Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/10/2006
Publication Date: 7/10/2006
Citation: Colaizzi, P.D., Evett, S.R., Howell, T.A. 2006. Crop emergence and near-surface soil temperature for SDI, LEPA, and spray irrigation. Paper Number 062278, 2006 ASAE Annual Meeting. Available: http://asae.frymulti.com/request.asp?search=1&JID=5&AID=22304&CID=por2006&T=2. Interpretive Summary: Approximately 72 percent of the irrigated area in the Texas High Plains use center pivot irrigation systems; however, subsurface drip irrigation (SDI) is being increasingly adopted in this region. Many cotton producers perceive SDI to result in greater crop yield per amount of irrigation water applied, warmer soil temperatures, and earlier cotton maturity relative to center pivot systems. This is thought to be related to reduced evaporative cooling of the soil surface and plant canopy, since SDI applies water beneath the soil surface in the plant root zone. However, crop germination and emergence have been serious limitations with SDI if preplant precipitation was inadequate. We compared crop emergence, crop yield, and near-surface soil temperatures for sprinkler packages (i.e., spray and LEPA) commonly used with center pivot systems and for SDI. We also varied irrigation application rates to simulate the range of irrigation capacities common in the High Plains. This paper reports the results of the 2005 season. We originally planted cotton, but had to replant the field in soybeans following complete destruction of the cotton crop by hail. Soybean emergence was less with SDI at all irrigation rates; however, at low irrigation rates, SDI resulted in greater soybean grain yield and water use efficiency compared with LEPA or spray irrigation. At high irrigation rates, grain yield was greatest with spray irrigation. At all irrigation rates, SDI maintained greater early-season soil temperatures than LEPA or spray irrigation, although at low irrigation rates toward the end of the season, soil temperatures with SDI were less than those under spray. This may have been related to greater plant vigor and enhanced soil shading with SDI.
Technical Abstract: Soybean emergence, grain yield, seasonal water use, water use efficiency (WUE), and irrigation water use efficiency (IWUE) were compared for four irrigation methods and five irrigation rates during the 2005 season. The irrigation methods were mid-elevation spray applicators (MESA), low-elevation spray applicators (LESA), low energy spray applicators (LEPA), and subsurface drip irrigation (SDI). Irrigation rates were 0%, 25%, 50%, 75%, and 100% of the full crop water requirement. Soybean emergence was less with SDI compared with MESA, LESA, and LEPA for all irrigation rates. Grain yield, WUE, and IWUE were greater for SDI at the 25% and 50% irrigation rates, but MESA resulted in greater grain yield, WUE, and IWUE at the 100% irrigation rate. Near-surface soil temperatures were also measured for each irrigation method but at the 50% and 100% irrigation rates only. Soil temperatures were compared in terms of cumulative soil heat units (CSHU). Early season CSHU were significantly greater for SDI at both the 50% and 100% irrigation rates. At the 50% rate, CSHU for MESA and LESA became greater than SDI by V4 to V6 stage, possibly because SDI plants had greater vigor and increased soil shading. At the 100% rate, CSHU for SDI was greater than MESA or LESA throughout the season. LEPA resulted in the least CSHU at the 50% rate, but had the greatest CSHU at the 100% rate. However, the LEPA results may have been affected by run on and run off of irrigation water due to furrow dike erosion.