Radiation Interception Research Articles

The influence of spring grazing management on yield and water use of rainfed lucerne

Flexible spring grazing management can increase the use of lucerne on farms. However, the negative impacts of set stocking on the survival of plants usually preclude its use. In this experiment, crops of ‘Stamina 5’ lucerne at Ashley Dene, Lincoln University were rotationally grazed, semi-set stocked or set stocked from September to December 2011. Dry matter (DM) yield to December was 6.3 t DM/ha, and consistent among crops. However, the larger leaf area of the semi-set- and set-stocked crops intercepted 45% more solar radiation and transpired 25% more water than the rotationally grazed crop. The set-stocked regime had a lower efficiency of resource use. This was probably due to greater respiration and/or partitioning of DM to the root mass. Set-stock regimes required continual initiation of new shoots from basal buds, which remobilised and, therefore depleted, stored assimilates. To minimise this impact, farmers should maintain a canopy cover of 2 to 2.5 t DM/ha (~20 cm tall) on any set-stocked lucerne. This will maximise radiation interception and compensate for reserve losses. In the study year, grazing management did not influence feed supply through the manipulation of water use because soil evaporation losses were inversely related to crop water use. Consequently, total water use was consistent among crops, with higher soil evaporation from frequent rewetting of the soil for rotationally grazed crops. For farmers, these results suggest continuous grazing of lucerne is possible, but it should be managed to maintain full canopy cover and minimise reserve depletion that will reduce DM yields and stand persistence.

Intensifying of reflected radiation under oil palm canopy and its effect on growth and production of soybean

The main problem of cultivating soybeans under the stands of oil palm plantations in the low intensity of solar radiation. The aim of this study was to analyze the effect of reflective mulch application on the growth, physiology, and production of soybeans cultivated as intercropping under oil palm plantation stands. The study was carried out at Cimarga Banten Indonesia using a two-factor randomized nested design with three replications. The treatments consist of two factors, viz different age of oil palm stands and types of reflected mulches. The use of reflective mulch would increasing albedo, as well as in intensifying reflected radiation of land surface by 29% for organic mulch and by 49% for inorganic mulch. The application of organic and inorganic reflective mulches could increase the interception of solar radiation by soybean plants and had positive effects on height, stem diameter, leaf area index, biomass, and radiation use efficiency. The use of organic reflective mulch increased the amount of relative leaf chlorophyll in shaded conditions and the amount of chlorophyll in the upper, middle and lower position leaves. Organic and inorganic reflective mulches had a significant effect on increasing the number of fill pods, production, and weight of 100 soybean grains.

Impact of rice straw biochar and irrigation on maize yield, intercepted radiation and water productivity in a tropical sandy clay loam

Continuous cultivation of staple crops to feed a growing population in the semi-deciduous agro-ecological zone of eastern Ghana (SDAG) has led to degraded soils and decreased crop yields. Biochar constitutes a potential remedy as it is often reported to improve soil health and increase crop yield of infertile soils. We thus conducted an experiment over two seasons to evaluate the impact of rice straw biochar on yield, radiation interception and water productivity of maize grown in the SDAG. The biochar was incorporated into the soil at rates of 0, 15 and 30 t ha−1 under irrigated and non-irrigated conditions. Maize grain yield (GY), accumulated intercepted photosynthetic active radiation (IPAR) and water productivity (WP) were compared among treatments. Regardless of season, the highest GY, IPAR and WP were achieved in plots amended with 30 t ha−1 biochar. A biochar rate of 30 t ha−1 increased grain yield by 17% and 36% and IPAR by 19% and 25% in 2017 and 2018 seasons, respectively, compared to a no biochar control. For both seasons, maize GY for the 15 t ha−1 treatment was statistically similar to that of 0 t ha−1 treatment whether irrigated or not. Irrigation increased grain yield by 9% and IPAR by 3% in 2017 and with 30% and 17%, respectively, in the dryer 2018 season. The effects of biochar and irrigation were additive. Water productivity from the 30 t ha−1 treatment was significantly higher in the non-irrigated than in the irrigated plots. Overall, in the SDAG, a biochar soil amendment rate of 30 t ha−1 might be a viable solution for farmers to increase yield and enhance water productivity of maize. Future studies should focus on the effect of biochar on the soil and crops over a longer time span in order to recommend viable management options to the farmers in SDAG.

