons of 2017–2018 and 2018–2019. Treatments were two levels of seed priming (i.e., 1. S1: Without seed priming and 2. S2: Seed priming with ammonium molybdate at 0.5 g kg−1 seed) and five levels of foliar-applied nutritions with various combinations of 2% Urea and 0.5% NPK (19:19:19) shuffling their times of application, replicated thrice laying out in a factorial randomized block design. Seed priming along with twice sprays of NPK (19:19:19) at pre-flowering followed by a second one after 15 days recorded maximum leaf area index (LAI) and total chlorophyll content augmenting greater interception and use efficiency of PAR with highest biomass accumulation, crop growth rate (CGR) and leaf nutrient contents leading to a significant increase in seed yield over control (1696.70 and 1182.00 kg ha−1, respectively) in a pooled analysis. LAI and total chlorophyll content established linear relationships with PAR interception explaining about 94 and 88% variations in intercepted PAR at 90 DAS. Intercepted PAR during different phenophases was positively correlated to dry matter accumulation and net photosynthetic rate with polynomial relationships. Seed yield of grass pea varied about 95 and 96% respectively during 2017–2018 and 2018–2019 with the variations in PAR interception at the pod developmental stage.

Deficit irrigation maintains maize yield through improved soil water extraction and stable canopy radiation interception

AbstractDeficit irrigation (DI) is an effective way to save irrigation water while maintaining sustainable yield in irrigated crops. However, limited information is available related to canopy structure and solar radiation use under DI condition. In this study, our objective was to assess maize hybrids for leaf development, photosynthetically active radiation (PAR) interception and water use under DI condition. Field experiments were conducted in 2016 and 2017 in four maize hybrids at well‐watered (I100, referring to 100% evapotranspiration [ET] requirement) and DI (I75, referring to 75% ET requirement) water regimes. Compared to I100, I75 did not reduce maize biomass and grain yield. Although DI reduced the leaf appearance rates (1.5% in 2016 and 7.6% in 2017) and resulted in greater variations in leaf area index (LAI) among hybrids, the amount of PAR interception was not affected during the growing season. DI significantly reduced the seasonal ET in both years (19.8% in 2016 and 26.6% in 2017). All the hybrids extracted more soil water (29 mm in 2016 and 27 mm in 2017) at I75 than at I100. Maize plants at I75 had greater water use efficiency (WUE) (1.68 kg m−3) than those at I100 (1.41 kg m−3). However, DI did not affect radiation use efficiency (RUE). In conclusion, DI at I75 maintained grain yield through improved soil water extraction and WUE but stable canopy radiation interception and RUE.

Optimal bed width for wheat following rice production with raised-bed planting in the Yangtze River Plain of China

Waterlogging is a major threat to wheat following rice production in the Yangtze River Plain, China, where the raised-bed planting (RBP) pattern is recommended to reduce yield losses from waterlogging. Furrows used in RBP allow drainage runoff, and beds serve as planting zones. However, the optimal bed widths for wheat following rice cultivation are unknown. To adopt the most effective RBP patterns, we evaluated the effects of bed width on the volumetric soil water content (VSWC), radiation use efficiency, yield and profitability among different RBP patterns during the 2019/20 and 2020/21 growing seasons. The experiment comprised six planting patterns: conventional flat planting (FP) and five RBP patterns with different bed widths (RBP60, RBP120, RBP180, RBP240 and RBP300). The results demonstrated that VSWC increased with increasing bed width and RBP decreased VSWC in the 0–10 cm soil layer, but VSWC did not significantly decrease when the beds were excessively wide. The improved soil conditions promoted wheat canopy development and the fraction of photosynthetically active radiation (fPAR), which resulted in a significantly higher value of intercepted photosynthetically active radiation (IPAR) that eventually increased both grain yields and net revenue. The increase compared to FP was greatest for RBP180 and RBP240. There were tradeoffs between the positive growth-promoting effects and the negative effect of decreased planting area with RBP. Excessively wide beds reduced the advantages of water drainage, and excessively narrow bed widths reduced radiation resource capture. The optimal bed widths for wheat production on the Yangtze River Plain were 213.4–215.3 cm, 204.2–211.4 cm, 197.3–206.5 cm and 204.9–214.6 cm for IPAR, biomass, yield and economic benefits, respectively. Overall, RBP patterns with a 200.0-cm-bed and 25.0-cm-wide furrows are optimal for wheat after rice production under the current amount of rainfall in the Yangtze River Plain.

