Radiation Interception Research Articles

Contributions of radiation interception and radiation-use efficiency to biomass decrease due to potassium starvation depend on potassium deficiency intensities

Yield loss due to insufficient potassium fertilizer supply has been well documented; however, the information about the negative effect of potassium deficiency on crop yield caused by ecophysiological determinants is not enough. A field experiment with three K treatments (severe K deficiency treatment, K1; moderate K deficiency treatment, K2; and sufficient K supply treatment, K3) was conducted to (1) assess the effects of potassium deficiency on green leaf area index (GLAI) reduction; (2) quantify the contributions of single leaf area, leaf senescence, and leaf appearance to GLAI reduction under potassium deficiency; (3) reveal the changes in the contributions of accumulated radiation interception (RIacc) and radiation-use efficiency (RUE) to above-ground biomass (AM) decrease of oilseed rape under different K supplies. GLAI was restrained due to potassium deficiency, with a reduction ranging from 10.6 to 45.4%. The reduced single leaf area and accelerated leaf senescence caused by potassium starvation accounted for 5.9–23.7% and 2.4–29.0% reduction in GLAI, but delayed leaf appearance rate contributed little. The RIacc during the seedling stage in the K1, K2, and K3 treatments was 101.2, 110.7, and 120.0 MJ m− 2, respectively, and the RUE in the K1, K2, and K3 treatments was 1.03, 2.22, and 2.98 g MJ− 1, respectively, which caused a 61.7% and 48.2% reduction of the final harvested AM in the K1 and K2 treatments compared with the K3 treatment. When AM reduction was less than 24.8%, RIacc was the main determining factor; however, it transferred to RUE when biomass decreased more. In conclusion, GLAI decreased due to potassium starvation was mainly caused by the reduced single leaf area and accelerated leaf senescence, and the relative contribution of RIacc and RUE to AM decline was related to the degree of potassium deficiency.

Substituting green or far-red radiation for blue radiation induces shade avoidance and promotes growth in lettuce and kale

Although red (R; 600–700 nm) and blue (B; 400–500 nm) radiation can be sufficient for plants grown indoors, other wavebands such as green (G; 500–600 nm) and far red (FR; 700–800 nm) can also regulate photosynthesis, plant morphology, and secondary metabolism. The objective of this study was to determine how substitutions of B radiation with G and/or FR radiation influence growth of leafy greens grown indoors under light-emitting diodes (LEDs). We postulated G and/or FR radiation (and low B radiation) would trigger shade-avoidance responses and thus promote biomass accumulation through increased radiation interception. We grew lettuce (Lactuca sativa ‘Rex’ and ‘Rouxai’) and kale (Brassica oleracea var. sabellica ‘Siberian’) under warm-white (WW) LEDs at 180 μmol·m–2·s–1 (400–800 nm) for 9–11 days and then transplanted seedlings into a hydroponic system with ten different lighting treatments. The air temperature (20 °C), photoperiod (20 h), total photon flux density (180 μmol·m–2·s–1; 400–800 nm), and fertility were maintained the same across treatments. In addition to WW and equalized-white (EQW) controls, combinations of B (peak =449 nm), G (peak =526 nm), and FR (peak =733 nm) LEDs, each at 0, 20, 40, or 60 μmol·m–2·s–1, were delivered in a R background (peak =664 nm) of 120 μmol·m–2·s–1. One month after seed sow, we collected data on shoot mass, leaf morphology, and pigmentation. Substituting G or FR radiation for B radiation promoted leaf expansion and increased shoot mass but decreased chlorophyll concentrations in all crops. For example, lettuce ‘Rex’ grown under 60 μmol·m–2·s–1 of G +120 μmol·m–2·s–1 of R radiation was 38% greater in plant diameter and 54% greater in shoot dry mass compared to those under 60 μmol·m–2·s–1 of B +120 μmol·m–2·s–1 of R radiation. Substituting B radiation with G radiation at 60 μmol·m–2·s–1 also reduced red coloration of lettuce ‘Rouxai’. At the same photon flux density, FR radiation increased leaf expansion and decreased red foliage coloration more than G radiation. We conclude that substituting G and/or FR radiation for B radiation triggers shade-avoidance responses, accelerating plant growth while decreasing pigment concentrations.

