Photosynthetically Active Radiation Interception Research Articles

Soil temperature, PAR interception and crop phenology of maize (Zea mays L.) as influenced by straw mulching and herbicides

Soil temperature, PAR interception and crop phenology of maize (Zea mays L.) as influenced by straw mulching and herbicides

LAI and PAR interception in maize as influenced by fertilizer management in Punjab

Maize (Zea mays L.) is one of the most versatile cereal crops and widely cultivated in more than 150 countries of the world including tropical and temperate regions. Though maize can be grown in the wide range of climatic conditions, its productivity is largely depending on the prevailing weather conditions throughout the life cycle of the crop. Different management practices as well as prevailing weather parameters affect growth and development of crop differently. Therefore, it was contemplated to have an insight on the effect of photosynthetically active radiation (PAR) interception and leaf area index of maize grown under different nutrient management practices in Punjab

Growth, crop phenology and PAR interception in kharif maize (Zea mays L.) as influenced by planting methods and nitrogen levels

A field experiment was conducted at Punjab Agricultural University, Ludhiana during kharif 2015 to study the influence of three planting methods (flat, ridge and bed planting) and five nitrogen levels (0, 90, 120, 150 and 180 kg N/ha) on the growth, phenology and PAR interception in kharif maize. Bed planting method produced significantly higher LAI, DMA, leaf chlorophyll content, cob length, cob girth, number of rows per cob and grain yield of maize as compared to flat sowing method but was statistically at par with ridge planting method. Maximum PAR interception of 78.2% was registered at 90 DAS when the crop was raised on beds. Tasselling, silking and physiological maturity were enhanced by 2.3 to 2.5, 3.3 to 3.7 and 2.2 to 2.6 days, respectively, under bed and ridge planting methods as compared to flat sowing method. Application of 150 kg N/ha recorded significantly higher LAI, DMA, leaf chlorophyll content, PAR interception, cob length, cob girth, number of rows per cob and grain yield over 120, 90 and control but at par with 180 kg N/ha. Maximum PAR interception of 82.8% was observed with application of 180 kg N/ha at 90 DAS which was significantly higher than 0, 90 and 120 kg N/ha but was at par with 150 kg N/ha. Nitrogen application enhanced the tasselling and silking stages but delayed the physiological maturity stage.

Solar radiation use efficiency of pigeon pea (Cajanus cajan L.) in relation to crop geometry and varieties

Pulses are integral part of Indians diet so there is significant need to improve the productivity of pulses for their per capita availability. A research experiment was conducted in kharif 2015, at student research farm, Punjab Agricultural University, Ludhiana, Punjab to assess the radiation utilization and productivity of pigeon pea with respect to different row spacings and varieties. It was found that 60 x 21cm gave significant results in photosynthetically active radiation interception (PARI), canopy temperature, yield and yield components which were due to efficient GDD than other crop geometries. Similarly, determinate variety AL 15 performed significantly better than indeterminate variety PAU 881 in yield contributing components, yield and radiation use efficiency.

Radiation use efficiency of winter wheat in different planting patterns and irrigation frequencies in the North China Plain

ABSTRACTWinter wheat grain yield is connected with radiation use efficiency (RUE). A suitable planting pattern and irrigation strategy are essential for optimizing RUE. In order to investigate the effects of planting patterns and irrigation frequency on winter wheat RUE, a field study was conducted with two planting patterns and three irrigation frequencies. The two planting patterns were wide-precision (WP) and conventional-spacing (CS). The three irrigation frequencies were irrigated 120 mm at jointing stage, 60 mm each at jointing and heading stages, and 40 mm each at jointing, heading, and milk stages. The results showed leaf area index (LAI) was significantly (P < 0.05) higher in WP than in CS. In addition, the LAI in WP decreased with the increase in irrigation frequency. Under the same irrigation frequency, the photosynthetic active radiation (PAR) interception and dry matter were higher in WP than in CS. In WP, reduced irrigation frequency significantly increased the PAR interception at 60 cm above the ground surface. The largest grain yield and highest RUE was found in WP when plants were irrigated twice. The results indicate WP in combination with irrigated 60 mm each at jointing and heading stages maximized the winter wheat grain yield and RUE.