Reproductive biology of Myrtillocactus geometrizans (Cactaceae) flowers with contrasting orientation

AbstractIn columnar cacti, a higher production of reproductive structures on branches oriented towards the Equator has been explained by their higher interception of photosynthetic active radiation (PAR) as well as resource availability. The goal of this study was to evaluate the effect of orientation on diverse aspects of the reproductive biology of Myrtillocactus geometrizans. Phenology was studied in north‐ and south‐facing branches. Floral cycle events, floral visitors, reproductive traits associated with sexual and attraction functions, and reproductive success were estimated from reproductive structures with contrasting orientation. Pollination experiments were conducted to evaluate the effect of orientation on mating system. Our results showed that south‐facing branches had a longer duration of the mature fruit phenophase. Moreover, flower synchrony, production of reproductive structures, and floral traits associated with the male (number of anthers and pollen grains per floral bud), female (number and size of ovules and dimensions of both ovary and ovary cavity), and attraction (petal size) functions had higher values in south‐facing flowers. The beginning and ending of the male function and the end of flower anthesis occurred earlier in south‐facing flowers. Diversity of floral visitors was similar between orientations, except for beetles whose abundance was greater in flowers oriented towards the south. North‐ and south‐facing flowers had a mixed mating system, with similar reproductive success. Our results showed strong differences in the reproductive biology of an intertropical columnar cactus, probably in response to the uneven PAR interception and resource availability in branches and flowers with contrasting orientation.

Integrated Crop Management Practices Improve Grain Yield and Resource Use Efficiency of Super Hybrid Rice.

Super hybrid rice genotypes have transformed the rate of genetic yield gain primarily due to intersubspecific heterosis, although the physiological basis underpinning this yield transformation has not been well quantified. We assessed the radiation use efficiency (RUE) and nitrogen use efficiency (NUE) of novel hybrid rice genotypes under four management practices representative of rice cropping systems in China. Y-liangyou 900 (YLY900), a new super hybrid rice widely adopted in China, was examined in field experiments conducted in Jingzhou and Suizhou, Hubei Province, China, from 2017 to 2020. Four management practices were conducted: nil fertilizer (CK), conventional farmer practice (FP), optimized cultivation with reduced nitrogen (OPT–N), and optimized cultivation with increased nitrogen (OPT+N). Yield differences across the treatment regimens were significant (p < 0.05). Grain yield of OPT+N in Jingzhou and Suizhou were 11 and 12 t ha–1, which was 14 and 27% greater than yields obtained under OPT–N and FP, respectively. Relative to OPT–N and FP, OPT+N had greater panicle numbers (9 and 18%), spikelets per panicle (7 and 12%), spikelets per unit area (17 and 32%), and total dry weight (9 and 19%). The average RUE of OPT+N was 2.7 g MJ–1, which was 5 and 9% greater than that of OPT–N and FP, respectively, due to higher intercepted photosynthetically active radiation (IPAR). The agronomic efficiency of applied N (AEN) of OPT+N was 17 kg grain kg–1 N, which was 9 and 68% higher than that of OPT–N and FP. These results show that close correlations exist between yield and both the panicles number (R2 = 0.91) and spikelets per panicle (R2 = 0.83) in OPT+N. We conclude that grain yields of OPT+N were associated with greater IPAR, RUE, and total dry matter. We suggest that integrated cropping systems management practices are conducive to higher grain yield and resource use efficiency through expansion of sink potential in super hybrid rice production.