Conservation agriculture had a strong impact on the sub-surface soil strength and root growth in wheat after a 7-year transition period

The study compared conservation agriculture (CA) practice (no-tillage, crop residue cover on the surface and relay mung bean) with conventional intensive tillage system, in order to evaluate their effects on soil strength and water content, total porosity and pore-size distribution, roots and above-ground plant growth in wheat under a rice-wheat rotation. The experiment was started in the kharif season of the year 2010 in the research farm of the Indian Agricultural Research Institute, New Delhi, India. Observations were taken during 6th, 7th and 8th year of the rotation. The CA practice primarily reduced the sub-surface (15–30 and 30–45 cm) soil strength by 20–25% owing to 14% higher water content at this layer, and increased the total porosity (17%) and retention pores (22%). Soil aggregation and organic C improved primarily in the surface layer (0–15 cm). The modified soil physical properties led to better root growth, plant leaf area index and solar radiation interception, and higher grain and straw yields. The CA practice significantly contributed to improving the soil physical condition, especially in reducing the sub-surface compaction and improvement on root growth in wheat. This is significant in our quest to increase and sustain the rice-wheat production system in the Indian subcontinent.

Differential cooling effects of landscape parameters in humid-subtropical urban parks

Thermally comfortable urban parks can attract more visitors and promote the delivery of health benefits to citizens. High tree cover (TREE) and low sky view factor (SVF) are known to reduce air temperature and improve thermal comfort. However, the temperature effects of other landscape parameters are less clear, such as building volume ratio (BV), distance from sea (SEA), park area (AREA), pavement cover (PAVEMENT), road cover (ROAD), shrub cover (SHRUB), turf cover (TURF) and water body (WATER). This study aimed to identify landscape parameters that were significantly associated with air temperature in urban parks and estimate their cooling potentials through empirical models. One hundred precision sensors were installed in 14 urban parks in Hong Kong in summer 2018 to collect air temperature data. ROAD, SEA, TREE and SHRUB had the strongest impacts on temperatures. Considering a circular area with a 20-m radius, a 50% decrease in ROAD, 50% increase in TREE and SHRUB could reduce daytime mean air temperature by 0.3, 0.4 and 0.2 °C respectively. The same landscape changes would reduce nighttime mean air temperature by viz. 0.3, 0.2 and 0.2 °C. Compared to an inner-city park (500 m from sea), the empirical model suggested that daytime and nighttime mean air temperature in a waterfront park (10 m from sea) is expected to be 0.4 and 0.2 °C lower respectively. Urban parks should be sufficiently large to buffer the warming effect of roads. Very high tree cover (>90%) is recommended for an effective interception of solar radiation.

Sensor Scheduling Based on Risk for Target Tracking

A sensor scheduling approach focusing on managing the operational risk in target tracking is proposed. The scheme selects sensor actions so that the operational risks are the minimum. First, given the definition, existence of risk in sensor scheduling is analyzed. Second, the target missing risk and the sensor radiation interception risk are summed to create the sensor scheduling objective functions, including myopic sensor scheduling and non-myopic sensor scheduling. Furthermore, to obtain sensor management schemes according to the objective functions, the improved bee colony algorithm based on double-roulette and in combination with the particle swarm optimization algorithm is proposed. Finally, simulations are carried out to illustrate the models and algorithms in the paper possess some advantages over existing ones, including being more practical, keeping nearly the same or even better tracking performance with lower risk values, and owing better sensor scheduling solutions.

