Yield, nutritional quality, and profitability of green beans grown on a trellis using bean netting
Trellising with bean netting advisable for green beans, chickpeas, and peas
In this article we deal with the advantages of yield, profitability, and quality when using trellis bean netting (and not twine) for crops of green beans and chickpeas.
One of the strategies for raising yields and nutritional quality in agricultural regions is that of searching out cultivars with greater adaptation to different environmental conditions. The objective of this study was to classify green bean cultivars according to their phenology, growth, yield, nutritional quality, and profitability in a temperate climate with no irrigation. Three varieties with determinate growth (Opus, Strike, and Black Valentine) and one with indeterminate growth (Hav-14) were all planted May 7, 2008 at San Pablo Ixayoc, State of Mexico (Mexico) with a density of 6.25 plants·m-2 (0.64 plants/sq ft). Differences were found in life cycle, from 90 to 199 days for the final harvest, and also in yield and number of pods. These differences had the highest correlation with cumulative precipitation (PP, r= 0.83), the total evapotranspiration for the crop (ETc, r = 0.71) and accumulated thermal units (ATU, r = 0.65). The Opus variety showed the greatest percentage of minerals, phosphorus, ADF, lignin, NDF, and protein. The highest net income was achieved with Opus and Black Valentine. Notwithstanding, in a five-year period (average life of the trellis), Hav-14 is the most advantageous from an economical viewpoint. These results suggested that Hav-14 (with bean net for bean support), Opus, and Black Valentine would be the most appropriate cultivars for maximizing production under rainy season in the temperate climate of San Pablo Ixayoc (Mexico).
The green bean is a vegetable of importance in the diet of countries such as Turkey, the United States, Chile, Brazil, and Mexico, where the per capita consumption is 6.5, 3.5, 3.2, 1.2, and 1.1 kg. (14.3, 7.7, 7.1, 2.7, and 2.4 lbs) respectively. (Peixoto et al., 2001).
In Mexico its lower consumption is related to cultural factors given that in pre-Hispanic times beans were used more as shelled beans rather than as green beans (Kaplan, 1965). In addition, the cultivars currently used are poorly adapted and have an average yield of 3.7 t·ha-1 (1.7 T/A), which does not satisfy the internal demand of 1.1 kg (2.4 lbs) per capita (Salinas et al. 2008). Another factor that contributes to this low yield in areas of dry land farming is the scant and uneven distribution of rainfall (Roy et al., 2000).
In congruence with sustainable agriculture, which promotes better utilization of edaphic, genetic, water, and human resources that improve quality of life for the producer (Quintero et al., 2005), it is proposed that green bean cultivars, of both determinate and indeterminate growth, be identified which satisfy their water needs with available rainfall, and that increase yield and income for the producer.
At the present time, in the United States and France, over 120 cultivars of green beans have been developed including Blue Lake, Kentucky Wonder 765, Oregon, Black Valentine, Contender, Bronco, Strike, Opus, OR 900, Tender-green, Top Crop, AFN, Silvester, and La Victoria (Adsule et al.,2004) These have great yield potential with irrigation (more than 10 t·ha-1 or 4.5 T/A) and for which there is interest in corroborating their performance under the rainy season conditions of our country. However, yield for this crop, as well as for its direct components (number of pods, number of leaves, and leaf area index), are influenced by edaphic and environmental conditions (Roy et al., 2000; Abdel-Mawgoud et al., 2005) and specifically by the amount of rainfall and its distribution (Roy et al., 2000), the temperature (Tsukaguchi et al., 2005) and evapotranspiration (Omae et al., 2007). In addition, the nutritional quality of the green bean is affected by changes in the elements of the weather (Salinas et al., 2008). For this reason, it is necessary to identify the best yielding cultivars and those of the highest nutritional value that adapt to the geographical region of this study.
The objectives of the investigation were to study the phenology of the green bean, bean yield, and its direct components such as the nutritional quality of the bean for cultivars with different growth habits, and to determine the relationship between accumulated thermal units, evapotranspiration, and seasonal rainfall and the growth and yield of the bean.