Nitrogen rate and plant density interaction enhances radiation interception, yield and nitrogen use efficiency of mechanically transplanted rice

With the development of hybrid rice cultivars and mechanized planting technologies, it is hypothesized that the grain yield and nitrogen (N) use efficiency of mechanically transplanted rice could be further improved by harnessing the compensatory effects from the N rate and plant density on individual plants and populations. We evaluated the interactive effects of the N rate and plant density on the grain yield and N use efficiency of rice in two field experiments during 2014 and 2015. The results indicated the significant interaction between the N rate and the plant density on the grain yield. The application of 165 kg N ha−1 along with a plant density of 24–27 × 104 hills ha−1 significantly increased the grain yield. A correlation analysis showed that the spikelet per hectare had a strong correlation with the grain yield. With an increase in the plant density, the N recover efficiency (NRE) was increased by 12.7–40.0% in 2014. However, the higher plant density, as in 33 × 104 hills ha−1 (D33), decreased the NRE by 5.8% in 2015. The N rate and plant density also significantly influenced the leaf area index (LAI) and the interception of photosynthetically active radiation (IPAR), the two important factors for grain yield formation. The LAI values of the 82.5 kg N ha−1 (N82.5), 165 kg N ha−1 (N165) and 82.5 kg N ha−1 (N247.5) treatments was increased by 26.3%, 101.4% and 116.0%, respectively, compared with that of the 0 kg N ha−1 (N0) treatment. Similarly, the LAI of the 21 × 104 hills ha−1 (D21), 27 × 104 hills ha−1 (D27) and D33 was increased by 17.8%, 20.5% and decreased by 12.8%, respectively, compared with that of 15 × 104 hills ha−1 (D15). The highest LAI was recorded when N247.5 was combined with D27. The N application increased the photosynthetically active radiation (IPAR) by 4.1%, 12.4% and 14.4%, respectively, compared with that of the N0 treatment. However, the IPAR increased by 0.8%, 2.6% and 3.3%, respectively, in comparison with that of D15. A moderate increase in the IPAR significantly increased the grain yield, while too much IPAR decreased the photosynthetically active radiation use efficiency (PARUE), leading to the lower synthesis of photosynthetic products. Hence, various combinations of the N rate and plant density are practicable for reducing the N inputs in addition to improving the grain yield and NRE.

Can mulching of maize straw complement deficit irrigation to improve water use efficiency and productivity of winter wheat in North China Plain?

Improving resource-use efficiency is vital for sustainable agricultural production and food security in water-scarce regions such as North China Plain. The aim of this study was to assess the effects of irrigation and straw-mulch on accumulated intercepted photosynthetically active radiation (AIPAR), radiation-use efficiency (RUE) and water-use efficiency (WUE) of wheat. A two-factorial field experiment was carried out at Luancheng Research Station (China) during 2015–16 and 2016–17. The factors included three irrigation levels – full (FI), deficit (DI) and partial root-zone drying (PRD), which besides rainfall received 200, 100 and 100 mm of irrigation, respectively, and two mulching strategies – mulch and no-mulch: ∼8 and 0 Mg ha−1, respectively. The results showed that mulch reduced AIPAR (6–11%) and increased RUE for total aboveground dry biomass (3–9%). Mulch affected intercepted photosynthetically active radiation (IPAR) between the tillering and anthesis stages, largely because of reduced soil surface temperature (0.8–1.5 °C), which led to delayed growth/development and impaired light interception. No significant difference was observed between DI and PRD for grain yield; however, effects on WUE varied during the two seasons. DI led to higher WUE during season I compared to PRD, while PRD resulted in highest WUE during season II. AIPAR was reduced under DI and PRD; however, RUE remained unaffected for irrigation treatments. The complementary effects of mulch were observed only under DI where WUE was increased by 4–6%. The results imply that the PRD irrigation under field conditions is not as effective as it has been anticipated, especially in soils with high clay content. Mulch induced reduction in growth/development tends to nullify its positive effects through water conservation. Taken together, these results reiterate the need to further optimize mulching and PRD irrigation practices before recommending their use under field conditions, especially for small grain cereals.

