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Fluid Journal : Fluid Journal 1996-1998
2 Fluid Journal Fall 1997 March 15 and April 2 plantings, with starters increasing yield by about 8 bu/ A at each of these planting dates (Figure 1). Although grain yield was lowest at the April 28 planting, yield response to starters compared to the check was much larger than the responses at the earlier dates. This larger response for the late planting date was unexpected, but may have been due to higher than normal rainfall in April. More importantly, a 3.2-inch rainfall occurred soon after April 28, which may have resulted in cooler soil temperatures and compact soil. 1992. Optimal planting dates were mid-March through mid-April (Figure 2). Although mid-April to early-May was considered late, yields were higher than expected. As mentioned above, main effect of starter was not significant. 1993. Starter increased yield at two of four planting dates (Figure 3), resulting in a planting-date-by-starter interaction. March and April temperatures were below normal, which was conducive to yield responses from a P starter. Highest overall yield occurred at the March 15 planting. The low yield and lack of starter response at the April 1 planting may have been related to a southern green stinkbug infestation Hybrid Hybrid by starter by year interaction for grain yield was significant, indicating that the hybrid by starter interaction was not consistent across years. However, there were no negative responses to starters among the hybrids evaluated in this study. 1991. The hybrid by starter interaction was significant. Four of the six hybrids showed an increase in grain yield from application of starter fertilizer (Figure 4). 1992. Neither the starter main effect nor hybrid by starter interaction was significant (Figure 5). However, the highest yields of the study were produced in this year. Climatic conditions were most favorable for corn plant development, with yields averaging 170.5 bu/A. While our findings suggest that yield increase from starters is least likely in years with good growing conditions, climatic conditions may not entirely account for differences in responses to starters, especially in 1991 where large yield responses were noted at late planting dates. 1993. The starter effect was significant and the hybrid by starter interaction was not. However, three of the six hybrids showed a trend toward higher yields when starter was applied (Figure 6). Conclusion Although yield responses to starters were inconsistent across years and planting dates, corn responded to starter in two of three years, with significant yield responses in 5 of 11 year-planting date comparisons. Optimal yield occurred when corn was planted early (from mid-March through early April). Planting from early to mid-March and using starters help ensure consistent maximum yield and minimal conflict with cotton production practices in both spring and fall. Methodology Site. Dryland field study was conducted at the Northeast Research Station near St. Joseph, Louisiana. Soil was a Commerce silt loam (fine silty, mixed, thermic, nonacid, Aeric Fluvaquent). Hybrids were Delta and Pineland G-4666 and 5750, Terral SB 1802 and SB 1876, Pioneer 3165, and Asgrow RX947. Starter treatments consisted of ammonium polyphosphate (11-37-0) applied in-furrow, and no starter (or check). It was not obvious and could not he determined if growth and yield responses to starter were due to the N or P component of the ammonium polyphosphate applied. Application. Rate of starter application was 3 gal/A in 1991, 4 gal/A in 1992 and 1993. In 1991, the planter Figure 1. Starter and planting date influence on corn yield. Data averaged across six hybrids. Mascagni and Boquet, LSU, 1991. Figure 2. Starter and planting date influence on corn yield. Data averaged across six hybrids. Mascagni and Boquet, LSU, 1992. Figure 3. Starter and planting date influence on corn yield. Data averaged across six hybrids. Mascagni and Boquet, LSU, 1993. Yield - bu/A Yield - bu/A Yield - bu/A 1991 1992 1993 Starter No Starter Starter No Starter Starter No Starter 190 190 190 175 175 175 160 160 160 145 145 145 130 130 130 115 115 115 15 Mar 13 Mar 15 Mar 2 Apr 1 Apr 1 Apr 16 Apr 19 Apr 28 Apr 1 May 7 May
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