An Auto-Calibration Tool for the Agricultural Policy Environmental eXtender (APEX) Model

The Agricultural Policy/Environmental eXtender (APEX) model has been widely used to assess changes in agrochemical loadings in response to conservation and management led by US Department of Agriculture (USDA). However, the existing APEX model is limited in quantification of wetland water quality functions. This study improved the current model capacity to represent wetland water quality functions by addition of a new biogeochemical module into the APEX model. The performance of an enhanced APEX model was tested against five observed outgoing water quality variables (e.g., sediment, organic N, NO3, NH4 and PO4) from a wetland within the Eastern Shore of Maryland. Generalized Likelihood Uncertainty Estimation (GLUE) was implemented to assess model uncertainty. The enhanced APEX model demonstrated that it could effectively represent N and P cycling within the study wetland. Although improvement of model performance was limited, the additions of wetland biogeochemical routines to the APEX model improved our understanding of inner mass exchanges within N and P cycling for the study wetland. Overall, the updated APEX model can provide policymakers and managers with improved means for assessment of benefits delivered by wetland conservation.

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Improving Modeling of Quinoa Growth Under Saline Conditions Using the Enhanced Agricultural Policy Environmental eXtender Model

Agronomy ◽

10.3390/agronomy9100592 ◽

2019 ◽

Vol 9 (10) ◽

pp. 592 ◽

Cited By ~ 1

Author(s):

Goehring ◽

Verburg ◽

Saito ◽

Jeong ◽

Meki

Keyword(s):

Soil Salinity ◽

Agricultural Policy ◽

Root Zone ◽

Water System ◽

Salt Uptake ◽

Plant Soil ◽

Stress Functions ◽

Annual Biomass ◽

Increase Productivity ◽

Apex Model

Cultivation of highly salt-tolerant plants (i.e., halophytes), may provide a viable alternative to increase productivity compared to conventional salt-sensitive crops, increasing the economic potential of salt-affected lands that comprise ~20% of irrigated lands worldwide. In this study the Agricultural Policy/Environmental eXtender (APEX) model was adapted to simulate growth of the halophyte quinoa, along with salt dynamics in the plant-soil-water system. Model modifications included salt uptake and salt stress functions formulated using greenhouse data. Data from a field site were used to further parameterize and calibrate the model. Initial simulation results were promising, but differences between simulated and observed soil salinity and plant salt values during the growing season in the calibration suggest that additional improvements to salt uptake and soil salinity algorithms are needed. To demonstrate utility of the modified APEX model, six scenarios were run to estimate quinoa biomass production and soil salinity with different irrigation managements and salinities. Simulated annual biomass was sensitive to soil moisture, and root zone salinity increased in all scenarios. Further experiments are needed to improve understanding of crop salt uptake dynamics and stress sensitivities so that future model updates and simulations better represent salt dynamics in plants and soils in agricultural settings.

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Agricultural Policy Environmental eXtender (APEX) Simulation of Spring Peanut Management in the North China Plain

Agronomy ◽

10.3390/agronomy9080443 ◽

2019 ◽

Vol 9 (8) ◽

pp. 443 ◽

Cited By ~ 5

Author(s):

Jie Zhao ◽

Qingquan Chu ◽

Mengjie Shang ◽

Manyowa N. Meki ◽

Nicole Norelli ◽

...

Keyword(s):

