Grain sorghum (
Hybrid selection, plant population, and row spacing are variables that can have a significant impact on the net returns of sorghum producers. Though optimal plant densities for grain sorghum differ from region to region, previous research has indicated that grain yields generally increase as plant populations increase [
The row spacing in a crop can also impact crop yield potential [
Seedlings in close proximity to each other express phytochrome-mediated responses by developing narrow leaves, long stems, and less massive roots [
Major grain sorghum production regions in Texas include the upper Gulf Coast region which produces 8% of the Texas’ sorghum crop [
While the majority of grain sorghum is grown in rows with spacings ranging from 69 to 102 cm, some sorghum is planted broadcast [
The three-year (2001 to 2003) field study was conducted in Wharton County (29.12°N, 96.37°W) under conventional tillage system on the Richard Raun farm located near Louise, Texas. This field had previously been in rice (
Grain sorghum was planted on March 21, 2001, March 27, 2002, and March 12, 2003. Studies were conducted utilizing a randomized complete block design with a 2 × 2 × 3 factorial treatment arrangement with 3 replicates. The three factors included two grain sorghum hybrids (Dekalb (DK 54), Asgrow (A 571)), two row spacings (51, 102 cm), and three plant populations (148–160,000, 185–198,000, and 222–235,000/ha). Whole-plot treatments of sorghum hybrid were 12.7 m wide with row spacing and plant populations within each cultivar and 9.1 m in length. Fertilizer applied was based on the soil test recommendations provided by the Texas AgriLife Extension Service Soil and Plant Testing Laboratory. Fertilizer rates of 224 kg/ha of 24–12–6 were applied prior to planting and lightly disked into the soil surface approximately 2 to 3 weeks prior to sorghum planting. All treatments were planted flat or without a raised seedbed. Grain sorghum was planted with a Monosem vacuum planter (Monosem ATI, Inc., 17135 West 116th Street, Leneka, KS 66219) equipped with precision seed meters calibrated to deliver the desired seeding rate. Plant counts taken 4 to 6 wk after planting assured that each plot was within the desired plant populations. If any plots contained more than the desired plant populations, the excessive plants were hand-pulled from the plots. None of the plots contained less than the desired number of plants.
Crop yield was determined by harvesting the four rows of the 51 cm plots, and the two rows of the 102 cm plots with a small plot combine, and crop weights were adjusted to 14% moisture. Seed costs and grain sorghum prices were calculated based on April, 2012 prices (L. Falconer, personal communication). Seed costs were calculated at $6.60/kg (imidacloprid treated) while grain sorghum price was based on $9.00/45.4 kg. Net value per hectare was calculated by taking the yield/hectare, dividing by 45.4, multiplying by $9.00 then subtracting seed costs ($6.00, 7.50, 9.00 for 148–160,000, 185–198,000, or 222–235,000 seed/ha, resp.). Herbicide costs were figured constant across all row spacings and plant populations.
Data were subjected to ANOVA and analyzed using PROC GLM with SAS (SAS Institute, Inc., Cary, NC) and a model statement appropriate for a factorial design with sorghum hybrid, seeding rate, and row spacing as random effects. Treatments means were separated by Fisher’s protected least significant difference test at
Rainfall amounts were variable for the three years (Table
Monthly rainfall at the study location from 2001 to 2003.
Month | Monthly rainfall (mm) | |||
---|---|---|---|---|
2001 | 2002 | 2003 | 20 yr average | |
March | 88.9 | 33.0 | 45.7 | 80.8 |
April | 17.8 | 86.4 | 20.3 | 83.8 |
May | 182.9 | 55.9 | 2.5 | 119.3 |
June | 58.4 | 83.8 | 73.7 | 126.5 |
July | 20.3 | 396.2 | 332.7 | 83.1 |
| ||||
Total | 368.3 | 655.3 | 474.9 | 493.5 |
Since there was a grain sorghum hybrid by row spacing by plant population interaction for yield and net value in each year, data were not combined over years for statistical analysis.