Loose and tower-type canopy structure can improve cotton yield in the Yellow River basin of China by increasing light interception

ABSTRACT Determining the optimal plant architecture and canopy structure are important objectives in research on the breeding and cultivation of high-yielding crops. To address this challenge, a field experiment was conducted in Anyang, Henan, China, to assess cotton light interception, boll spatial distribution, leaf area index (LAI), plant height and biomass, lint yield and yield component during 2018–2019. Treatments including 10 cotton cultivars with belong to tower-shaped and tube-type canopy structure. Compared with compact cotton varieties, the loose and tower-shaped cotton varieties intercepted more light (average 28.6%) and had a higher LAI (average 34.2%), resulting in a higher cotton yield (average 14.8%). In addition, polynomial correlation showed that the maximum light interception rate occurred at the flowering and boll-forming stage, when the annual mean plant height (94.6 cm), LAI (3.58) and biomass (15,006 kg ha−1) all reached their peak. Moreover, yield was extremely significantly positively correlated with intercepted photosynthetically active radiation (IPAR) (R = 0.7) and positively correlated with light use efficiency (LUE) (R = 0.36). Overall, the results suggest that cotton cultivars with loose and tower-type canopy structures intercept more light and should be planted to increase cotton yield and LUE in the Yellow River basin of China and areas with similar conditions.

Forecasting rainfed rice yield with biomass of early phenophases, peak intercepted PAR and ground based remotely sensed vegetation indices

Rice is the main staple food of the country but crop productivity in some years declines due to erratic monsoon and non-uniformity in spatial and temporal distribution of rainfall. Hence, assessing productivity of the rice crop in advance using meteorological and plant physiological attributes will be helpful for planners to take decision on contingency measures. In this investigation, dry biomass of early phenophases (active tillering, panicle initiation, boot leaf stages, flowering),peak intercepted photosynthetically active radiation (IPAR), peak spectral reflectance based vegetation indices of 3 rice varieties under 3 nitrogen levels (50, 100 and 130 kg ha-1) were made correlated with grain yield.Based on interrelationship it was found that biomass of flowering period was better correlated with grain yield with the R2 value of 0.75.Inter-relationship between peak IPAR(%), remotely sensed peak simple ratio index (IR/R) and normalized difference vegetation index (NDVI)with the rice yield were also established. Multiple regression modelwas developed by interrelating yield as dependant variable with dry biomass of flowering stage, peak IPAR(%) and peak IR/R and NDVI as independent variables which may be used as an effective tool for early prediction of rice yield, at least 30-40 days in advance. The grain yield was also estimated through developed algorithm using MODIS satellite derived NDVI and compared with that of actual yield.

The effect of strip orientation and width on radiation interception in maize–soybean strip intercropping systems

AbstractMaize–soybean intercropping systems are widely used in developing countries, but few studies have been performed to optimize such systems. The effects of strip width and orientation on photosynthetically active radiation (PAR) distribution characteristics were therefore determined to gain a better understanding of crop productivity in maize–soybean intercropping systems. A series of intercropping experiments incorporating different strip orientations and widths were conducted. In addition, an improved radiation transmission model was used to simulate PAR interception by the maize and soybean crops. We found that more PAR was intercepted by the soybean plants than by the maize plants when the strip orientation angle increased from 0° to 90° in the maize–soybean intercropping systems. This result was obtained in most of the main maize production areas, including those with different latitudes. The effect of strip widths within the intercropping systems also had a significant effect on PAR interception. The relative fraction of PAR intercepted ranged from 39.4% to 86% for soybean and 105.8% to 169.3% for maize. The effect of soybean strip width on leaf PAR interception was greater than that of maize strip width. These results are not only of fundamental biological importance but they also have important implications for agriculture in terms of the optimization of production in intercropping systems.

Optimum Planting Density Improves Resource Use Efficiency and Yield Stability of Rainfed Maize in Semiarid Climate.