Modelling soil hydrothermal regimes in pigeon pea under conservation agriculture using Hydrus-2D

Limited information is available about the effects of conservation agriculture (CA) practices on soil temperature moderation and distribution of water in the soil profile during crop growth, particularly on the changes in the components of water and energy balance. Hence, the objective of this study was to assess soil hydrothermal regimes and water and energy balance components in pigeon pea (Cajanas cajan) grown under CA in a pigeon pea-wheat (Triticum aestivum) cropping system using the Hydrus-2D model. There were seven treatments: permanent broad bed (PBB), PBB with crop residue (PBB + R), permanent narrow bed (PNB), PNB with crop residue (PNB + R), zero tillage (ZT), ZT with crop residue (ZT + R), and conventional tillage (CT). Results during the seventh year of the experiment showed that the PBB, PBB + R, PNB, PNB + R and ZT + R treatments significantly reduced surface soil bulk density (BD), increased field saturated hydraulic conductivity (Ksat) and improved soil water retention over the CT. The Ksat values obtained as the output of the Rosetta-Lite model which is implemented in Hydrus-2D) were very low. Hence, experimentally measured Ksat values were optimized along with parameters α and n that were obtained as output of the Rosetta Lite model, through inverse modelling (IM). The model predicted daily changes in profile soil water content (SWC) with reasonable accuracy (R2 = 0.77, RMSE = 0.012; n = 84). Soil water balance simulated from the model indicated higher cumulative transpiration (CTr), lower cumulative evaporation (CE) and higher soil water retention in the PNB + R and PBB + R plots than CT. Computed values of thermal conductivity (λ) obtained from the observed soil temperature (ST) data at different SWC values showed significant correlations with those optimized through IM. In general, Hydrus-2D model over-predicted the ST values during a simulation period of 10 days. However, reasonably accurate (R2 = 0.91, RMSE = 1.41 °C; n = 102) predictions were observed for the 0–20 cm soil layer using the optimized values. It was also observed that PBB + R and PNB + R treatments improved soil hydrothermal regimes, root growth, radiation interception, leaf area index and biomass production of the pigeon pea crop. Hydrus-2D used in this study could also satisfactorily simulate the temporal changes in energy balance components, such as soil heat flux (G) and evaporative heat flux (LE). Hence, this model may be adopted for evaluating arable management practices for characterizing different components of water and energy balance in pigeon pea.

Digital Image Analysis of Old World Bluestem Cover to Estimate Canopy Development

Core Ideas ImageJ and Canopeo agreed in accurately measuring vegetative ground cover of pasture. Light interception was linearly related to ground cover measurement with ImageJ and Canopeo. ImageJ and Canopeo reduced the time for estimating canopy development by 96%. ABSTRACTDigital image analysis (DIA) can potentially provide rapid, objective assessment of pasture canopy development. In pastures of ‘WW‐B.Dahl’ Old World bluestem [Bothriochloa bladhii (Retz) Blake], we compared the DIA programs ImageJ and Canopeo for ground cover estimates, their ability to estimate canopy functions, and their time savings for vegetation analysis relative to a manual method. The DIA procedure involved processing overhead canopy images into two color groupings corresponding to green ground cover and non‐green (dead) cover plus bare ground for ground cover calculation. ImageJ analysis of ground cover agreed with two types of Canopeo applications (r2 values of 0.97 and 0.98). The prediction regression for percentage photosynthetically active radiation interception (PARI) using ImageJ, y = 0.94x − 2.91 (r2 = 0.72), was not different from Canopeo. Predicted values of leaf area index (LAI) and biomass increased exponentially with ground cover, likely owing to overlapping leaf area in older canopies. Two‐dimensional ground cover had limited power of estimating LAI and biomass when ground cover exceeded 60%, LAI exceeded 1.8, and biomass exceeded 1500 kg DM ha−1. The time required for estimating PARI, LAI, and green biomass using ground cover from both DIA methods was reduced to 3.6% of manual methods. The use of DIA with ImageJ provided measurements of ground cover that are simple and conducive to large batch analyses. Regressions of ground cover were deemed useful for rapid estimations of PARI and LAI, but of lesser value for biomass, especially when canopies developed stems and seedheads.