In 2001, DK 54 planted on 51 cm centers at 185 to 198,000 plants/ha produced the greatest yield (Table
Grain sorghum yield as influenced by hybrid, row spacing, and seeding rate.
Hybrid | Row spacing (cm) | Plant population (1000’s/ha) | Yield response (kg/ha) | ||
---|---|---|---|---|---|
2001 | 2002 | 2003 | |||
Dekalb DK54 | 51 | 148–160 | 6686 | 3321 | 3070 |
185–198 | 7133 | 3770 | 3118 | ||
222–235 | 6106 | 3171 | 3313 | ||
102 | 148–160 | 5715 | 3269 | 3775 | |
185–198 | 6388 | 3420 | 2309 | ||
222–235 | 6308 | 3252 | 2859 | ||
| |||||
Asgrow A571 | 51 | 148–160 | 5799 | 3114 | 3265 |
185–198 | 6595 | 3877 | 2266 | ||
222–235 | 6336 | 3882 | 2607 | ||
102 | 148–160 | 5196 | 1948 | 3079 | |
185–198 | 5075 | 2913 | 2910 | ||
222–235 | 5173 | 2849 | 2578 | ||
| |||||
LSD (0.05) | 1116 | 1316 | 773 |
In 2002, grain sorghum yields were similar for all hybrids, row spacings, and plant populations with the exception of the A 571 planted on 102 cm centers with a plant population of 148 to 160,000 plants/ha which produced less than 2000 kg/ha (Table
In 2003, DK 54 planted on 102 cm centers with a plant population of 148 to 160,000 plants/ha produced the greatest yield (Table
It has been reported that the yield response to narrow rows in corn and grain sorghum is affected by many environmental, spatial, and temporal field interactions [
In 2001, the high rainfall for May (Table
Results for net dollar value were very similar to that found for yield (Table
Grain sorghum net dollar value per hectare minus seed costs as influenced by hybrid, row spacing, and seeding rate.
Hybrid | Row spacing (cm) | Plant population (1000’s/ha) | Net value over seed costs ($/ha) |
||
---|---|---|---|---|---|
2001 | 2002 | 2003 | |||
Dekalb DK54 | 51 | 148–160 | 1319.43 | 652.35 | 602.58 |
185–198 | 1406.49 | 739.86 | 610.72 | ||
222–235 | 1200.41 | 618.65 | 646.73 | ||
102 | 148–160 | 1126.92 | 642.00 | 742.35 | |
185–198 | 1258.80 | 670.7 | 450.27 | ||
222–235 | 1250.46 | 634.67 | 556.73 | ||
| |||||
Asgrow A571 | 51 | 148–160 | 1143.57 | 611.31 | 641.28 |
185–198 | 1305.84 | 761.10 | 441.69 | ||
222–235 | 1246.04 | 759.59 | 506.78 | ||
102 | 148–160 | 1024.05 | 380.19 | 604.38 | |
185–198 | 998.52 | 575.94 | 569.40 | ||
222–235 | 1015.46 | 554.75 | 501.02 | ||
| |||||
LSD (0.05) | 220.22 | 260.91 | 151.27 |
In the year when rainfall fell at the most opportune time, the narrow row spacings yields were slightly higher than the wide row spacings. However, in years when rainfall came at inopportune times, yields were variable. Results for the different populations were mixed. The lower plant populations did not always produce the greater yields especially in dryer years. Also, hybrid response was variable. Based on these results for this region, narrow rows may slightly help improve yields and profits. However, more research is needed to determine optimum plant populations, and also other hybrids need to be evaluated to determine if they may respond differently to narrow row plantings.
Responses to narrow row spacing in grain sorghum have been varied and inconsistent. Conley et al. [
Kevin Brewer, Dwayne Drozd, A.