Growth, N uptake and N critical dilution curve in broccoli cultivars grown under Mediterranean conditions

Adequate nitrogen (N) availability must be ensured in broccoli as it is a high N demand crop, however the N not taken up may cause ground and surface water pollution. Both species-specific growth and N demand predicting models could be useful for rational N fertilization management.Two field experiments were conducted on three broccoli cultivars grown at different N fertilization levels [0 (N0), 75 (N75), and 100 (N100) kg ha−1] and under Southern Italian/Mediterranean conditions (i) to study the growth and the N uptake and (ii) to determine the critical N dilution curve for this crop. Nitrogen fertilization prompted crop growth during the linear phase (growth rate ∼9.0 g m-2 d-1 of dry weight - DW) as a result of the enhancement of the intercepted photosynthetically active radiation (IPAR) and of the efficiency in using IPAR for producing dry biomass (RUE). However, the effect of N fertilization on final aboveground dry biomass production (ADW) (∼4.6 Mg ha-1) was affected by the cultivar specific response to the seasonal variability of the temperature time course. In the ‘Ironman’ cultivar, N nutrition was less effective under suboptimal temperatures, in enhancing ADW and N uptake, because of the reduced leaf growth and IPAR. On the contrary, in ‘Naxos’ and ‘Parthenon’ N fertilization was more effective in limiting the effect on plant growth of the sub-optimal temperatures. Under such conditions, despite a slow reduction in IPAR, both cultivars enhanced RUE, with a concomitant increase in specific leaf N. ‘Naxos’ and ‘Parthenon’ gave higher and more stable yields, ADW, harvest index (HI) and N uptake over the two seasons. Among the N rates, the best N use efficiency in terms of yield (Partial Factor Productivity) and head dry weight gain (Agronomical NUE) per unit of applied N fertilizer, was obtained with the rate of 75 kg ha-1. At the highest N rate, ADW and yield slightly increased, with no effect on HI. Hence, this rate might be considered close to the optimal under the conditions of the experiment.Two cultivar-specific N dilution curves for broccoli have been proposed to account for the difference which emerged between’ Parthenon’ and the other broccoli cultivars mainly for the differences related to the proportion of stems on ADW. Both curves underline that this crop maintains a relatively high fraction of photosynthetically active tissue approaching the harvest compared to other brassicas.

Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain

In order to promote the winter wheat yield and guarantee seeding quality in double-cropping system, no-tillage or reduced tillage planting modes with different row spacing have been implemented to result in different levels of yield. A three-year (2012-2015) field experiment was conducted on the experimental farm at Zhuozhou of Hebei Province in North China Plain to compare winter wheat yield from the two planting modes: wide-narrow row space planting mode (WN) and uniform row space planting mode (UR) Both planting modes were performed under reduced tillage conditions with straw mulching. The results showed that in North China Plain WN had positive impacts on crop yield, yield components, leaf area index (LAI) and intercepted photosynthetically active radiation (IPAR) index. Comparing with the UR, IPAR and LAI index for WN were enhanced by 4.8% and 5.2%, respectively. The average yield for WN was 7.2%, significantly greater than that of UR under the same quantity and density. In addition, for WN mode, machinery could pass through with less blocking under large amount of straw mulching, which largely improved tillage efficiency and potentially popularized the conservation tillage technology in North China plain. It is therefore recommended that wide-narrow row space planting mode (WN) combined with reduced tillage and straw mulching be more suitable for conservation tillage in double-cropping pattern areas in North China Plain. Keywords: winter wheat yield, wide-narrow seeding, conservation tillage, row spacing, LAI, IPAR DOI: 10.25165/j.ijabe.20181104.3399 Citation: Hu H N, Lu C Y, Wang Q J, Li H W, He J, Xu D J, et al. Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain. Int J Agric & Biol Eng, 2018; 11(4): 74–80.