Phytochrome B enhances plant growth, biomass and grain yield in field-grown maize.

Phytochrome B (phyB) is a photosensory receptor important for the control of plant plasticity and resource partitioning. Whether phyB is required to optimize plant biomass accumulation in agricultural crops exposed to full sunlight is unknown. Here we investigated the impact of mutations in the genes that encode either phyB1 or phyB2 on plant growth and grain yield in field crops of Zea mays sown at contrasting population densities. Plants of maize inbred line France 2 wild type (WT) and the isogenic mutants lacking either phyB1 or phyB2 (phyB1 and phyB2) were cultivated in the field during two seasons. Plants were grown at two densities (9 and 30 plants m-2), irrigated and without restrictions of nutrients. Leaf and stem growth, leaf anatomy, light interception, above-ground biomass accumulation and grain yield were recorded. At high plant density, all the lines showed similar kinetics of biomass accumulation. However, compared with the WT, the phyB1 and phyB2 mutations impaired the ability to enhance plant growth in response to the additional resources available at low plant density. This effect was largely due to a reduced leaf area (fewer cells per leaf), which compromised light interception capacity. Grain yield was reduced in phyB1 plants. Maize plants grown in the field at relatively low densities require phyB1 and phyB2 to sense the light environment and optimize the use of the available resources. In the absence of either of these two light receptors, leaf expansion is compromised, imposing a limitation to the interception of photosynthetic radiation and growth. These observations suggest that genetic variability at the locus encoding phyB could offer a breeding target to improve crop growth capacity in the field.

Applying high-resolution visible-channel aerial imaging of crop canopy to precision irrigation management

Canopy cover (or vegetation cover) maps serve in irrigation management mainly to determine the primary evapotranspiration (ET) coefficient, as radiation interception and evaporative surface area are directly related to canopy cover. Crop size and development with time depends on water supply; therefore, crop canopy maps are tools for the detection of the spatial uniformity of irrigation systems. Several aerial scan campaigns were deployed in the Upper Galilee of Israel in the 2017 and 2018 growing seasons to follow up and evaluate the irrigation uniformity and crop coefficients of peanuts and cotton by RGB scans of a Phantom 4 multirotor unmanned aerial vehicle (UAV) and DJI Mavic-Pro UAV equipped with RGB and near-infrared (NIR) sensors. Foliage intensity and coverage were enhanced by a green-red vegetation index (GRVI), which is a normalized difference vegetation index (NDVI)-like process where the green channel replaced the NIR. The results demonstrated that the GRVI is suitable for the purpose of determining the vegetation cover. Furthermore, the GRVI yielded better results than the NDVI in recognizing phenological crop changes (especially senescence) and in detecting heterogeneity in field irrigation. Therefore, this research proves the applicability of a low-cost digital camera mounted on an easily accessible UAV for crop cover and actual, in-field, ET coefficients determination and irrigation uniformity evaluation.

