Solar Radiation Flux Provides a Method of Quantifying Weed-Crop Balance in Present and Future Climates

A systematic approach to quantifying the weed–crop balance through the flux of solar radiation was developed and tested on commercial fields in a long-established Atlantic zone cropland. Measuring and modelling solar energy flux in crop stands has become standard practice in analysis and comparison of crop growth and yield across regions, species and years. In a similar manner, the partitioning of incoming radiation between crops and the in-field plant community may provide ‘common currencies’ through which to quantify positive and negative effects of weeds in relation to global change. Here, possibilities were explored for converting simple ground-cover measures in commercial fields of winter and spring oilseed rape in eastern Scotland, UK to metrics of solar flux. Solar radiation intercepted by the crops ranged with season and sowing delay from 129 to 1975 MJ m−2 (15-fold). Radiation transmitted through the crop, together with local weed management, resulted in a 70-fold range of weed intercepted radiation (14.2 to 963 MJ m−2), which in turn explained 93% of the corresponding between-site variation in weed dry mass (6.36 to 459 g m−2). Transmitted radiation explained almost 90% of the variation in number of weed species per field (12 to 40). The conversion of intercepted radiation to weed dry matter was far less variable at a mean of 0.74 g MJ−1 at both winter and spring sites. The primary cause of variation was an interaction between the temperature at sowing and the annual wave of incoming solar radiation. The high degree of explanatory power in solar flux indicates its potential use as an initial predictor and subsequent monitoring tool in the face of future change in climate and cropping intensity.

A Review of Evapotranspiration Measurement Models, Techniques and Methods for Open and Closed Agricultural Field Applications

Detailed knowledge of energy and mass fluxes between land and the atmosphere are necessary to monitor the climate of the land and effectively exploit it in growing agricultural commodities. One of the important surface land fluxes is evapotranspiration, which combines the process of evaporation from the soil and that of transpiration from plants, describing the movement of water vapour from the land to the atmosphere. Accurately estimating evapotranspiration in agricultural systems is of high importance for efficient use of water resources and precise irrigation scheduling operations that will lead to improved water use efficiency. This paper reviews the major mechanistic and empirical models for estimating evapotranspiration including the Penman–Monteith, Stanghellini, Priestly–Taylor, and Hargreaves and Samani models. Moreover, the major differences between the models and their underlined assumptions are discussed. The application of these models is also reviewed for both open and closed field mediums and limitations of each model are highlighted. The main parameters affecting evapotranspiration rates in greenhouse settings including aerodynamic resistance, stomatal resistance and intercepted radiation are thoroughly discussed for accurate measurement and consideration in evapotranspiration models. Moreover, this review discusses direct evapotranspiration measurements systems such as eddy covariance and gas exchange systems. Other direct measurements appertaining to specific parameters such as leaf area index and surface leaf temperature and indirect measurements such as remote sensing are also presented, which can be integrated into evapotranspiration models for adaptation depending on climate and physiological characteristics of the growing medium. This review offers important directions for the estimation of evapotranspiration rates depending on the agricultural setting and the available climatological and physiological data, in addition to experimentally based adaptation processes for ET models. It also discusses how accurate evapotranspiration measurements can optimise the energy, water and food nexus.

Impact of integrated nutrient management on production potential of mungbean

Mungbean is one of the important grain legume crops in Pakistan due to its vigorous growth even in adverse environment. Mungbean is part of daily cuisine in the country but its production is low mostly due to imbalance fertilization. The study was carried out to find best combination of nitrogen (N), phosphorus (P) and potassium (K) for maximum production under less fertile soils during 2017-2018. In this study, three combinations of NPK (i.e., 30:30:0, 30:60:0 and 30:60:30 kg ha-1 ) were compared with control (without fertilization). Maximum pods per plant (22.43), pod length (9.51 cm), seeds per pod (8.97), 1000 seed weight (44.07 g), seed yield (1163 kg ha-1 ), biological yield (5231 kg ha-1 ) and harvest index (24.63 %) were obtained from 30:60:30 kg NPK ha-1 during 2017 and similar trends were found during 2018. Maximum leaf area duration (212.64, 215.09 days), crop growth rate (3.99, 4.02 g m-2 d -1 ), net assimilation rate (2.46, 2.54 g m-2 d -1 ) and fraction of intercepted radiation (0.89, 0.88 MJ m-2 ) were obtained from mungbean plant under 30:60:30 kg ha-1 NPK application during 2017 and 2018, respectively. These results are suggesting that integrated application of nitrogen, phosphorous and potash is very imperative to attain higher production of mungbean under semi-arid environments. It is concluded from the findings that farmers can harvest maximum final outputs of mungbean by the application of 30:60:30 kg ha-1 NPK, respectively.