Intercropping Optimizes Soil Temperature and Increases Crop Water Productivity and Radiation Use Efficiency of Rainfed Potato

Integrating crop species with different photosynthetic pathways has great potential to increase efficiency in the use of scarce resources. In order to tap the resource complementarity emanating from this mix, this study intercropped potato (Solanum tuberosum L.) with lima bean (Phaseolus lunatas L.) and dolichos (Lablab purpureous L.), and related soil temperature with radiation use efficiency and crop water productivity of rainfed potato in the upper midland (1552 m above sea level (masl), lower-highland (1854 masl) and upper-highland (2553 masl)) agro-ecological zones of Kenya. Leaf area index (LAI), light interception, soil temperature and soil water contents (SWC) were quantified at different stages of potato growth and related with the radiation use efficiency (RUE) and crop water productivity (CWP) of potato. Intercropping increased crop LAI by 26–57% relative to sole potato stands and significantly lowered the soil temperatures in the 0–30 cm depth by up to 7.3 °C. This caused an increase in SWC by up to 38%, thus increasing RUE by 56–78% and CWP by 45–67%. Intercropping potato with legumes is coupled with optimum root-zone soil temperature and soil water content, thus potentially exerting additive relations in radiation interception and subsequent conversion into crop biomass.

Response of photosynthetic active radiation interception, dry matter accumulation, and grain yield to tillage in two winter wheat genotypes

ABSTRACT To examine the effects of winter wheat genotypes on dry matter (DM) accumulation and grain yield (GY) under no-tillage conditions in North China Plain (NCP), a field experiment was conducted using the genotypes Tainong 18 (F) and Jimai 22 (J). Two tillage systems were tested, conventional tillage (CT) and no-tillage (NT) during the 2015/2016 and 2016/2017 winter wheat growing seasons. Genotypes and tillage systems were compared regarding DM accumulation, GY, leaf area index (LAI), photosynthetic active radiation (PAR) interception, and flag leaf fluorescence parameters. LAI, PAR interceptions, and flag leaf fluorescence parameters were significantly higher under CT than under NT conditions. This suggests that the efficiency of light harvesting by the PSII reaction center of leaves can increase due to CT. DM accumulation was significantly higher under CT than under NT. Spike DM accumulation was higher in F than in J in the heading and the filling stages. In both growing seasons, GY was significantly higher under CT than under NT, GY of NTF was significantly higher than that of NTJ, which was due to a significantly higher number of kernels per spike. This indicates that genotype F can compensate for a low GY due to NT.

Effects of directional planting on light environment and leaf photosynthesis of summer maize population

To improve light environment, photosynthetic capacity, and thus the yield of maize, the effects of directional planting on light distribution in canopy and photosynthetic characteristics of ear leaves, as well as the performance of PSII that closely related with photosynthetic characteristics and reflected by the rapid chlorophyll fluorescence kinetic curves were examined in Zhengdan 958 maize variety. The results showed that the orientation of leaves remarkably affected photosynthetically active radiation (PAR) interception of ear leaves, with PAR interception of ear leaves in southward treatment being 271.8% higher than that under northward treatment. The orientation of leaves affec-ted photosynthetic light use efficiency of ear leaves under high and low light conditions. The southward treatment increased net photosynthetic rate (Pn) under saturated light in ear leaves, indicating that the use efficiency to high light was enhanced in leaves of southward treatment. In contrast, the northward treatment increased the apparent quantum yield (α) of ear leaves, indicating leaves in southward treatment adapted the light-limited environment. During the early stage after anthesis, the performance of PSII electron donor side and electron acceptor side was significantly improved, and thus enhanced the performance of PSII reaction center (PIABS) and fluorescence photochemical quenching coefficient (Ψo) in ear leaves of southward treatment. The increase of quantum yield of electron transfer (φEo) indicated the enhancement of transfer performance of electrons from photosystem 2 (PSII) to photosystem 1 (PSI) in leaves of southward treatment. The photosynthetic performance of ear leaves showed a trend of southward > eastward > westward > northward during the early stage after anthesis. Forty days after anthesis, the use efficiency to high light decreased in ear leaves of southward treatment, but the ear leaves of southward treatment showed high use efficiency to low light, which changed the trend of photosynthetic performance of ear leaves to northward > westward > eastward > southward. In summary, northward and eastward treatments improved the light distribution in canopy, the PAR interception of ear leaves, the capacity of photosynthesis and dry matter production, and consequently increased the yield of summer maize.

