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Topographic variability is one of the main factors that affect soil properties and crop production. In this work, we reviewed the concept and significance of various topographic attributes and their influence on the factors contributing to crop growth and yield, including soil physical, hydraulic, chemical, and biological properties and nutrient distribution as affected by landscape positions. The effects of topography on soil properties and crop growth and yield depend on soil type and depth, climate, cropping system, and management practices. Accurate elevation data and its derived topographic attributes have broad applications in precision agriculture, including site-specific applications of seed, fertilizer, and water, management zone delineation, designing contours or terraces and precision leveling plans, and planning soil and water conservation programs for enhanced profitability. This work revealed the lack of research in application of secondary topographic attributes in agriculture and on-farm research in using topography in site-specific management of crop inputs. Interdisciplinary research efforts is suggested to enhance the understanding and promote application of topographic information in precision agriculture. Furthermore, there are needs to raise the awareness of producers to use the built-in real-time kinematic (RTK) Global Navigation Satellite System (GNSS) technologies to collect accurate three-dimensional data for site-specific management. In addition, this work suggested the need for user-friendly tools to help producers employ the collected topographic data to achieve precision agriculture goals. [ABSTRACT FROM AUTHOR]

Agriculture faces the challenge of feeding a growing population with limited or depleting fresh water resources. Advances in irrigation systems and technologies allow site-specific application of irrigation water within the field to improve water use efficiency or reduce water usage for sustainable crop production, especially in arid and semi-arid regions. This paper discusses recent development of variable-rate irrigation (VRI) technologies, data and information for VRI application, and impacts of VRI, including profitability using this technology, with a focus on agronomic factors in precision water management. The development in sprinkler systems enabled irrigation application with greater precision at the scale of individual nozzle control. Further research is required to evaluate VRI prescription maps integrating different soil and crop characteristics in different environments. On-farm trials and whole-field studies are needed to provide support information for practical VRI applications. Future research also needs to address the adjustment of the spatial distribution of prescription zones in response to temporal variability in soil water status and crop growing conditions, which can be evaluated by incorporating remote and proximal sensing data. Comprehensive decision support tools are required to help the user decide where to apply how much irrigation water at different crop growth stages to optimize water use and crop production based on the regional climate conditions and cropping systems. [ABSTRACT FROM AUTHOR]