Materials and Methodology
Characteristics of the Locale
The study was conducted during the rainy season at San Pablo Ixayoc, in the state of Mexico (19° 33′ N, 98° 47′ W, at 2,600 meters or 8530 feet above sea level). In this locale a temperate climate is found with summer rains, average annual temperature of 14.7 °C (58.5° F), and 609 mm (24 inches) of rainfall (García, 2005).
Samples and Experimental Design
The cultivars utilized were Opus, Strike, and Black Valentine, of determinate growth, and Hav-14 of indeterminate growth. Hav-14 was grown on a conventional trellis (poles supporting bean netting) and were planted May 7, 2008 at a density of 6.25 plants·m-2 (0.58 plants/sq ft), with a statistical design of randomly assigned plots with four repetitions.
Phenology and the vegetative stage (V-1: emergence, V-2: first pair of primary leaves, V-3: first pair of trifoliate leaves, and V-4: third pair of trifoliate leaves) and the reproductive stage (R-5: budding, R-6: flowering and F-7: fruiting) were recorded in accordance with the criteria presented by Escalante and Kohashi 1993).
Bean harvest took place every three days, when the pod had reached a length of 10 cm (3.9 inches). There was a total of seven pickings for which the weight of the fresh beans (kilograms per square meter) and number of pods (per square meter) were evaluated.
The morphological and physiological components of performance were evaluated 90 days after planting (DAP): stem length (LT in cm), number of nodes (NN), leaf area index (LAI, LA/m2), and duration of leaf area (DLA, in days).
The nutritional quality was determined by means of proximate chemical analysis (Sosa, 1979). The amounts of the following were determined: minerals (calcium and phosphorus), soluble carbohydrates, acid detergent fiber, lignin, neutral detergent fiber, hemicellulose, protein, and ether extract.
In order to determine dry matter weight, the bean pods were placed in a forced-air oven (THELCO, model 28) at 55°C (131° F) until obtaining a stable weight. Afterwards the percentage of moisture of the pods was determined as well as the difference quotient between the as-harvested and dry matter weights, multiplied by 100. The dry matter samples were ground in an electric grinder (a German-made JANKE AND KUNKLE INKA, Model Kb 5/10) with a 5-micron sieve.
Indices and Climatic Components
Accumulated thermal units (ATU °Cd, Snyder, 1985) were calculated weekly from planting until the last picking. Base temperature (Tbase) was considered to be 10 °C (50 °F) (Barrios-Gómez y López-Castañeda, 2009).
Evapotranspiration of the crop (ETc, mm·d-1, Doorenbos y Pruitt, 1986) was calculated, and cumulative precipitation (PP, in mm) recorded. A financial analysis was also done, calculating gross income on the basis of six Mexican pesos·kg-1 ($0.15 USD /lb) of beans (Anonymous, 2011). In accordance with the criteria established by Volke (1982), fixed cost was assigned to land cost. Variable cost was considered to be soil preparation, the seed, agro chemicals, labor, and the trellis with bean netting (in the case of the cultivar with indeterminate growth).
With exception of days until the occurrence of a phenological phase, the traits evaluated were subjected to variance analysis and Tukey’s means comparison test (P ≤ 0.05). Also, the correlation between yield and the climatic indices from the statistical packet SAS (Anonymous, 2002) were analyzed.
Results and Discussion
Phenology of the Green Bean and its Relationship with Temperature and Rainfall
The cultivars with determinate growth showed the shortest average cycle (from planting to end of harvest) with 93 days. By comparison, Hav-14 with indeterminate growth had 119 days. In the vegetative stage (from V-1 to V -4), Opus was the shortest (16 days), and Hav-14 the longest (22 days). The same tendency was observed in the reproductive stage (R-5 y R-6), with 51 and 69 days, respectively.
