Apple Fruit Diameter and Length Estimation by Using the Thermal and Sunshine Hours Approach and Its Application to the Digital Orchard Management Information System

<div><p>In apple cultivation, simulation models may be used to monitor fruit size during the growth and development process to predict production levels and to optimize fruit quality. Here, Fuji apples cultivated in spindle-type systems were used as the model crop. Apple size was measured during the growing period at an interval of about 20 days after full bloom, with three weather stations being used to collect orchard temperature and solar radiation data at different sites. Furthermore, a 2-year dataset (2011 and 2012) of apple fruit size measurements were integrated according to the weather station deployment sites, in addition to the top two most important environment factors, thermal and sunshine hours, into the model. The apple fruit diameter and length were simulated using physiological development time (PDT), an indicator that combines important environment factors, such as temperature and photoperiod, as the driving variable. Compared to the model of calendar-based development time (CDT), an indicator counting the days that elapse after full bloom, we confirmed that the PDT model improved the estimation accuracy to within 0.2 cm for fruit diameter and 0.1 cm for fruit length in independent years using a similar data collection method in 2013. The PDT model was implemented to realize a web-based management information system for a digital orchard, and the digital system had been applied in Shandong Province, China since 2013. This system may be used to compute the dynamic curve of apple fruit size based on data obtained from a nearby weather station. This system may provide an important decision support for farmers using the website and short message service to optimize crop production and, hence, economic benefit.</p></div

Comparison between estimated and measured fruit size values in 2011 and 2012 using the PDT model.

<p>Comparison between estimated and measured fruit size values in 2011 and 2012 using the PDT model.</p

Model implementation in a digital orchard management information system.

<p>Model implementation in a digital orchard management information system.</p

Comparison between estimated and measured fruit size values in 2013 using the PDT and CDT models.

<p>Comparison between estimated and measured fruit size values in 2013 using the PDT and CDT models.</p

Schematic showing the use of digital orchard management information system.

<p>Schematic showing the use of digital orchard management information system.</p

Error analysis of fruit diameter and length simulation in the spring and autumn of 2011, 2012, and 2013.

<p>^t and ^u: Regression coefficient determined by simple linear regression <i>Y = a+bX</i>, where estimated values = <i>X</i>, measured values = <i>Y</i>;</p><p>^v: coefficient of determination;</p><p>^w: Willmott agreement index;</p><p>^x: Mean absolute error;</p><p>^y: Mean bias error;</p><p>^Z: Root mean square error.</p><p>Error analysis of fruit diameter and length simulation in the spring and autumn of 2011, 2012, and 2013.</p

Comparison between estimated and measured fruit size values in 2011 and 2012 using the CDT model.

<p>Comparison between estimated and measured fruit size values in 2011 and 2012 using the CDT model.</p