A SIMPLE crop model

Abstract Crop models are important tools for assessing the impact of climate change on crop production. While multiple models have been developed over the past decades for the major food and fiber crops such as wheat, maize, soybean, rice, and cotton, there are few or none for many other crops. The goal of this study was to develop a simple generic crop model (SIMPLE) that could be easily modified for any crop to simulate development, crop growth and yield. The crop model SIMPLE includes 13 parameters to specify a crop type, with four of these for cultivar characteristics. Commonly available inputs that are required for the crop model SIMPLE include daily weather data, crop management, and soil water holding parameters. The initial SIMPLE model was calibrated and evaluated for 14 different annual crops using observations for biomass growth, solar radiation interception, and yield from 25 detailed field experiments for a total of 70 treatments from 17 sites, resulting in a RRMSE of 25.4% for final yield. A sensitivity analysis comparing a C3, C4 and a legume crop showed an expected response to a gradual increase in temperature and atmospheric CO2 concentrations. A regional gridded simulation for US potatoes reproduced the general observed patterns of spatial yield variability. Because the model is simple, it has several limitations, including the lack of response to vernalization and photoperiod effect on phenology. The model includes water, but no nutrient dynamics. However, an advantage of the model simplicity is that it can be easily adapted and evaluated for any new crop, based on literature data and field experiments, or general crop data such as sowing and harvest dates and yield statistics. The model is available in several simulation frameworks including a stand-alone version in R, Excel and as part of DSSAT.

Efisiensi Penggunaan Radiasi Matahari dan Respon Tanaman Kedelai (Glycine max L.) terhadap Penggunaan Mulsa Reflektif

One of factors affecting the productivity of soybean crop is the availability of solar radiation. Reduction of solar radiation reaching soybean crop by cloud cover especially during rainy season or by shade of trees could potentially decrease soybean production. The availability of radiation for the crop can be increased through the use of reflective mulch to reflect back transmitted radiation to the crop canopy. This study aimed to determine the effect of shade and reflective mulch on crop solar radiation balance and crop productivity responses. A field experiment in Bogor, Indonesia in July 2016 to January 2017, was conducted, applying a Nested Design-two factors model with three replications. The first factor was two levels of shading, i.e., without and with 50% shade; and the second factor was three levels, i.e., without mulch, black silver mulch, and metallic mulch. The results showed that the use of mulch influenced the radiation balance of plants, increasing distribution of radiation reception in plants, solar radiation interception and RUE. The use of mulch caused changes in canopy structure by increase LAI, so that the inhibited radiation was higher. The reflected radiation from the mulch increased production per plants and weight of 1,000 seeds in shaded plants.Keywords: black silver mulch, metallic mulch, radiation balance, radiation interception, shading

Plant development and solar radiation interception of four annual forage plants in response to sowing date in a semi-arid environment

Annual forage crops attract more attention to researchers for it can be used as both forage in animal production and ethanol production in industry. Sowing date are critical to increase crop yield potential in semi-arid environments. Successful establishment and canopy develop are two key aspects ensuring the final yield of forage crop. Therefore, emergence time, leaf appearance and solar radiation interception by the canopy were measured with four annual forage grasses [maize (Zea mays), Sudan grass (Sorghum sudanense Stapf., S), foxtail millet (Setaria italic) and Japanese millet (Echinochloa crus-galli var. frumentacacea)] during the period of 2011–2013 in the western Loess Plateau of China. The results showed that a delay of sowing date could decrease the time for crop emergence. In addition, a decrease in the final leaf number (FLN) and the individual leaf area (ILA) (maize, foxtail millet and Japanese millet) from delayed sowing resulted in less light interception (RI). The variation FLN was closely related to day length (DL) and initial soil water and rainfall at flowering (Ws+Rf) for maize and foxtail millet, thermal time (TT), DL and Ws+Rf for Sudan grass and Japanese millet. Changes in leaf area per plant (LAsingle) in Sudan grass, foxtail millet and Japanese millet were caused by leaf area elongation rate (LAER). Sowing date did not affect leaf appearance rate (LAR) in Japanese millet while decreased in Sudan grass and increased in foxtail millet when the sowing date was delayed, mainly due to changes in DL, TT and Ws+Rf. Variations in individual leaf area (ILA) and LAER indicated the strong plasticity of the four crop species. Therefore, the results of this study improved the understanding of the relationship between sowing date and canopy development and provide important information in crop management and breeding to increase the crop yield.