Increasing planting density is an effective strategy for improving maize productivity, but grain yield does not increase linearly with the increase in plant density, especially in semiarid environments. However, how planting density regulates the integrated utilization of key input resources (i.e., radiation, water, and nutrients) to affect maize production is not clear. To evaluate the effects of planting density and cultivar on maize canopy structure, photosynthetic characteristics, yield, and resource use efficiency, we conducted a successive field experiment from 2013 to 2018 in Heyang County (Shaanxi Province, China) using three different cultivars [i.e., Yuyu22 (C1), Zhengdan958 (C2), and Xianyu335 (C3)] at four planting densities [i.e., 52,500 (D1), 67,500 (D2), 82,500 (D3), and 97,500 (D4) plants ha–1]. Increasing planting density significantly increased the leaf area index (LAI) and the amount of intercepted photosynthetically active radiation (IPAR), thereby promoting plant growth and crop productivity. However, increased planting density reduced plant photosynthetic capacity [net photosynthetic rate (Pn)], stomatal conductance (Gc), and leaf chlorophyll content. These alterations constitute key mechanisms underlying the decline in crop productivity and yield stability at high planting density. Although improved planting density increased IPAR, it did not promote higher resource use efficiency. Compared with the D1 treatment, the grain yield, precipitation use efficiency (PUE), radiation use efficiency (RUE), and nitrogen use efficiency (NUE) increased by 5.6–12.5%, 2.8–7.1%, and −2.1 to 1.6% in D2, D3, and D4 treatments, respectively. These showed that pursuing too high planting density is not a desirable strategy in the rainfed farming system of semiarid environments. In addition, density-tolerant cultivars (C2 and C3) showed better canopy structure and photosynthetic capacity and recorded higher yield stability and resource use efficiency. Together, these results suggest that growing density-tolerant cultivars at moderate planting density could serve as a promising approach for stabilizing grain yield and realizing the sustainable development of agriculture in semiarid regions.

Effect of mulching, row direction and spacing on microclimate and wheat yield at Ludhiana

The field experiments were conducted in rabi seasons of 2014-15 and 2015-16 at research farm, Ludhiana, Punjab. Wheat variety (WH 1105) was sown in two row directions viz, east-west (E-W) and north-south (N-S) with three row spacing as S1 (15 cm), S2 (22.5 cm) and S3 (30 cm), and two mulching levels viz., Mo (No mulch) and M1 (mulch at the rate of 5t ha-1). PAR interception, canopy temperature, soil temperature and soil moisture were recorded periodically during the crop season in all the treatments. The results revealed that the intercepted photosynthetically active radiation (PAR) was 4- 5 per cent higher in E-W than N-S row direction which contributed 1.67 q ha-1 higher grain yield. Better utilization of solar radiation was observed in 15.0 cm row spacing and the canopy temperature was 0.5°C higher in unmulched crop as compared to mulched crop during both years. Straw mulching @ 5t ha-1 improved soil moisture and regulated soil temperature. Mean soil temperature was higher (1.0 ºC) under mulched crop as compared to unmulched crop. The soil moisture was 4-5 per cent higher under mulched crop as compared to unmulched crop which ultimately resulted in higher soil temperature during early growth stages. Significantly higher grain yield was recorded in mulched crop as compared to unmulched.

Influence of cutting management on photosynthetic parameters, heat use efficiency and productivity of barley (Hordium vulgare L.) under variable sowing dates