Source-sink optimization and morpho-physiological response of soybean [Glycine max] to detopping and mepiquat chloride application

Effect of detopping and mepiquat chloride on morphological, physiological and yield attributes of soybean cultivar ‘SL 544’ was studied. A two year investigation was conducted at Punjab Agricultural University, Ludhiana, during kharif seasons of 2014 and 2015. The experiment was laid-out in randomized complete block design (RCBD) with eight treatments viz. control, detopping (removal of 4-5 cm apical portion of main stem) at 50-55 days after sowing (DAS), mepiquat chloride @ 200 ppm (50-55 DAS), mepiquat chloride @ 200 ppm (50-55 + 65-70 DAS), mepiquat chloride 250 ppm (50-55 DAS), mepiquat chloride @ 250 ppm (50-55 + 65-70 DAS), mepiquat chloride @ 300 ppm (50-55 DAS) and mepiquat chloride @ 300 ppm (50-55 + 65-70 DAS) with four replications. Detopping had a non-significant effect on leaf area index, SPAD value, PAR interception, abscission of reproductive parts, seeds per pod, 100-seed weight, pod length and stover yield of soybean. It significantly decreased plant height, increased total dry matter accumulation/plant, number of flowers and pods/plant, pod setting percentage and seed yield over control during 2014 and 2015. At crop harvest, detopping developed optimized source-sink relationship by means of distribution of total dry matter between stem, foliage and pods by 20.4, 14.9 and 64.6 % during 2014 while 22.6, 20.1 and 57.4 % during 2015, respectively. Mepiquat chloride posed a non-significant effect on plant height, PAR interception, number of flowers/plant, number of seeds/pod, pod length and stover yield of soybean but it significantly decreased leaf area index, abscission of reproductive parts while increased the dry matter accumulation/plant, number of pods/plant, 100-seed weight and seed yield relative to control. At harvest, two foliar applications of mepiquat chloride @ 250 ppm resulted in optimized source-sink relationship by the distribution of total dry matter among stem, foliage and pods by 20.6, 10.9 and 68.5 % during 2014 while 19.5, 7.6 and 72.9 % during 2015, respectively. Occurrence of more rainfall during 2015 as compared to 2014 caused mepiquat chloride to hike seed yield as compared to detopping which is clearly witnessed by increase in pod dry weight per plant during 2015 than 2014. Conclusively, both detopping and mepiquat chloride resulted in enhancement in source-sink relationship and seed yield of soybean.

Sorghum radiation use efficiency and biomass partitioning in intercrop systems

The objective of intercropping is to improve resource efficiencies for land, water and radiation. Few studies have focused on the interactive effects of water stress on radiation use efficiency (RUE) in an intercrop system. The study determines the effect of intercropping sorghum with either cowpea or bottle gourd on RUE and biomass accumulation in response to water stress. This was assessed using a split-plot design with crop sequences sole sorghum, sole cowpea, and sole bottle gourd and intercrop systems sorghum–cowpea and sorghum–bottle gourd assigned as sub-plots arranged in randomised complete blocks within main plots, water regimes: full irrigation, deficit irrigation and rainfed. We quantified specific leaf area, leaf area index as well as biomass accumulation and partitioning. Extinction coefficient, intercepted photosynthetic active radiation (IPAR) and RUE for biomass (RUEb) and grain (RUEg) were also determined. Under rainfed conditions, intercropping with either cowpea (26%) or bottle gourd (62%) improved sorghum leaf area. A reduction in specific leaf area was observed for sorghum when it was intercropped with either cowpea (−20%) or bottle gourd (−19%). Under full irrigation, sorghum stems constituted a larger proportion (62%) of final biomass in comparison to sorghum under deficit irrigation (52%) and rainfed conditions (50%). Intercropping sorghum with either cowpea or bottle gourd improved IPAR (38%), RUEb (93%) and RUEg (11%) under rainfed conditions. This study showed that under water-limited conditions intercropping reduced sorghum stem mass and increased canopy size, radiation interception, and grain yield and improved RUE. In agreement with our proposition, water availability was closely associated with radiation use efficiency. Intercropping can be recommended for semi-arid environments since it improves RUE and sorghum biomass and grain yield.