Effects of afforestation on soil and ambient air temperature in a pair of catchments on the Chinese Loess Plateau

Climate models and satellite remote sensing have been used to determine the effects of afforestation on soil temperature at regional and global scales. However, the coarse spatial resolution of both methods have made them insensitive to local topography, which is a controlling factor of the surface energy budget, especially in areas with complex topography. While typically applied only locally at representative sites, long-term field measurements can shed light on the role of topography on soil temperature after afforestation and provide direct evidence to verify and calibrate the results from modeling and satellite observation. In this study, a pair of neighboring catchments (one afforested and the other with natural regrowth of grasses) on the Chinese Loess Plateau (CLP) was selected to assess the effects of afforestation on soil and ambient air temperature at different slope positions with an entire year of continuous measurements collected every 10 min. The results showed that the uphill slope in both catchments experienced higher soil and air temperatures than the downhill gully, where less solar radiation was received at the ground surface due to canopy interception and topographic shading. For example, the annual average soil (10–100 cm depth) and air temperature in the uphill slope in the forestland catchment was 1.09 and 1.22 °C higher than in the downhill gully, respectively. The effects of topography on soil and air temperature varied at different times of the year, and these effects interacted with the growth status of vegetation. In winter and spring, topography significantly affected soil and air temperature due to varied solar radiation received at different slope positions. By contrast, in summer, the effect of vegetation increased along with higher evapotranspiration and more solar radiation interception by the canopy, especially in the forestland catchment, which showed cooler soils than the other catchment during both the days and nights at all investigated slope positions. However, compared with the grassland catchment, the uphill slope of the forestland catchment had cooler air temperatures during the day, but warmer temperatures at night. We have concluded that both topography and afforestation influence the spatial variation and temporal dynamics of soil and air temperature, and they thereby the surface energy balance of the CLP. More local studies are warranted in order to continue to calibrate regional models and remote sensing data.

Microclimatic conditions in the canopy strata and its relations with the soybean yield.

Despite its economic importance, the microclimate in soybean canopies has not yet been studied in detail. Such a study can yield valuable information regarding the interaction of a crop with its environment. In this context, the aim of this study was to evaluate the solar radiation dynamic and yield responses for each canopy strata for two soybean cultivars with determined and undetermined growth habits. A field study was conducted during the 2013/2014 and 2014/2015 growing seasons in the city of Frederico Westphalen, Rio Grande do Sul, Brazil. The cultivar NA6411, with a determinate growth habit, presented a greater interception of radiation in the middle and lower canopies strata which results in higher soybean yield when compared to the cultivar TEC6029, and thus, can be recommended for cultivation in crop production systems. The contribution of the middle and upper canopy strata to the total yield formation was greater than that observed in the lower canopy strata due to the greater interception of solar radiation by these strata. To increase soybean yields, new studies regarding the microclimatic conditions of the soybean canopy should be developed to improve the maximum potential yield of the new soybean cultivars.

“A Model for Simulating Photosynthesis in Plant Communities” by W.G. Duncan, R.S. Loomis, W.A. Williams, and R. Hanau, Hilgardia (1967) 38:181–205

This article is part of a series of brief commentaries to highlight papers that have resulted in important and distinctly new perspectives in crop science. A criterion for selection of papers is that they must have been published at least 20 yr ago to allow for a long‐range perspective in assessment of the papers. The current article briefly reviews the paper by W.G. Duncan, R.S. Loomis, W.A. Williams, and R. Hanau published in 1967 that provided original concepts about the interception of solar radiation by crop leaf canopies and the estimate of canopy photosynthesis rate based on the intercepted radiation. They developed a geometric description of beam penetration through leaf layers and calculation of canopy CO2 exchange by considering separately leaves in direct‐beam radiation and in the shade.