Automatic drip irrigation scheduling effects on yield and water productivity of banana

Water scarcity is one of the major factors affecting the productivity of banana. Drip irrigation (DI) has been found as a water saving technique in banana cultivation. Further, sensor-based automated DI which has been considered as a smart and real time water application technique might increase the water savings and enhance yield of banana. With this hypothesis, a field experiment was conducted to study the performance of automated DI in banana (cv. Grand Naine) at Bhubaneswar, India during 2016–2017. Five automated DI schedules: (i) soil water sensor-based irrigation (I1) and timer based irrigation (ii) at 1 h interval 3 times daily at 80% crop evapotranspiration (ETc) (I2), (iii) at 2 h interval 2 times daily at 80% ETc (I3), (iv) at 1 h interval 3 times daily at 60% ETc (I4) and (v) at 2 h interval 2 times daily at 60% ETc (I5) were compared with manually operated DI at 100% ETc (I6) in the crop. The highest vegetative growth of plants (plant height, canopy diameter, stem girth) was observed with manually operated DI. However, sensor-based DI produced 15% higher fruit yield with 20% water saving, resulting in 40% higher water productivity (yield per unit quantity of water) compared with manually operated DI (water used, 820 mm; yield, 60.5 t ha−1; water productivity, 6.2 kg m−3) in the crop. The fruit qualities (total soluble solids and acidity) of sensor-based irrigated plants were superior to manually irrigated plants. The volumetric soil water content under manual DI was marginally higher (11–15%) than that under sensor-based DI (21.2–24.8%). The soil available nutrients (N, P and K) and leaf nutrients content of the plants followed the similar trend of soil water content under different treatments. The yield forecasting based on leaf-N, leaf-K, leaf water content and radiation interception using ‘Principal component analysis’ performed well with reasonably accuracy (R2 = 0.82). Overall, these results reveal that soil water sensor-based automated DI is a productive and water saving technique which may be adopted in banana cultivation in eastern India and anywhere else with similar agro-climates of the study site.

Structures and Mechanisms of 20–60-Day Intraseasonal Oscillation of the Observed Rainfall in Vietnam

Abstract The present study explores the characteristics of the 20–60-day intraseasonal oscillation (ISO) in the 29-yr observed rainfall in north Vietnam (NVN), central Vietnam (CVN), and south Vietnam (SVN) in rainy seasons. Composite analyses reveal that the 20–60-day ISO in NVN accompanies dual vortices straddling Taiwan, which alternately favor and suppress convection extending from the northern Philippines to NVN. The wet phase in CVN coincides with convergence of northerly and easterly winds over the region. The large-scale pattern governing the 20–60-day ISO in SVN resembles the characteristics of the boreal summer ISO (BSISO). Conditionally unstable anomalies are observed within anomalous anticyclones where the moisture flux diverges out during the dry phase in NVN and SVN, and vice versa. Such anomalies prevent the existence of the anticyclones and finally replace them with anomalous cyclones to start the wet phase. The unstable anomalies could result from descending motion that increases the boundary layer temperature due to adiabatic compression of air. Conversely, boundary layer cooling due to evaporation of rain and interception of solar radiation by clouds produces stable anomalies. The unstable anomalies, moisture flux convergence, and vertical motions shift northward from the convection maximum, leading to the northward propagation of the BSISO convection. The 20–60-day ISO in CVN is not governed by local instability. Vertical cross sections indicate that the ISO in SVN possesses a westward-tilting structure, which is not observed in the NVN and CVN case.