Influence of primed seed and varying seed rate on growth and productivity of soybean (Glycine max L.) under different planting techniques

An experiment was conducted at Punjab Agricultural University, Ludhiana during 2015 and 2016 to study the effect of priming, different seed rate on growth and seed yield of soybean planted under bed and flat method. The study was planned in factorial split plot design, keeping two planting techniques (flat sowing and bed sowing) and two seed priming treatments ( non primed seeds and 100 ppm GA3 primed seeds) in main plot and three seed levels ( 50, 62.5 and 75 kg ha-1) in sub plot. The objective of the study was to evaluate the effect of seed priming on growth and productivity under different planting techniques with the use of varying seed rates. The results revealed that growth attributes viz. emergence count, plant height, dry matter accumulation, leaf area index and photosynthetic active radiation interception (%) was significantly higher under bed planting technique as compared to flat sowing method. The pooled seed yield was increased by 15.6 % in bed planted soybean crop as compared to flat planted crop. Soybean seeds primed with 100 ppm GA3 recorded significant results in all the growth parameters. Primed seed recorded increase in yield 15.3 % than non primed seeds. Seed rate of 62.5 kg ha-1 recorded significantly higher emergence count, plant height, dry matter accumulation, leaf area index and photosynthetic active radiation interception (%) which was statistically similar in results with 75 kg ha-1 seed rate in both the two years. Pooled seed yield of 62.5 kg ha-1seed rate was 4.61 % higher than 75 kg ha-1 and 12.6 % than 50 kg ha-1 seed rate.

Relationships among growth, δ13C, foliar nitrogen concentration, foliar nitrogen content and intercepted radiation at different cultural intensities, planting densities and site indices reveal the importance of water use efficiency in mid-rotation loblolly pine stands

Carbon isotope composition (δ13C), intercepted photosynthetically active radiation (IPAR), foliar nitrogen (N) content and foliar N concentration are all factors related to stand growth and productivity. The relationships between these attributes and growth were studied in 15 and 16-year-old loblolly pine (Pinus teada L.) stands at planting densities ranging from 1483 to 4448 tree ha−1 grown under two silvicultural management intensities, both having different fertilization inputs. Measurements were conducted on six sites in the lower and upper coastal plains of Florida, Georgia and Alabama at site indices (SI) (base age 25 years) ranging from 18.6 to 29.6 m. The effects of planting density, cultural intensity and SI on the aforementioned attributes were studied. Correlations between δ13C, foliar N concentration, foliar N content, IPAR and current annual increment (CAI) of stem volume, stem wood biomass, branch biomass, foliage biomass and total above-ground biomass were also studied. We hypothesized that foliar N would be a better predictor of growth than either δ13C or IPAR, and that IPAR would be the same across planting densities due to canopy closure.The results indicated that CAI of stem volume, stem wood biomass and total above-ground biomass were affected by SI or the interaction between SI and management intensity. The significant relationships between SI and CAI growth indices were all positive indicating greater growth at greater site indices. A negative correlation was found between δ13C, a surrogate for water use efficiency, and SI, meaning stands had lower water use efficiencies at sites with higher SI values. Foliar N concentration and content were both affected by silvicultural intensity, while IPAR was only affected by planting density. Among the physiological parameters, δ13C was the only parameter significantly correlated with the CAI indices. Significant negative correlations were found between CAI of stem volume, stem wood biomass, total above-ground biomass and δ13C. These results indicated that moisture availability affected growth of the highly fertilized mature stands in this study. The findings reported here, when compared to similar studies in younger stands, suggest that growth limitations shifted from light availability to soil moisture availability in older stands when nitrogen was not limiting.

Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain

In order to promote the winter wheat yield and guarantee seeding quality in double-cropping system, no-tillage or reduced tillage planting modes with different row spacing have been implemented to result in different levels of yield. A three-year (2012-2015) field experiment was conducted on the experimental farm at Zhuozhou of Hebei Province in North China Plain to compare winter wheat yield from the two planting modes: wide-narrow row space planting mode (WN) and uniform row space planting mode (UR) Both planting modes were performed under reduced tillage conditions with straw mulching. The results showed that in North China Plain WN had positive impacts on crop yield, yield components, leaf area index (LAI) and intercepted photosynthetically active radiation (IPAR) index. Comparing with the UR, IPAR and LAI index for WN were enhanced by 4.8% and 5.2%, respectively. The average yield for WN was 7.2%, significantly greater than that of UR under the same quantity and density. In addition, for WN mode, machinery could pass through with less blocking under large amount of straw mulching, which largely improved tillage efficiency and potentially popularized the conservation tillage technology in North China plain. It is therefore recommended that wide-narrow row space planting mode (WN) combined with reduced tillage and straw mulching be more suitable for conservation tillage in double-cropping pattern areas in North China Plain. Keywords: winter wheat yield, wide-narrow seeding, conservation tillage, row spacing, LAI, IPAR DOI: 10.25165/j.ijabe.20181104.3399 Citation: Hu H N, Lu C Y, Wang Q J, Li H W, He J, Xu D J, et al. Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain. Int J Agric & Biol Eng, 2018; 11(4): 74–80.

Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain

In order to promote the winter wheat yield and guarantee seeding quality in double-cropping system, no-tillage or reduced tillage planting modes with different row spacing have been implemented to result in different levels of yield. A three-year (2012-2015) field experiment was conducted on the experimental farm at Zhuozhou of Hebei Province in North China Plain to compare winter wheat yield from the two planting modes: wide-narrow row space planting mode (WN) and uniform row space planting mode (UR) Both planting modes were performed under reduced tillage conditions with straw mulching. The results showed that in North China Plain WN had positive impacts on crop yield, yield components, leaf area index (LAI) and intercepted photosynthetically active radiation (IPAR) index. Comparing with the UR, IPAR and LAI index for WN were enhanced by 4.8% and 5.2%, respectively. The average yield for WN was 7.2%, significantly greater than that of UR under the same quantity and density. In addition, for WN mode, machinery could pass through with less blocking under large amount of straw mulching, which largely improved tillage efficiency and potentially popularized the conservation tillage technology in North China plain. It is therefore recommended that wide-narrow row space planting mode (WN) combined with reduced tillage and straw mulching be more suitable for conservation tillage in double-cropping pattern areas in North China Plain. Keywords: winter wheat yield, wide-narrow seeding, conservation tillage, row spacing, LAI, IPAR DOI: 10.25165/j.ijabe.20181104.3399 Citation: Hu H N, Lu C Y, Wang Q J, Li H W, He J, Xu D J, et al. Influences of wide-narrow seeding on soil properties and winter wheat yields under conservation tillage in North China Plain. Int J Agric & Biol Eng, 2018; 11(4): 74–80.

Virtual Geographic Simulation of Light Distribution within Three-Dimensional Plant Canopy Models

Virtual geographic environments (VGEs) have been regarded as an important new means of simulating, analyzing, and understanding complex geological processes. Plants and light are major components of the geographic environment. Light is a critical factor that affects ecological systems. In this study, we focused on simulating light transmission and distribution within a three-dimensional plant canopy model. A progressive refinement radiosity algorithm was applied to simulate the transmission and distribution of solar light within a detailed, three-dimensional (3D) loquat (Eriobotrya japonica Lindl.) canopy model. The canopy was described in three dimensions, and each organ surface was represented by a set of triangular facets. The form factors in radiosity were calculated using a hemi-cube algorithm. We developed a module for simulating the instantaneous light distribution within a virtual canopy, which was integrated into ParaTree. We simulated the distribution of photosynthetically active radiation (PAR) within a loquat canopy, and calculated the total PAR intercepted at the whole canopy scale, as well as the mean PAR interception per unit leaf area. The ParaTree-integrated radiosity model simulates the uncollided propagation of direct solar and diffuse sky light and the light-scattering effect of foliage. The PAR captured by the whole canopy based on the radiosity is approximately 9.4% greater than that obtained using ray tracing and TURTLE methods. The latter methods do not account for the scattering among leaves in the canopy in the study, and therefore, the difference might be due to the contribution of light scattering in the foliage. The simulation result is close to Myneni’s findings, in which the light scattering within a canopy is less than 10% of the incident PAR. Our method can be employed for visualizing and analyzing the spatial distribution of light within a canopy, and for estimating the PAR interception at the organ and canopy levels. It is useful for designing plant canopy architecture (e.g., fruit trees and plants in urban greening) and planting planning.