The effect of nitrogen timing and rate on radiation interception, grain yield and grain quality in autumn sown oats

There is a growing appreciation of the nutritional and health benefits of oats but little recent research has been conducted on the agronomy of oats. Experiments were conducted in Ireland over a two year period (2016–2017) to study the effect of nitrogen (N) timing and rate on radiation interception, yield and quality of autumn sown oats. Two experiments were conducted in each year. In the first experiment, a nitrogen response curve (0, 30, 60, 90, 120, 150 kg N/ha; split-plot factor) was applied at either GS21, GS30, GS32 or GS39 (main-plot factor). In the second experiment, N was applied at GS30 at rates of 0, 30, 60, 90 kg/ha (main-plot factor) and then at GS32 at rates of 0, 30, 60, 90, 120 and 150 kg/ha (split-plot factor). Measurements of radiation interception were made throughout the growing season in addition to flag leaf chlorophyll content and plant height. Grain yield and quality was quantified at harvest. The effect of N timing on radiation interception diminished as N application was delayed but the timing of N supply had no effect on the grain yield in autumn sown oats as long as the crop had received N by GS32. Grain numbers were strongly related to intercepted radiation, particularly in the period immediately before and during anthesis. Radiation interception increased as the overall rate of N application increased but grain yield reached a plateau at 150 kg N/ha. Increases in grain yield after N application were primarily the result of increases in the number of grains per panicle. Splitting N in different ways between GS30 and GS32 had no significant effect on grain yield and grain weight but, for overall N rates of 120 and 150 kg/ha, hectolitre weight increased as the proportion of N applied at GS30 was increased. Grain numbers in oat crops can be optimised by applying N to ensure that radiation interception is maximised in the period prior to and during anthesis.

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

Reduced planting spacing increase radiation use efficiency and biomass for energy in black wattle plantations: Towards sustainable production systems

There is great interest in how plants interactions in different spacings change along spatial gradients in resource availability, biomass and energy production. In this study, we hypothesized that a positive impact of Acacia mearnsii when grown in reduced spacing, leads to a higher biomass and energy yield. The aim of this study was to evaluate how these spacings and their corresponding effects might influence the radiation use efficiency in biomass and potential energy yield in a short-rotation cycle of black wattle (Acacia mearnsii) in southern Brazil. A field experiment was conducted from September 2008 to September 2015 in the city of Frederico Westphalen, Brazil. The forest biomass was determined by destructive method. Also, the calorific value, radiation use efficiency, light extinction coefficient, solar radiation interception, leaf area index, biomass partitioning, carbon storage and potential energy yield were evaluated. Information generated in this study is relevant and provides information for companies interested in electricity generation from wattle biomass and forest producers thereby assisting in the planning of optimal spacing to be used for biomass production for energy. The highest biomass production and radiation use efficiency were obtained in the reduced tree spacing (2.0 × 1.0 m) which results in a higher amount of biomass for energy production. Therefore, the use of reduced tree spacing should be prioritized and recommended for future exploitation of forest energy plantations.

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.

Agroforestry systems and their effects on the dynamics of solar radiation and soybean yield

Agroforestry systems have been highlighted in the agricultural environment as an alternative form of sustainable production to meet the growing demand for food and energy with less environmental impact. Thus, the aim of this study was to evaluate the effect of different forest species on the dynamics of solar radiation and the productive response of soybean grown in agroforestry systems. Two field experiments were carried out in the city of Frederico Westphalen - Rio Grande do Sul, Brazil. In order to reach the aim of this study, the solar radiation transmissivity and the productive performance of soybean were evaluated. Productivity followed the same tendency as solar radiation transmissivity; in an agricultural year, the species with the higher incidence of solar radiation to the understory presented the best yield. The forest species Schizolobium parayba, Peltophorum dubium and Parapiptadenia rigida were used as they present the potential to compose the agroforestry systems; their canopy structure and leaf architecture provide greater availability of solar radiation in the subforest. The interception of solar radiation by the forest component of more than 50% significantly reduces soybean yield in agroforestry systems, requiring silvicultural practices that promote the availability of solar radiation in the understory.