Intercropping Simulation Using the SWAP Model: Development of a 2×1D Algorithm

Intercropping is a common cultivation system in sustainable agriculture, allowing crop diversity and better soil surface exploitation. Simulation of intercropped plants with integrated soil–plant–atmosphere models is a challenging procedure due to the requirement of a second spatial dimension for calculating the soil water lateral flux. Evaluations of more straightforward approaches for intercrop modeling are, therefore, mandatory. An adaptation of the 1D model Soil, Water, Atmosphere and Plant coupled to the World Food Studies (SWAP/WOFOST) to simulate intercropping (SWAP 2×1D) based on solar radiation and water partitioning between plant strips was developed and the outcomes are presented. An application of SWAP 2×1D to maize–soybean (MS) strip intercropping was evaluated against the monocropping maize (M) and soybean (S) simulated with the 1D model SWAP/WOFOST, and a sensitivity analysis of SWAP 2×1D was carried out for the intercropping MS. SWAP 2×1D was able to simulate the radiation interception by both crops in the intercropping MS and also to determine the effect of the radiation attenuation by maize on soybean plants. Intercropped plants presented higher transpiration and resulted in lower soil evaporation when compared to their equivalent monocropping cultivation. A numerical issue involving model instability caused by the simulated lateral water flux in the soil from one strip to the other was solved. The most sensitive plant parameters were those related to the taller plant strips in the intercropping, and soil retention curve parameters were overall all significantly sensitive for the water balance simulation. This implementation of the SWAP model presents an opportunity to simulate strip intercropping with a limited number of parameters, including the partitioning of radiation by a well-validated radiation sharing model and of soil water by simulating the lateral soil water fluxes between strips in the 2×1D environment.

Modeling evapotranspiration and its components of maize for seed production in an arid region of northwest China using a dual crop coefficient and multisource models

Accurately modeling evapotranspiration (ET) and its components of maize grown for seed production is essential for precision irrigation management. In this study, a dual crop coefficient method and a multisource model based on radiation interception by adjacent crop varieties were used to estimate ET and its components in the arid region of northwest China. The dual crop coefficient method and multisource model were validated using observed ET (ETEC), transpiration (T) of female (Tsf) and male (Tsm) parents and evaporation (Es). Observations were made using the eddy covariance system, sap flow measurements, and micro-lysimeter in 2013 and 2014. Results showed that ET estimated by the dual crop coefficient method was close to ETEC at the midseason stage, and was higher than ETEC both at the initial and the development stage due to the constant value of initial basic crop coefficient and linear interpolation at the development stage. The estimated T of female and male parents was greater than Tsf and Tsm in both years. Soil evaporation estimated by the dual crop coefficient method was greater than measured soil evaporation in the late growth stage. While the ET, T of female and male parents and E predicted by the multisource model were closer to the measurements. Estimated ET was 2% less (2013) and 4% greater (2014) than ETEC, T of male parents was 8% and 3% less than Tsm, T of female plants was 8% and 6% less than Tsm, and E was 6% and 3% less than Es. Thus the multisource model based on radiation interception by neighboring species is suitable for estimating ET and its components of maize grown for seed production in the arid region of northwest China.

Risk-based sensor scheduling for target detection

A risk-based sensor scheduling method is proposed and applied to target detection in this paper. This paper mainly focuses on the sensor radiation interception risk and target detection risk. Firstly, the general risk-based sensor scheduling model is established; Secondly, the target detection risk model and sensor radiation risk model are proposed respectively. It is stressed that the radiation interception model is based on Partially Observed Markov Decision Process (POMDP) due to the reason that parameters of the enemy's radiation receiver are not accessible to calculate the radiation interception risk directly; Furthermore, combined with double-roulette, the basic artificial bee colony (ABC) is improved to get sensor scheduling schemes from the objective function; Ultimately, simulations are conducted and indicate that the models and the algorithm in the paper possess some advantages over existing ones.

