Demand for new mexico pod–type green chile in the United States has been rising for decades (Gandonou and Waliczek, 2013), yet domestic production has been declining because of both limited availability of labor and associated costs (Funk and Walker, 2010). Coinciding with reduction in New Mexico acreage (New Mexico Department of Agriculture, 2015) is a dramatic increase in imports of green chile from Mexico to the United States since 2009 (U.S. Agency for International Development, 2014). Hand labor accounts for an estimated 50% of green chile production costs in the United States (Eastman et al., 1997; Hawkes et al., 2008). Lower cost of hand labor in other countries has given a competitive advantage in overall lower production costs as compared with production in the United States. Red chile production labor costs were reduced to ≈10% (Eastman et al., 1997) when the crop was transitioned to mechanical harvest. If green chile production shifted to mechanical harvest, like red chile, this would level the playing field with competing countries.
In New Mexico, processing industries exist for both green and red chile. The red chile crop consists of physiologically mature fruit that is predominantly dried and ground into powders or used for extraction of red pigments to produce oleoresin paprika; the dried red fruit does not have to be whole or unblemished after harvest. The acceptability of fruit damage for red chile processors has driven the adoption of mechanization of red chile harvest. In New Mexico, 80% of the red chile crop is currently mechanically harvested (Bosland and Walker, 2004). By contrast, the new mexico green chile crop is 100% hand-harvested. High-quality green chile for the fresh market and processing must be undamaged, thick-walled fruit, ≈15–18 cm in length (Walker and Funk, 2014). Quality green chile is important because blemished or broken fruit will rot before reaching the fresh market or it will not move efficiently in a processing production line developed for whole unbroken fruit.
Transitioning new mexico green chile production to a mechanical harvest system has major challenges, primarily the unacceptability of broken or blemished fruit due to mechanical damage (Funk et al., 2011) and lack of an efficient method to mechanically remove the stems from the fruit (Herbon et al., 2009). To overcome these obstacles, a whole systems approach must be used (Rasmussen, 1968) as was seen in the 1960s when processing tomato (Solanum lycopersicum) production progressed into mechanical harvest. Tomato mechanical harvest success was propelled forward by the joint effort of engineers, horticulturists, and agronomists. Engineers created picking mechanisms, horticulturists developed cultivars for efficient mechanical harvest, and agronomists determined optimum field growing conditions. The same whole systems approach is being used for efficient mechanical harvest of green chile.
Joint research between New Mexico State University horticulturists and the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) Cotton Ginning Research Laboratory (Las Cruces, NM) determined that the inclined double open-helix picking head design was the most efficient green chile harvesting mechanism out of the several tested picking mechanisms (Funk and Walker, 2010). During this research in 2010, yield differences were identified between several new mexico pod–type green chile cultivars. Anecdotally, it was observed that plant architecture contributed to improved mechanical harvest efficiency; however, additional research was needed to identify the most important determinants of mechanical harvest quality/efficiency, such as plant height, plant width, number of basal branches, basal stem diameter, and height to first primary branch.
Mechanical harvest efficiency is the marketable fruit as a percentage of total plot yields. In an initial study of green chile mechanical harvest efficiency with the double open-helix picking mechanism, Funk and Walker (2010) reported 78% harvest efficiency of total plot yield. Research on mechanical harvest of green chile is limited, so determination of an acceptable benchmark for harvest efficiency has not been reported. Local farmers state that they would benefit from an 80% harvest efficiency for new mexico pod–type green chile (V. Hernandez, personal communication). As a benchmark for our study on new mexico pod–type green chile, 80% harvest efficiency was used.
Mechanical harvest efficiencies of red chile have been reported to be anywhere from 70% to 98% (Funk and Walker, 2010). Previous research on mechanical harvest of red chile found that certain plant architecture traits would improve mechanical harvest efficiency. These included upright plant habit with narrow branch angles and fruit set higher than the junction of the first primary branch (Marshall, 1984, 1997), fewer basal branches to reduce branch breakage and allow the picker to harvest without obstruction (Palevitch and Levy, 1984), and larger basal stem diameter at the soil level to lessen plant lodging (Kahn, 1985). Pendulous fruit that is evenly spread throughout the plant canopy with a low detachment force of the calyx from the fruit is also ideal for mechanical harvest (Wall et al., 2003). As a result of this research, a red new mexico pod–type ‘NuMex Garnet’ was released specifically for mechanical harvest traits (Walker et al., 2004). However, knowledge is lacking on whether plant architecture traits beneficial for red chile mechanical harvest would also benefit new mexico pod–type green chile mechanical harvest and on general information comparing mechanical harvest efficiency of currently available green chile cultivars. Identifying desirable plant architecture traits for mechanical harvest of green chile will improve harvest efficiency and drive breeding efforts in a direction that develops cultivars improved for mechanical harvest. In addition, data on mechanical harvest performance of current green chile cultivars would give growers and processors advice on which chile cultivars to grow when trying to transition their green chile crops to mechanical harvest.
The aim of this study was to evaluate six new mexico pod–type green chile cultivars consisting of breeding lines and common cultivars with various fruit and plant architecture traits and to determine their relative suitability for mechanical harvest. A whole systems approach was demonstrated in this research by incorporating previous engineering results on the most efficient picking mechanism (Funk and Walker, 2010) and agronomic results on best field management practices (Paroissien and Flynn, 2004; Wall et al., 2003) into the materials and methods for ideal assessment of these cultivars in a mechanical harvest system.
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