Radiation Dynamics on Crop Productivity in Different Cropping Systems

Global demand for food has always been on the increase due to the increase of the population in this world. Intercropping is one of the alternatives of agronomic practices that is widely practiced in ensuring food security and enhancing yield stability. Strip, mixed, and relay intercropping can be practiced to increase crop production. In addition to achieving a successful intercropping system, factors such as suitable crops, time of sowing, maturity of the crop, and plant density need to be considered before and during planting. Besides, practiced intercropping becomes a useful cropping system to increase efficient resource utilization, enhance biodiversity, promote soil health, enhance soil fertility, erosion control, yield advantage, weed, pest, and disease control, insurance against crop failure, ecosystem and modification of microclimate, market instability, and increase farmers income. Crop productivity in any types of cropping system implemented relies primarily on the interception of photosynthetically active radiation (PAR) of crop canopy and conversion of intercepted radiation into biomass or known as radiation use efficiency (RUE). Both PAR and RUE are important measurements that have significant roles in crop growth and development in which the accessibility of these radiation dynamics is connected with the leaf area index and crop canopy characteristics in maximizing yield as well as total productivity of the crop component in intercropping systems.

Productive Performance of Alfalfa (Medicago sativa L.) at Different Age of Resprout in the Spring Season

Objective: To determine the growth and productive performance curves, to obtain the optimal cutting moment in alfalfa, depending on the age of resprouting, in the Spring season.Design/Methodology/Approach: The treatments were cuts at different age of the plant and the variables evaluated: Dry Matter Yield (DMY) Botanical and Morphological composition (BMC), Plant Height (PH), Leaf/Stem Ratio (L/SR), and Intercepted Radiation (IR). The stastical analysis was with the PROC GLM procedure, of the SAS software, and the adjustedcurves were obtained with the Curve Expert Professional 2.0 software.Results: There was an increase in the DMY, leaf, stem, PH, and IR, as the resprouting age advanced, but not, the L/SR which had an inverse behavior. The maximum DMY was obtained (4,768 kg DM ha-1) in week seven. There was a greater amount of leaf with average 52%, followed by the stem (36%), weeds (7%), detritus (4%) and inflorescence (1%). The PH washigher in week seven with 53 cm. Likewise, the highest IR in week tree with 86%. However, the L/SR was higher in week one with 2.4. The IR and L/SR presented the lowest R2 (0.90 and 0.93, respectively). In contrast, DMY and PH presented apositive relationship (R2 of 0.98 and 0.97, respectively).Study Limitations/Implications: There were no limitationsFindings/Conclusions: The productive performance of Premium variety alfalfa was variable depending on the resprouting age, in which the botanical and morphological characteristics changed, with better characteristics in the fifth week

Parameter Sensitivity and Uncertainty of Radiation Interception Models for Intercropping System

Estimating the interception of radiation is the first and crucial step for the prediction of production for intercropping systems. Determining the relative importance of radiation interception models to the specific outputs could assist in developing suitable model structures, which fit to the theory of light interception and promote model improvements. Assuming an intercropping system with a taller and a shorter crop, a variance-based global sensitivity analysis (EFAST) was applied to three radiation interception models (M1, M2 and M3). The sensitivity indices including main (Si) and total effects (STi) of the fraction of intercepted radiation by the taller (ftaller), the shorter (fshorter) and both intercrops together (fall) were quantified with different perturbations of the geometric arrangement of the crops (10-60 %). We found both ftaller and fshorter in M1 are most sensitive to the leaf area index of the taller crop (LAItaller). In M2, based on the main effects, the leaf area index of the shorter crop (LAIshorter) replaces LAItaller and becomes the most sensitive parameter for fshorter when the perturbations of widths of taller and shorter crops (Wtaller and Wshorter) become 40 % and larger. Furthermore, in M3, ftaller is most sensitive to LAItaller while fshorter is most sensitive to LAIshorter before the perturbations of geometry parameters becoming larger than 50 %. Meanwhile, LAItaller, LAIshorter, and Ktaller are the three most sensitive parameters for fall in all three models. From the results we conclude that M3 is the most plausible radiation interception model among the three models.

Radiation Interception, Conversion and Partitioning Efficiency in Potato Landraces: How Far Are We from the Optimum?

Crop efficiencies associated with intercepted radiation, conversion into biomass and allocation to edible organs are essential for yield improvement strategies that would enhance genetic properties to maximize carbon gain without increasing crop inputs. The production of 20 potato landraces—never studied before—was analyzed for radiation interception ( ε i ), conversion ( ε c ) and partitioning ( ε p ) efficiencies. Additionally, other physiological traits related to senescence delay (normalized difference vegetation index (NDVI) s l p ), tuberization precocity ( t u ), photosynthetic performance and dry tuber yield per plant (TY) were also assessed. Vegetation reflectance was remotely acquired and the efficiencies estimated through a process-based model parameterized by a time-series of airborne imageries. The combination of ε i and ε c , closely associated with an early tuber maturity and a NDVI s l p explained 39% of the variability grouping the most productive genotypes. TY was closely correlated to senescence delay (r P e a r s o n = 0.74), indicating the usefulness of remote sensing methods for potato yield diversity characterization. About 89% of TY was explained by the first three principal components, associated mainly to t u , ε c and ε i , respectively. When comparing potato with other major crops, its ε p is very close to the theoretical maximum. These findings suggest that there is room for improving ε i and ε c to enhance potato production.