Effectiveness of conservation agriculture in increasing crop productivity in low-input rainfed rice cropping systems under humid subtropical climate

Since the early 2000s conservation agriculture (CA) has been promoted in the Lake Alaotra region of Madagascar for a more sustainable and profitable agriculture. There is, however, little known about its performance in low-input rainfed rice-based cropping systems. We conducted a study during two growing seasons (2013/14 and 2014/15) on an experiment that was established in 2009 at the agricultural research station of the National Center for Applied Research and Rural Development (FOFIFA) in the Lake Alaotra region of Madagascar. The experimental setup was a randomized block design with four replications. Two soil/residue management treatments were studied, conventional tillage without residue retention (CT) and no-tillage with residue retention (NT). These two treatments were tested for a 2-year rotation of maize + Dolichos lablab followed by rice (MD//R) and a 3-year rotation of maize + Stylosanthes guianensis, followed by S. guianensis in the second year, and rice in the third year (MS//S//R). During the 2013/14 and 2014/15 seasons, two levels of weed pressure: ‘high’ and ‘low’ were introduced as a split-plot design on the rice plots. The main determining factors of rice yield in the study region were studied: radiation interception, weed infestation, soil moisture and soil mineral nitrogen (N). Our results showed that five to six years of continuous practice of NT with retention of high amounts of crop residues (more than 5 Mg DM ha−1) on the soil surface had a significant (p = 0.02) positive effect on rice yield, irrespective of the level of weed pressure and type of crop rotation. CA systems significantly (p < 0.05) reduced weed density and biomass as compared to CT particularly during the vegetative stage of the rice crop in the two growing seasons, which to a certain extent explained the yield gains under CA. In contrast, treatment effects on soil moisture and mineral N contents were marginal. The positive effects of CA on reduced weed pressure may constitute an important benefit for smallholder farmers, who face labour constraints with hand weeding, and usually cannot afford herbicides for weed control.

Transmitted light as a tool to monitor tree leaf phenology and development applied to Quercus petraea

Better knowledge and a more complete long-term monitoring of tree species phenology and tree foliage development are crucial to accurately estimating the impact of climate change on forest ecosystems functioning and on forest species distribution. We set up global solar radiation sensors under the forest canopy and continuously recorded solar radiation in order to follow the development of sessile oak (Quercus petraea L.) foliage in pure stands over four consecutive years and for two levels of stand density. At the same time, we made phenological observations to determine bud burst date. One of our goals was to link observed bud burst dates and transmittance measurements. Our results show that solar radiation transmittance during the leaf unfolding period followed a sigmoid-shaped curve; and that it was possible to fit a generalized logistic model to determine a set of parameters characterizing tree foliage and its development during the unfolding period. Among these parameters, we suggest that the date at which solar radiation interception by foliage reaches 50% could be used to monitor the beginning of the growing season over the long term. The relationship between observed bud burst date and the transmittance model parameters was more complex than we expected. We tested several indices to deduce the date of bud burst from transmittance. We showed that when radiation interception due to foliage reached 10%, this indicated the observed bud burst date. Finally, a linear model including parameters from the generalized logistic models of transmittance as predictors explained 57% of the variability in bud burst date. Complementary research combining light measurements and phenological observations over a longer period of time is needed to know whether these relationships could help estimate bud burst date regardless of the year or the stand density.

Evaluating the potential of winter beet in northern Germany by a simulation model

Abstract Autumn-sown sugar beets may achieve a faster canopy closure in spring compared to spring-sown sugar beets, thus increasing radiation interception and yield. However, to date yield benefits of autumn-sown beets cannot be quantified, as they start to bolt in spring. Therefore, simulation models for winter beet need to be developed. From 2009 to 2012, field trials in northern Germany were carried out with sugar beets sown in spring (conventional sugar beet) as well as sown in autumn (bolting winter beet). Based on these data, a dynamic simulation model was developed and calibrated for winter beets. The model is based on light use efficiency (LUE) approach and considered winter beet-specific aspects like leaf (area) losses due to frost, vernalisation and bolting. For conventional sugar beets, the validation revealed a RMSE of 164 g m-2 and a model efficiency (EF) of 0.93 for root dry matter. For the total dry matter (DMtot) of bolting winter beets, the validation showed a RMSE of 216 g m-2 and an EF of 0.69. Implemented assumptions regarding the non-bolting winter beets allow the model to simulate this beet type as well. A simulation over 12 years (1998-2010) for the site Hohenschulen estimated 1921 g DMtot m-2, 971 g DMtot m-2 and 2474 g DMtot m-2 for conventional sugar beets, bolting winter beets and non-bolting winter beets, respectively. Our results suggest that developing non-bolting winter beets seems be a promising approach to increase beet yields.