Stability of a winter wheat population with high yield and high resource use efficiency

Using the winter wheat cultivar Tainong 18 as the experimental material, we analyzed yield stability from 2012 to 2016 under three different treatments: T1(following typical local field management practices), T2(high-yield: high nitrogen and water were supplied to foster high grain yield), and T3(high-yield, high-efficiency: optimized field management including increasing plant density, reducing nitrogen input and delaying of the sowing date). Yield related phenotypic traits, including the number of ears on the main stem and tillers, leaf area index (LAI), photosynthetically active radiation (PAR) interception, dry matter accumulation and distribution, as well as grain yield, were analyzed over four seasons to determine their relationships with annual radiation, accumulated temperature and precipitation. We then determined grain yield stability for each of the three treatments. The amount and distribution of radiation, accumulated temperature, and precipitation varied greatly within each season. The ears on the main stem represented 38.9%, 58.7%, and 66.9% of the total ears, respectively, for wheat grown in the T1, T2 and T3 treatments, indicating that T1 ears originated mainly from the tillers, T2 ears from both the main stem and the tillers, and T3 ears from the main stem. The T2 and T1 treatments produced the highest and lowest amount of dry matter and grain yield, respectively. Although having relatively lower dry matter accumulation at maturity compared with T2, T3 led to higher grain yield due to high LAI, high PAR interception and utilization, high net canopy photosynthetic rate from booting (especially from 14 days after anthesis) to maturity and a higher harvest index. Among the three treatments, T3 resulted in the lowest annual range, standard deviation, and coefficient of variation for LAI, PAR interception, and dry matter accumulation. Thus, grain yield was most stable in wheat grown in the T3 treatment mainly due to stability in biological production during all four seasons.

Radiation use efficiency and biomass partitioning to storage roots in fodder beet crops

Abstract Intercepted photosynthetic active radiation (IPAR), radiation use efficiency (RUE) and partitioning of dry matter (DM) to storage roots (proot, %) were quantified for fodder beet crops subjected to contrasting water (irrigated or rain-fed) and nitrogen (N; 0, 25, 50, 100 and 200 kg/ha) supply conditions in Canterbury, New Zealand. The objectives were to enhance the understanding of physiological processes controlling fodder beet response to abiotic stresses and also to estimate parameters for biophysical models that simulate crop growth. Data from three field experiments showed a wide range of fodder beet yield (14–29 t DM/ha) in response to water and N stress. These yield differences were mostly explained by the treatments effect on IPAR (650–1050 MJ PAR/ha), with relatively smaller responses in RUE and proot. For unconstrained (fully irrigated; ≥100 kg N/ha) growth conditions, maximum values were 3.6 g DM/MJ PAR for RUE and 78% for proot for total biomass at final harvest. The RUE for the rain-fed, 0 kg N/ha crops was reduced by up to 25%, while proot was only marginally reduced (∼3% in rain-fed crops) compared with crops under unconstrained growth conditions. While the RUE responded linearly to additional N supply in irrigated crops, rain-fed crops showed a more consistent decline in RUE across N fertiliser rates with 65–70% of unstressed values. High RUE values were observed across a wide range of crop N status (Nitrogen Nutrition Index [NNI] from 0.8 to 1.6) in irrigated crops. In contrast, RUE in rain-fed was low at high NNI estimates because of high N concentration in a smaller canopy area. The lower RUE in rain-fed crops was aligned with reduced leaf photosynthetic rates (Pnleaf) although there was a high variability in Pnleaf measurements. These results give a first quantification of IPAR, RUE, proot and Pnleaf in fodder beet. They provide insights on the relative sensitivity of fodder beet to water and N stresses. These results are valuable for the interpretation of crop responses and for setting parameters for biophysical models to simulate fodder beet growth.

