Verifying optimality of rainfed agriculture using a stochastic model for drought occurrence
Verifying optimality of rainfed agriculture using a stochastic model for drought occurrence
复制标题
使用干旱发生的随机模型验证雨养农业的最优性
DOI：
10.1007/s00477-015-1129-y
复制
发表时间：
2016
影响因子：
4.2
通讯作者：
Fujihara M
中科院分区：
文献类型：
--
作者：
Sharifi E;Unami K;Yangyuoru M;Fujihara M
这可能是自相矛盾的，但生计型农业是撒哈拉以南非洲的主要粮食来源，那里的生产不确定性与降雨的随机性有关。本文试图通过数学方法来理解这种情况的基本原理。考虑干旱程度为零回复的Ornstein-Uhlenbeck过程，在随机控制理论的背景下研究了农业生产的最优性。用第一个退出时间的概念模拟了干旱终止作物生长的发生。以灌溉努力量为控制变量，建立了考虑灌溉虚拟成本、作物水分胁迫和农业效益的随机控制问题。研究了控制最优控制的Hamilton-Jacobi-Bellman方程，用反问题方法确定了优化集约农业的成本函数集。在加纳沿海热带稀树草原农业生态区收集数据和信息，以确定模型参数，制定随机控制问题，解决反问题，然后验证最优的农业。结果表明，当作物对水分胁迫的耐受性较强时，种植农业不是最佳的。
It may be paradoxical but subsistence rainfed agriculture is the predominant source of food in Sub-Saharan Africa where the production uncertainty is associated with the stochastic nature of rainfall. This paper attempts to comprehend the rationale of this situation by a mathematical approach. Considering the level of drought severity as the zero-reverting Ornstein–Uhlenbeck process, optimality of rainfed agriculture is investigated in the context of stochastic control theory. Occurrence of drought terminating growth of crops is modelled with the concept of first exit time. A stochastic control problem allowing for virtual cost of irrigation, water stress to crops, and benefits of farming is formulated with irrigation effort as the control variable. The Hamilton–Jacobi–Bellman equation governing the optimal control is studied to identify the set of cost functions optimizing rainfed agriculture in an inverse problem approach. Data and information were collected in the coastal savanna agro-ecological zone of Ghana, to identify model parameters, formulate the stochastic control problem, solve the inverse problem, and then verify optimality of rainfed agriculture. The results indicated that rainfed agriculture is not optimal when the crop is more tolerant to water stress.