Genetic and environmental dissection of biomass accumulation in multi-genotype maize canopies.

Multi-genotype canopies are frequent in phenotyping experiments and are of increasing interest in agriculture. Radiation interception efficiency (RIE) and radiation use efficiency (RUE) have low heritabilities in such canopies. We propose a revised Monteith equation that identifies environmental and genetic components of RIE and RUE. An environmental term, a component of RIE, characterizes the effect of the presence or absence of neighbours on light interception. The ability of a given plant to compete with its neighbours is then identified, which accounts for the genetic variability of RIE of plants having similar leaf areas. This method was used in three experiments in a phenotyping platform with 765 plants of 255 maize hybrids. As expected, the heritability of the environmental term was near zero, whereas that of the competitiveness term increased with phenological stage, resulting in the identification of quantitative trait loci. In the same way, RUE was dissected as an effect of intercepted light and a genetic term. This approach was used for predicting the behaviour of individual genotypes in virtual multi-genotype canopies. A large effect of competitiveness was observed in multi-genotype but not in single-genotype canopies, resulting in a bias for genotype comparisons in breeding fields.

Water use efficiency and light use efficiency in garlic using a remote sensing-based approach

The objective of this paper was to determine the water use efficiency (WUE) and light use efficiency (LUE) values of garlic (Allium sativum L.) and to analyze the normalization of these efficiencies for the atmospheric conditions. We analyzed the use of daily reference evapotranspiration (ETo) and the vapor pressure deficit (VPD) for these purposes. WUE and LUE were valued based on the experimental measurements of dry biomass production and the estimation of transpiration and radiation interception based on time series of Remote Sensing satellite images. The experimental data were obtained in two commercial fields each planted with a different variety of garlic (var. morado and var. spring) growing in different weather conditions in the province of Albacete (in the south-east of Spain). The correlation between the accumulated values of biomass and the estimated values of crop transpiration and radiation absorption resulted in strong linear relationships. The slope of these correlations resulted in values of WUE and LUE, WUE = 5.51 g m−2 mm−1 and LUE = 2.26 g·MJ−1 for both analyzed varieties. The results demonstrated that the inclusion of temperature stress coefficient is required when the WUE and LUE parameters are normalized using the ETo and the VPD variables. However, atmospheric normalization did not conclusively improve results in this study. Results obtained in this paper provided empirical evidence regarding the feasibility of estimating biomass production in garlic based on the same physiological principles used for other crops.

Responses of Canopy Growth and Yield of Potato Cultivars to Weather Dynamics in a Complex Topography: Belg Farming Seasons in the Gamo Highlands, Ethiopia

Potato is an increasingly important crop in Ethiopia. The Gamo Highlands are one of the large potential potato producing regions in Ethiopia. The growing conditions are different from those in the temperate regions, where most of the agronomical expertise on potato has been developed. The influence of environmental conditions on the crop in the Gamo Highlands is poorly understood. We conducted field trials with eight potato cultivars in six locations and during two seasons. The canopy cover (CC) and plant height (PH) were measured with high temporal resolution and tuber yields were assessed as well. The experiments were conducted near our newly installed weather stations at different elevations. CC and PH were strongly correlated with temperature sum (Tsum). Tuber yields differed among elevations and cultivars. Nevertheless, these differences were poorly explained by environmental variables. We also found that no single cultivar performed best at all elevations. The number of branches was a predictor of yield, suggesting that radiation interception was limiting tuber growth. Tuber yield was optimal when the number of days to crop maturity was around 100–110 days. We conclude that Tsum is a predictor of crop growth, but environmental variables poorly explain yield variations, which calls for further investigation.