Agricultural Policy ◽

North China Plain ◽

North China ◽

Growth And Yield ◽

Pod Yield ◽

The North ◽

The North China Plain ◽

Sowing Dates ◽

Irrigation Depth ◽

Apex Model

Spring peanut is a valuable alternative crop to mitigate water scarcity caused by excessive water use in conventional cropping systems in the North China Plain (NCP). In the present study, we evaluated the capability of the Agricultural Policy Environmental eXtender (APEX) model to predict spring peanut response to sowing dates and seeding rates in order to optimize sowing dates, seeding rates, and irrigation regimes. Data used for calibration and validation of the model included leaf area index (LAI), aboveground biomass (ABIOM), and pod yield data collected from a field experiment of nine sowing dates and seeding rate combinations conducted from 2017 to 2018. The calibrated model was then used to simulate peanut yield responses to extended sowing dates (5 April to 4 June with a 5-day interval) and seeding rates (15 plants m−2 to 50 plants m−2 with a 5 plants m−2 interval) using 38 years of weather data as well as yield, evapotranspiration (ET), and water stress days under different irrigation regimes (rainfed, one irrigation before planting (60 mm) or at flowering (60 mm), and two irrigation with one time before planting and one time at flowering (60 mm each time) or at pod set (60 mm each time)). Results show that the model satisfactorily simulates pod yield of peanut based on R2 = 0.70, index of agreement (d value) being 0.80 and percent bias (PBIAS) values ≤4%. Moreover, the model performed reasonably well in predicting the emergence, LAI and ABIOM, with a R2 = 0.86, d = 0.95 and PBIAS = 8% for LAI and R2 = 0.90, d = 0.97 and PBIAS = 1% for ABIOM, respectively. Simulation results indicate that the best combination of sowing dates and seeding rates is a density of 35–40 plants m−2 and dates during early-May to mid-May due to the influence of local climate and canopy structure to the growth and yield of peanut. Under the optimal sowing date and plant density, an irrigation depth of 60 mm during flowering gave a pod yield (5.6 t ha−1) and ET (464 mm), which resulted in the highest water use efficiency (12.1 kg ha−1 mm−1). The APEX model is capable of assessing the effects of management practices on the growth and yield of peanut. Sowing 35–40 plants m−2 during early-May to mid-May with 60 mm irrigation depth is the recommended agronomic practice for peanut production in the water-constrained NCP.

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Markets for Purchased Farm Inputs

Voprosy Ekonomiki ◽

10.32609/0042-8736-2005-6-60-71 ◽

2005 ◽

pp. 60-71

Author(s):

E. Serova ◽

O. Shick

Keyword(s):

Agricultural Policy ◽

Financial Constraints ◽

Information Sources ◽

Animal Feed ◽

Government Policies ◽

Market Institutions ◽

Policy Makers ◽

Government Organizations ◽

The Impact ◽

Farm Inputs

Russian policy makers argue that agriculture suffers from decapitalization due to financial constraints faced by producers. This view is the basis for the national agricultural policy, which emphasizes reimbursement of input costs and substitutes government and quasi-government organizations for missing market institutions. The article evaluates the availability of purchased farm inputs, the efficiency of their use, the main problems in the emergence of market institutions, and the impact of government policies. The analysis focuses on five groups of purchased inputs: farm machinery, fertilizers, fuel, seeds, and animal feed. The information sources include official statistics and data from two original surveys.

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Cherneha O. B., Chepurnova A. V. COMPARATIVE ANALYSIS OF UKRAINE AND POLAND FOOD SECURITY LEVELS

TRADE AND MARKET OF UKRAINE ◽

10.33274/2079-4762-2019-46-2-9-17 ◽

2019 ◽

pp. 9-17

Keyword(s):

Food Security ◽

Comparative Analysis ◽

Rural Development ◽

Agricultural Policy ◽

Common Agricultural Policy ◽

Public Spending ◽

Development Program ◽

Rural Development Program ◽

Security Levels ◽

The Eu

Objective. The purpose of the article is to compare the levels and mechanisms of food security management in Ukraine and Poland, to identify the main factors influencing the processes of its formation and to determine the directions of increasing the level of Ukraine food security. Methods. The scientific results of the study were obtained using the following methods: theoretical generalization and comparison (for the study of meaningful aspects of the definition of «food security»), analysis and synthesis (for comparative analysis of Ukraine and Poland food security levels), abstract-logical method (for establishing the links between the level of economic development of countries and the levels of their food security and determining the directions of increasing the Ukraine level of food security). Results. On the basis of a comparative analysis of Ukraine and Poland food security levels, a significant gap in Ukraine’s provision of food security has been identified. Thus, with respect to all food security components identified by FAO, except for the «use» of sanitary and safe drinking water, Poland has reached far ahead of Ukraine. It has been found that for the period 2012–2018, the value of the Global Food Security Index for Ukraine decreased by 2.1 due to a decrease in the level of affordability and availability of food, while the Polish side increased its position on GFSI by 2.8 due to the increase in affordability and availability of food in the country. It has been found that the decisive influence on the level of food security in Poland, as well as high ranking in the ranking is carried out by the EU Common Agricultural Policy (CAP), the implementation of the Polish Rural Development Program and significant public spending on agriculture. It has been determined that the main directions for improving the level of food security of Ukraine should be: lifting the moratorium on the sale of agricultural land; financing the agri-food sector not only through public spending but also through EU programs; creation and implementation of the National Rural Development Program; full and unconditional implementation of Government programs on EU integration; adaptation to the EU Common Agricultural Policy standards.

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