Field experiments were conducted during 2015–16 and 2016–17 at Punjab Agricultural University, Ludhiana, to study the effect of staggered sowing on photosynthetic parameters, heat use efficiency and the productivity of barley (Hordium vulgare L.) in relation to different cutting management. The experiment was laid out in split plot design with three sowing dates (October 15, October 30 and November 15) in main plots and five cutting management [un-cut (control), cut at 50 days after sowing (DAS), cut at 60 DAS, cut at 50 DAS + additional 15 kg N ha-1 after cut (N15) and cut at 60 DAS + additional 15 kg N ha-1 after cut (N15)] in sub plots,replicated four times. The results indicated that photosynthetic parameters (PAR interception, chlorophyll index and normalized difference vegetation index) decreased significantly and progressively with each delay in sowing. Heat use efficiency and helio thermal use efficiency of October 15 and October 30 sown crops were statistically similar. Delay in sowing caused significant reduction in fodder, grain and biological yield of barley probably due to significant reduction in photosynthetic parameters.Nitrogen application after fodder cut improved the chlorophyll index, whereas, cutting did not influence the normalized difference vegetative index (NDVI).Un-cut crop recorded higher PAR interception.Significantly higher heat use efficiency and helio thermal use efficiency were recorded in uncutcrop. Un-cut and fodder cut at 50 DAS produced similar grain and biological yield and significantly higher than other cutting treatments. Cut at 60 DAS gave higher fodder yield but at the cost of 9.43-18.3 per cent reduction in grain yield than cut at 50 DAS. Correlation studies indicated significant positive correlation of grain yield with photosynthetic parameters, emphasizing the importance of higher growth and photosynthetic rate during reproductive period for best yield accrual from barley.

Effect of planting time and plant growth habits on phenological, physiological traits and associated with seed yield in African sarson (Brassica carinata)

An experiment was conducted during two consecutive years to study the effect of planting times (15 October, 5 November and 25 November) and cultivars differing for growth habits (BJC-13-1, BJC-13-2, BJC-13-3, BJC-13-4) newly developed determinate type and (PC-5 indeterminate variety) on phenology and physiological traits of African sarson (Brassica carinata A. Braun). The experiment was laid out in split plot design with three replications keeping planting times in main plot and genotypes in sub-plots. Planting time had a significant influence on both phenology and physiological traits of African sarson. The early sown crop took less number of days (66) for flowering while late sown crop took more number of days (79). There was drastic reduction in flowering period (20.8days), siliquing duration (23.3days) and reproductive phase(27.2days). Early planted (15 October) cultivars intercepted more PAR, higher LAI and SPAD-chlorophyll values resulting in higher yield. The interactive effects of planting dates and the cultivars were significant (p &lt; 0.05) for most of the features, which showed variable trends for the changes in the cultivars in response to planting dates. In all the cultivars, there was considerable deterioration in most of the studied traits due to delayed planting. Seed yield had positive association with siliquae duration (0.436), reproductive phase (0.426), SPAD (0.540*) and LAI (0.701**) with first planting (15 October) whereas with late planting (5 November) correlation existed between seed yield and LAI (0.073) and PAR interception (0.086) while with only flowering duration (0.772**) with 25 November sowing.

Altering microclimate of wheat (Triticum aestivum L.) by adjusting sowing dates, irrigation and nitrogen application in semi-arid and arid agroclimatic conditions of Punjab

Field experiments were conducted during rabi seasons of 2017-18 and 2018-19 and results of both the years were pooled to evaluate the microclimate of wheat under five dates of sowing, two nitrogen and two irrigation levels at Ludhiana and Bathinda representing semi-arid and arid agroclimatic regions of Punjab. Soil temperature reported during seed emergence was maximum in early sown (20th October) crop and decreased with delay in sowing at both the locations under study. Canopy temperature from 60 DAS onwards was recorded lower in 5th November and higher in 20th December sown crop while in case of irrigation and nitrogen levels, it was lower under optimal irrigation (I1) and recommended nitrogen (N1) application. Stress degree days (SDD) calculated were also lowest in 5th November sown crop (-323.6oC) and these were lower in N1 (-271.3oC) and I1 (-274.9oC) during both the years, respectively. Better crop growth and hence, leaf area index resulted in higher PAR interception in October sown with optimal irrigation and recommended nitrogen level. Canopy temperature at different periodic intervals (75, 90, 105 and 120 DAS) showed negative correlation with grain yield (R2 = 0.76, 0.75, 0.71 and 0.70, respectively). Similarly, SDD had negative relation with wheat yield (R2 = 0.74).