Applied Engineering in Agriculture Vol. 24(3): 359‐369 E 2008 American Society of Agricultural and Biological Engineers ISSN 0883-8542 359 ESTIMATING THE ECONOMIC V ALUE OF RICE (ORYZA SATIVA L.) AS A FUNCTION OF HARVEST MOISTURE CONTENT T. J. Siebenmorgen, N. T. W. Cooper, R. C. Bautista, P. A. Counce, E. Wailes, K. B. Watkins ABSTRACT. The net value (NV) of rice, as affected by drying costs and milling quality changes associated with harvesting rice at various moisture contents (MCs), was studied using a five‐year data set comprising eight cultivars harvested over a range of MCs from 11 southern U.S. locations. A quadratic relationship was used to characterize the change in NV across harvest MC (HMC); this relationship was due to the progressively‐increasing fee structure for commercial drying costs and the quadratic nature of head rice yield (HRY) changes with HMC. A sensitivity analysis revealed that as the price of brokens increased, there was a slight decrease in the HMC at which NV was maximized. Relative to the price of brokens, the optimum HMC was not influenced by fluctuations in head rice price. At a given HMC, the NV of a rice bulk increased with the price of brokens, and the extent of the increase was heavily influenced by the HRY versus HMC relationship. In all instances, the optimal HMC to maximize HRY (HMC opt‐HRY ) was greater than the HMC corresponding to the maximum NV (HMC opt‐NV ). When HMC, NV and HRY were plotted regardless of cultivar, location, or harvest year, the MC at which HRY was maximized was 21.7% whereas the MC at which NV was maximized was 18.5%, representing a 3.2 percentage point difference between HMC opt‐HRY and HMC opt‐NV . Keywords. Rice, Head rice yield, Net economic value, Drying cost, Milled rice value. etermining the appropriate time to harvest is a crucial decision for rice producers. Upon maturity, the average moisture content (MC) and the distribution of individual kernel MC distributions vary dramatically depending on environmental conditions (Bautista and Siebenmorgen, 2005). These MC changes can correspond to milling quality changes. For example, if the harvest date is delayed and the rice field MC is allowed to decrease to ≤15% (all moisture contents have been expressed on a wet basis), there is a risk that environmental humidity could cause dry kernels to rapidly absorb moisture, which causes fissuring (Kunze and Prasad, 1978; Siebenmorgen and Jindal, 1986). Rice kernel fissuring would then result in low head rice yields (HRYs), the mass percentage of rough rice kernels that remain as head rice [milled kernels that are ≥75% in length of an intact rice kernel after complete milling (USDA, 2005)]. As rice is sold primarily as head rice, HRY is a key determinant of rice quality and therefore the value of rice. Broken rice, which is typically ground and sold as flour, is currently valued at 60% to 80% of head rice (USDA, 2007). At high harvest MCs Submitted for review in November 2007 as manuscript number FPE 7278; approved for publication by the Food & Process Engineering Institute Division of ASABE in April 2008. The authors are Terry J. Siebenmorgen, ASABE Fellow, University Professor, Nora T. W. Cooper, Program Associate, Rustico C. Bautista, Research Associate, Food Science Department, University of Arkansas, Fayetteville, Arkansas; Paul A. Counce, Professor, Rice Research and Extension Center, University of Arkansas, Stuttgart, Arkansas; Eric Wailes, Professor, Agricultural Economics Department, University of Arkansas, Fayetteville, Arkansas; and Kenton B. Watkins, Assistant Professor, Rice Research and Extension Center, University of Arkansas, Fayetteville, Arkansas. Corresponding author: Terry J. Siebenmorgen, 2650 N. Young Ave., Fayetteville, AR 72704; phone: 479‐575‐2841; fax: 479‐575‐6936; e‐mail: tsiebenm@uark.edu. (HMCs), HRY can also decrease, as the percentage of immature kernels increases with HMC. These immature kernels are typically thin and weak, and thus increasingly prone to breaking during milling (Siebenmorgen and Qin, 2005; Siebenmorgen et al., 2006; Bautista et al., 2007). Though there are other factors that can affect HRY, including combine cylinder speeds (Dilday, 1989), grain drying regimens (Schluterman and Siebenmorgen, 2007), and the presence of foreign matter, HMC is one of the foremost properties that indicate HRY potential. Optimal HMCs for maximizing HRYs vary with cultivar and location. In the mid‐Southern United States, Siebenmorgen et al. (2007) recommended harvesting long‐grain cultivars at MCs of 19% to 22% and medium‐grains at MCs of 22% to 24%, while in California, Mutters and Thompson (2006) recommended harvesting medium‐grains at greater than 21%. To a producer, it might seem logical to harvest at high MCs, when the rice is at the recommended HMC for maximizing HRY. However, high HMCs result in high drying charges. Drying charges are typically applied on a progressively‐increasing scale based on the HMC of a rice lot. It is vital to rice producers and to cooperatives to determine the most economical MC at which to harvest rice, taking into consideration drying costs and potential pre‐ harvest milling quality changes. Mutters and Thompson (2006), with a two‐year data set of California medium‐grain rice, reported that some of the HRY loss that resulted from harvesting at low MCs was counter‐balanced by lower drying costs to the producer, leading to a minimal loss of rice economic value. In California, rewetting in the field occurs mostly during conditions of heavy dew, when cool temperature conditions are coupled with relative humidity conditions that fluctuate diurnally (Mutters and Thompson, 2006). These conditions are different than those of the D