Effects of micro-sprinkling hose irrigation with different hose lengths on soil water distribution, dry matter accumulation, and grain yield of wheat fields

To explore the optimal hose length of micro-sprinkling hose irrigation in wheat fields, a field trial taking JiMai 22 as test material was carried out in two growing seasons (2015-2016 and 2016-2017). Three lengths of micro-sprinkling hoses with 80-mm width were used, including 60 m (T1), 80 m (T2) and 100 m (T3). The length of trial plot was equal to the hose length. The trial plots were divided to different sample sections every 20-m length along the irrigation direction, which were named as A, B, C, D and E sections, respectively, to examine the effects of micro-sprinkling hose irrigations with different hose lengths on soil water distribution, dry matter accumulation and grain yield of wheat fields. The results showed that: 1) After irrigation at the jointing and anthesis stages in the two growing seasons, the relative soil water content in the 0-40 cm soil layer showed T1<T2<T3 in the A section, T1, T2<T3 in the B section, T1>T2, T3 in the C section and T2>T3 in the D section. The CV of relative soil water content in different sections in the same treatment showed T1<T2<T3. 2) Leaf area index and the rate of canopy photosynthesis active radiation interception at 20 d and 30 d after anthesis, and dry matter accumulation amount after anthesis and at the maturity stage had no significant differences in the A or B section among different treatments. Those indices showed T1>T2, T3 in the C section and T2>T3 in the D section. Leaf area index and rate of canopy photosynthesis active radiation interception at 20 d and 30 d after anthesis and dry matter accumulation amount after anthesis showed T1, T2>T3, and dry matter accumulation amount at the maturity stage showed T1> T2>T3. 3) In the two growing seasons, grain yield in the A and B sections had no significant differences among different treatments, and that showed T1>T2, T3 in the C section and T2>T3 in the D section. Grain yield of each treatment showed T1, T2>T3. 4) The grain yield and water use efficiency showed T1> T2>T3, and the irrigation water use efficiency showed T1>T2>T3 among different treatments in the two growing seasons. Considering grain yield and water use efficiency, hose irrigation with micro-sprinkling hose at 80-mm width and 60-m length was optimal treatment for water-saving and high-yield irrigation, and the suboptimal length was 80 m under this condition. The results could provide theoretical basis for water-saving and high-yield irrigation with micro-sprinkling hose in wheat fields in Shandong Province.

The effect of seeding rate on radiation interception, grain yield and grain quality of autumn sown oats

Abstract Oats are attracting increasing interest as a result of their nutritional and health benefits but increasing financial pressures are forcing growers to review all inputs including seed costs. High seeding rates are traditionally used for autumn sown oats in Ireland but it may be possible to use lower seed rates with resultant savings if oat plants can compensate for lower plant populations. A series of experiments were conducted in Ireland from 2015 to 2017 to investigate if lower seed rates could be used for autumn sown oats without compromising yield or quality. Experiments were conducted on both light and heavy soils at sites near Carlow in the centre of Ireland in which three oat varieties (Barra, Husky and Vodka) were grown at five seeding rates (100, 200, 300, 400 and 500 seeds/m2). Experiments were also conducted at Kildalton in the south east of Ireland in which the same three oat varieties were grown at five different seeding rates (125, 250, 375, 500 and 625 seeds/m2). Establishment decreased significantly with seeding rate. Oat plants at low plant populations developed additional grains primarily through an increase in the number of grains per panicle. At GS32, there was no significant difference in radiation interception between seeding rates from 200 seeds/m2 to 500 seeds/m2. The difference in yield between the lowest and highest seeding rate treatments was 1.1 t/ha at the Carlow sites and 0.7 t/ha at the Kildalton site. There were no significant difference in margin between seeding rate treatments at a grain price of €125/tonne. Grain quality was not affected by seeding rate. Autumn sown oats can compensate for low plant populations with the result that the seeding rates used in good sowing conditions can be reduced without any impact on margin or on grain quality.