Nevertheless, for days to first picking and to seventh picking, Strike registered 68 and 90 days, respectively, while Hav-14 had 96 and 119, respectively. These differences in the occurrence of the phenological stages in relation to the growth habit of the bean, have also been reported by Esquivel-Esquivel et al. (2006). The longer cycle of Hav-14 with bean netting (119 days) is due to the fact, that during its reproductive stage, the production of leaves, branches, flowers, and fruits continues, which is characteristic of cultivars with type IV indeterminate growth, (Salinas et al., 2008; Garduño-González et al., 2009; Díaz-López et al., 2010). This (plus being on a bean support) permits it more time to capture the sun’s radiation and available moisture (cumulative rainfall of 415 mm (16.3 inches), 394 mm (15.5 inches) effective rainfall), contrasting with determinate growth cultivars (383 and 364 mm (15.1 and 14.3 inches), respectively). The maximum and minimum temperatures of 21.3 and 9.4 ºC (70.3 and 48.9 ºF) were of no consequence in the phenology of the cultivars since they were practically constant during the biological cycle.
Bean Yield as a Function of ATU, ETc, and PP
The yield and number of pods of the indeterminate cultivar, Hav-14 (with bean netting), were statistically similar to Opus and Black Valentine, and superior to Strike. Furthermore, Hav-14 had the highest values for ATU, ETc, and PP during its cycle. By contrast Strike showed the lowest values.
The long cycle cultivars (119 days), like Hav-14, have inputs for growth available for a longer period of time and being under irrigation would be advantageous to them for increasing the number of pickings and bean yield. However, under conditions of seasonal rainfall, it should be taken into account that the rainfall does not follow a defined pattern in its frequency and distribution during the year. Thus, the crop can suffer water stress, especially during the reproductive stage, which could cause reduced yield or even total loss of the crop. Yield showed the highest correlation with precipitation (r = 0.83, P ≤ 0.01), followed by evapotranspiration of the crop (r = 0.71, P ≤ 0.05), and, lastly, thermal units (r = 0.65, P ≤ 0.05).
It is worth noting that the yield of Hav-14 (with the bean netting), Black Valentine, and Opus was twice as good as the average yield reported for the region, which is 2.8 t·ha-1 (1.3 T/A) (Anonymous, 2011). Said differences in length of crop cycle, ATU, and yield for cultivars of different growth habit, have also been found for shelling beans (Escalante-Estrada y Rodríguez-González, 2010), which suggests that ATU can be an appropriate indicator for the time of occurrence of the phenological stages of the bean and its yield.
Similar tendencies have been observed in the relationship between yield, PP, and ETc Escalante et al.,2001; Salinas et al., 2008). The average yield and number of beans of this study of 0.452 kg·m-2 [sic] and 113.5 ·m-2 [sic] (1.5 oz/sq ft and 10.5/sq ft), respectively, was less than that reported by Esquivel-Esquivel et al. (2006), who found an average yield of 10 t·ha-1 (4.5 T/A). However, this was achieved with the help of two rounds of irrigation in addition to the seasonal rainfall. As it was, in this study the lower PP during the crop cycle (394 mm or 15.5 inches), limited the yield potential of Hav-14, given that a yield of 10 t·ha-1 (4.5 T/A) has been reported with 578 mm (22.8 inches) in the same locality and soil type and a similar planting date (Díaz-López et al., 2010).
Morphological and Physiological Components of Yield
At 90 DAP only the number of nodes and stem length showed statistical variation between the cultivars. The Hav-14 cultivar (grown on bean netting) had the most nodes and a stem 181 cm (7.1 inches) in length, similar to that reported by Díaz-López et al. (2010), and followed by Black Valentine, Opus, and Strike. This behavior is associated with growth habit since Hav-14, of type IV indeterminate growth, shows vegetative buds on the main stem and branches during the reproductive stage. In contrast, the determinate growth cultivars have a reproductive terminal bud at their apex, which stops their vegetative growth (Escalante y Kohashi, 1993).
