Growth and Yield of Snap Beans as Affected by Wind Protection and Microclimate Changes due to Shelterbelts and Planting Dates

The effects of wind protection on growth and total and marketahle yields of snap hean tPhaseolus vulgaris L.) planted at 2-week intervals through the 1994 and 1995 growing seasons were examined. Research was conducted under nonirrigated conditions at the Shelterhelt Research Area, Univ, of Nebraska Agricultural Research and Development Center (ARDC) near Mead. 'Strike' <white-seeded) and 'Rushmore' (dark-seeded) were planted in locations sheltered from wind stress hy tree windhreaks (shelterhelts) and in locations exposed to normal winds using a randomized complete-block design with a split-split plot arrangement of treatments. Air temperature, soil temperature, humidity, wind speed, and wind direction were monitored. Detailed microclimate conditions at hean canopy level in sheltered and exposed plots are provided in the text. Wind speed in sheltered areas averaged 36<'(" of open field wind speed in 1994 and 43% of open wind speed in 1995. Soil temperatures were higher in sheltered areas than in exposed areas. Microclimate changes due to shelter had no effect on the percent seedling emergence or number of days to emergence. Plants in shelter had significantly higher total dry weight and leaf area index and greater total internode length than exposed plants. Both total and marketable yields were increased significantly hy production under sheltered conditions each year. Planting date and cultivar also had a significant impact on average pod yields. No interactions hetween shelter and planting date, or shelter and cultivar, were found in either year. The results suggest that wind protection provided hy shelterhelts (tree windhreaks) can increase pod yields of snap bean both early and late in the season. This may result in greater profit Ior the grower due to a tendency for higher prices at these times. break systems comprised the four randomized replications of the sheltered treatment. Each windbreak consisted of two rows of green ash iFraxinus pcnnsvlvanica L.). eastern red cedar Uunipcrus virginiana L.), and Austrian pine (Pinus nigra Arnold). arranged as mixed pairs of the possible combinations. The average height and width of the shelterbelts during the study period were 13 and 14 m. respectively. In eastern Nebraska. the prevailing winds arc mainly from the south or southwest during the growing season (May-September). Sheltered crops were planted between I and 2 H (H representing the height of the shelterbelts) leeward or tourcast-west oriented shelterbelts established in 1966. Vegetable plots were at least 7.(,2 m from either end of each shelterbelt to avoid wind eddy effects in this area. Exposed treatment plots were at least 15 Hand not directly downwind lrom any shcltcrhclr. Both sheltered and exposed plots were 650 m in 1994 and I 115 m' in 1995. The soil is Typic Arguidoll (Sharpsburg si Ity c lay loam recently reclassified in the Aksurbcn series). Microclimatc conditions in each or the eight main plots were monitored hy measuring wind speed, air and soil temperatures. relative humidity (RH) using an automated CR I 0 data loggcr (Campbell Scientific. Logan, Utah) in each plot arc.: lor a total or cight data logger sysrcm«. Each datalogger system included an air temperature/relative humidity sensor, an anemometer tor wind speed and a wind dircction sensor. Cup anemometers (mode! 12102: R.M. Young. Traverse City. Mich.) were used to measure wind speed at a height or 0,5 III aboveground. Air temperature and RII were measured at 0,4 m hcight using temperature and RH probes (models HMP-,5 and CS500: Ctuupbc!l Scientific). Most research on plant rcsponsc to wind strcss has used scnsorx only at the standard mctcrologicul hciuht or -' rn. Since wind speed is reduced by friction at ground level, we selected 0.5 m as more comparable to snap bean crop canopy hciuht. The .mcmomcicr and AT/RII sensors were locatcd on the north cdge or thc plots, adjacent to the last bean row farthest from the windbreak. at half the length or the vcgetable plot. and at comparable distance lrom the last row in the cxpuscd plots. Due to lear interference when the canopy closes, the anemometer cannot actually be in the plant rows. Temperature probes were calibrated to ±O.5 "C accuracy each ycar. Humidity senSdrs were calibrated to ±2'!r, accuracy each year. Microclimate data were mcasurcd cvery minutc. with hourly and daily avcragcs recorded. Soil tempcraturc was mcasurcd using soil thcrnlOcouple probcs (TCAV. Camphell Scientific) at 7.5 cm. Soil water was measurcd weckly throughout thc study by the gravimetric method. Ten soil samples to a depth of 30 cm were randomly collected each week for each planting within each plot. thcn mixed and subsamplcd. Plots were not irrigated. Two snap bean cultivars, 'Strike' and' Rushmore' (Seminis. Oxnard. CaliL), were used for the study. 'Rushmore' is a dark-seeded hean while 'Strike' is white-seeded. In 1994. seven plantings were made from 25 Apr. through 2 Snap heans wcrc planted in thc sumnlcrs of 1994 and 1995 at the 259-ha Shelterhelt Research Area.LJ niv, ofNehraskaAgricultural Research and Dcvelopment Center, ncar Me:td (41 "29 'N latitude. 96°25 'W longitude, 354 m ahove sea level). The two treatments applied were wind sheltered and exposed with four replications or each treatment for a total of eight main plots each year. Snapbean plots in four independent. identical mature windMaterials and Methods tcr plays in snap bean growth and production have been studied (Hagley, 1964: Hagley and Gowen. 1960: Roscnhcrg. 19('(), 19()7: Shah. 19(2), hut its influence with variation in planting datc and cultivar arc yct to be determined. This research was undertaken to relate spccilic environmental tuctor-, in sheltered and exposed locations to changc-, in snap bcun growth and development. to study the influence olplunt inu date on the total and marketable pod yields or two cultivars grown under sheltered and cxposcd conditions. and to quanti fy yiclds and linancial hcnelits ohtaincd from snap hcans grown under thc two systcms. Rcccived for puhlication 6 Aug. 2002. Accepted for puhlication l) May 2003. ,1ournal serics131 (]9 Ncbraska Agricultural Research Division, Univ. of Nehraska. Use of Irade names does not imply cndorscmcnt of thc products namcd nor criticism of similar ones not named. Research was supported hy the Mcintire-StennisCooperativcForcstryRcscarch Program and CSREES Project NE20-050. I Fonner graduate student. C'urrcntaddrcss: School ofApplicd Scicnces,MARA[nstituteofTechnology, 40450 Shah Alam, Malaysia. Snap beans arc a wann-scason crop with little Iros: tolerance and vcry low tolcruncc to physical damauc from wind and wind-blown soil (Finch. 19XX). Investigations of shelter effects on erop production attempt to predict quantitatively the effect or reduction or wind speed hy harriers on microclimate and crop performance. Once emerged, the sheltered crop interacts with and modifies the microclimate (Roscnberz et al., 19X3). In snap beans. the harvest is or primary interest. and earliness to markct is dircctly relatcd to pricc (Ncild and Greig, 1972), Harvest duration is or major economic importancc to maximi/l: thc timc in the market. Many aspects or the role that shel996 HORTSCtDICE VOL. 39(5) AU(;UST 2004 HortScience (August 2004) 39(5): 996-1,004.