Switchgrass Growth and Effects on Biomass Accumulation, Moisture Content, and Nutrient Removal

Core Ideas Quantifying intra‐seasonal fluctuations allows for simulating productivity trade‐offs. Biomass yields peaked August–September when N and K and moisture contents were elevated. Delaying harvests to late fall reduces fertilizer replacement needs. Temporal patterns of plant growth, composition, and nutrient removal impact development of models for predicting optimal switchgrass (Panicum virgatum L.) harvest times for bioenergy. Original time‐course data are needed to construct useful models. Objectives were to characterize seasonal trends in yield, tissue moisture, ash content, leaf area index (LAI), interception of photosynthetically active radiation (PAR), and macronutrient accumulation and losses. Plots were subjected to 12 single harvests May to February in 2009–2010 and 2010–2011. Biomass accumulation into late summer followed a sigmoidal function, reaching an asymptote at 14 Mg ha−1, concurrent with early seed filling. During both seasons, yields decreased 26 to 32% from September to February. Moisture content declined to levels appropriate for storage (≤200 g kg−1, wet basis) by 15 December. Interception of PAR plateaued at 96% in late July 2009 and mid‐June 2010, whereas LAI declined in early July both years. Peak N uptake occurred in August 2009 and July 2010 (80 and 141 kg N ha−1, respectively). Potassium uptake peaked in July 2009 (136 kg ha−1) and in June 2010 (180 kg ha−1). Phosphorus peaked in July and August 2009 and 2010 at 16 and 17 kg ha−1, respectively. Peak biomass yields occurred in August–September when N and K uptake and moisture contents were still elevated. Delaying harvests until late fall or winter reduced fertilizer replacement needs and moisture content, but a trade‐off in yield occurred. Quantifying these intra‐seasonal changes allows for simulating productivity trade‐offs and applying those to economic and environmental analyses.

Effect of nitrogen management modes on grain yield, nitrogen use efficiency and light use efficiency of wheat

A nitrogen management experiment with three nitrogen levels (0, 120, and 180 kg·hm-2, namely N0, N120, N180) and three nitrogen allocation modes (NA: base fertilizer 100%; NB: base fertilizer 70% + seedling fertilizer 30%; NC: base fertilizer 60% + jointing fertilizer 40%) was conducted at four sites (Chongqing, Renshou, Guanghan and Xichang) during two consecutive years, the SPAD value, canopy photosynthetic rate (CAP), photosynthetically active radia-tion (PAR) interception efficiency and grain yield were determined, and the nitrogen use efficiency and PAR use efficiency were calculated. The results showed that the SPAD of upper-most three leaves, CAP, PAR interception efficiency and grain yield were promoted with increasing nitrogen fertilizer, but nitrogen fertilizer use efficiency, productivity efficiency, uptake efficiency and use efficiency were decreased. The promoting effects of nitrogen fertilizer postponing were different among nitrogen levels, with the highest SPAD in N180 treatment and the highest CAP in N120 treatment. The light use efficiency of different nitrogen fertilization patterns differed among four sites. Furthermore, nitrogenous fertilizer postponing significantly increased nitrogen agricultural fertilizer use efficiency, productivity efficiency, uptake efficiency and apparent nitrogen recovery efficiency, but declined nitrogen use efficiency, and the performance of NC was better than NB. Among different sites, Guanghan had the highest SPAD, CAP, PAR interception efficiency and grain yield, Xichang had higher SPAD and nitrogen use efficiency, lower CAP and PAR use efficiency, Chongqing and Renshou had the lowest SPAD, light use efficiency, nitrogen use efficiency and grain yield. Biomass had significant positive relationships with grain yield, CPA, SPAD, and PAR interception efficiency. Therefore, the increase of nitrogen fertilizer could promote yield at all sites, and nitrogenous fertilizer postponing could further optimize grain yield component and improve nitrogen and light use effi-ciency. But the effects depended on the years and sites, thus a target nitrogen management mode should be site-specifically made.