Likewise, Hav-14 had LAI and DLA values statistically similar to Black Valentine and Opus but superior to Strike, which had the lowest values. This indicates that the longer-lasting photosynthetic activity of Hav-14, Black Valentine, and Opus, by increasing the production of photosynthates and transferring them to the reproductive parts, increased the number and harvest weight of the green beans. Differences in the leaf area index and duration of leaf area among cultivars of different growth habits for shelling beans were detected by Escalante y Rodríguez (2008) y Escalante-Estrada y Rodríguez-González (2010).
The variance analysis of the nutritional quality traits revealed significant differences among cultivars. Opus had the highest values (P ≤ 0.05) for minerals, phosphorus, acid detergent fiber, lignin, and neutral detergent fiber, while Hav-14 had the lowest (in the case of lignin and phosphorous, along with Black Valentine). Nevertheless, the percentage of soluble carbohydrates was greatest for Hav-14 and least for Opus. This indicates that as fiber content increases, soluble carbohydrates decrease. A similar tendency in Hav-14 was found by Salinas et al. (2008) with different planting dates. Moreover, the nutraceutical importance of food fiber should be highlighted, given that consumption of 25 to 30 g·día-1 (0.9 to 1.1 oz/day) reduces predisposition to chronic illnesses such as arterial hypertension, type II diabetes, constipation, and colon cancer (Zezola y Ramos, 2008).
In general, no significant differences were seen between growth habits for percentage of phosphorous, hemicellulose, and ether extract. However, there were differences for minerals, acid detergent fiber, lignin, neutral detergent fiber, and protein. The determinate cultivars had the highest values. Similar results were reported by Esquivel-Esquivel et al. (2006). This indicates an inverse relationship between green bean yield and the nutritional variables due to a phenomenon of dilution, as was also found between sunflower protein content and biomass (Escalante et al., 1998).
Differences for profitability among green bean cultivars were observed. The Opus cultivar with $ 10,056.00 (Mexican peso) was most profitable, followed by Black Valentine with $ 9,856.00. Strike and Hav-14 showed losses of $ 9,444.00 and $ 24,940.00, respectively. In the case of Strike the loss was due to low yield (1,954 kg·ha-1 or 1,744 lbs/A) and for Hav-14 because of the added variable costs (poles and bean netting for a trellis).
If the net income mentioned is calculated for a five-year period (the life expectancy of the bean support) using the same cultivars, fixed and variable costs, yield, and price per kilogram of beans, then the following would result: Hav-14 would be most profitable, followed by Opus, and then Black Valentine ($ 85,480.00, $ 50,276.00, $ 49,076.00, respectively). In this scenario the Strike cultivar would end up with a loss of $ 42,224.00. Garduño-González et al. (2009) reported a similar finding with respect to the profitability of the indeterminate climbing bean using trellis bean netting.
The above results suggest that the green bean, besides being a nutritious food, is an alternative for increasing income for the produce grower. It is to be expected, that in regions with climatic conditions similar to the ones in this study, similar results would be obtained for yield, nutritional quality, and income, which would improve quality of life for the producer.
In San Pablo Ixayoc, in a temperate climate and during rainy season conditions, the Hav-14, Opus, Black Valentine, and Strike cultivars show differences in the phenology, yield, and nutritional quality.
The best yield was achieved with the Hav-14 cultivar, followed by Opus and Black Valentine, and the lowest with Strike.
Nutritional quality was highest for Opus, followed by Black Valentine, Strike, and Hav-14.
The differences in growth and yield are positively related to rainfall, evapotranspiration from the crop, and accumulated thermal units during the crop cycle.
The most net income was obtained with Opus and Black Valentine.
Rev. Chapingo Ser.Hortic vol.19 no.3 Chapingo sep./dic. 2013
Nicolás Salinas-Ramírez; José Alberto Salvador Escalante-Estrada; María Teresa Rodríguez-González; Eliseo Sosa-Montes
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