Influence of Row Configuration_ Single Row_ Twin Row_ and Wide Bed

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					   Influence of Row Configuration (Single Row, Twin Row, and Wide Bed),
          Seeding Rate, and Nitrogen Rate on Grain Sorghum Yield

                            H.J. “Rick” Mascagni, Jr. and Bubba Bell

         Although sorghum is relatively tolerant to drought stress, maximum yield is possible only
when plant growth and development is not restricted by environmental conditions. Yields
fluctuate from year to year primarily because of varying environmental factors such as rainfall
and temperature. Irrigation has been used in recent years for many of the row crops, including
cotton, corn, and soybean, to lessen plant stress during times of low rainfall. Irrigation is a
management tool that can better ensure yield stability over time. Traditionally, sorghum has not
been irrigated because of its perceived tolerance to moisture stress and more importantly, to the
step-child production philosophy of using minimal inputs for producing the crop. For maximum
yield production, information is needed on the benefits of irrigation and the interaction of
irrigation with other production practices.

         When using irrigation, other cultural practices such as row spacing and seeding rate may
need to be modified for maximum yield. Research has indicated a consistent increase in grain
sorghum yield when rows are narrowed from the traditional 36 to 40-inch row spacing.
Narrowing the rows provides a more equidistant spacing among plants which increases the
efficiency of light and moisture utilization. In recent years, planters have been introduced that
have the capability of planting twin rows on raised beds. For example, commercial planters are
available that plant two rows, 9.5-inches apart, on top of raised beds. Also, raised wide beds (76-
to 80-inches wide) are becoming more common. On these beds, four 15-16-inch rows can be
planted. This planting strategy improves drainage and permits use of furrow irrigation. Optimum
seeding rate and nitrogen rate may need to be modified for this production system, particularly
under irrigated conditions. Field experiments will be conducted to evaluate the interaction of
irrigation, row configuration, seeding rate, and nitrogen rate on grain sorghum plant development
and yield.

        A field experiment was conducted in 2009 on Sharkey clay at Northeast Research Station
(NERS) to evaluate the influence of irrigation, row configuration, seeding rate, and nitrogen rate
on yield of grain sorghum. Two irrigation treatments, a non-irrigated control and a furrow-
irrigated treatment scheduled whenever the soil moisture deficit reaches 2-inches using the
Arkansas Irrigation Scheduler, was evaluated. Row configurations were single and twin rows
centered, 9.5-inches apart, on raised beds. Four 16-inch rows were also planted on 80-inch wide
raised beds. Seeding rates were 4, 6, 8, and 10 seed/ft on single row and equivalent seeding rates
on twin rows and wide beds. Nitrogen rates were 120 and 150 lb/acre broadcast as urea (with
Agratain®). Single rows were planted with a JD 1700 and twin rows with a Monosem twin-row
planter. Wide beds were planted with a JD 2100 cone planter configured with four planting units
spaced 16-inches apart. Similar studies comparing single and twin rows were conducted on
Gigger silt laom at the Macon Ridge Research Station in Winnsboro. Measurements will include
yield and yield components (number of heads/acre, seed weight, and seed/head).
                                          Results and Discussion
        The trial at St. Joseph had extremely low yields, which was due in part to a relatively late
planting date (May 8), a wet July (7.1 inches), and severe midge damage. An application of a
pyrethroid was applied in early July for the control of midge but additional applications were not
made. The data below is from the irrigated trial. There was a difference in row configurations
with both the twin row and 16-inch rows on wide bed having higher yields than the single row.
However, these results were confounded by the midge damage, with the single row treatment
having more severe midge damage than the other two row configuration treatments.
A complimentary study was conducted on a Gigger silt loam in Winnsboro. Nitrogen rate and the
wide bed were not evaluated in this study. This trial was also planted late (May 19) but timely
rains in July produced good yield on this dryland soil. Seeding rate did not affect yield; however,
there was a difference in yield between the single row and twin row planting systems. Average
yields were 5322 lb/acre for the single row and 542 lb/acre for the twin row. These findings are
not very conclusive because of weather and insect damage, particularly at St. Joseph. Additional
studies will better define optimum management practices that will maximize grain sorghum yield
and profitability.

Table 1. Influence of seeding and N rate on grain sorghum yield on single row, twin row, and
wide bed on Sharkey clay in St. Joseph, 2009.
 rate1                   N rate           Single row               Twin row              Wide bed
                         lb/acre      ------------------------------lb/acre-----------------------------

    1                       120                  1399                  1781                 1848
                            150                  1421                  1670                 2337

    2                       120                  1572                  1865                 1997
                            150                  1403                  1932                 2333

    3                       120                  1434                  2010                 2201
                            150                  1295                  1798                 2141

    4                       120                  1637                  2110                 1948
                            150                  1315                  1690                 1565

 Average                                      1435                  1858                 2042
 The seeding rates of 1, 2, 3, and 4 were equivalent to 4, 6, 8, and 10 seed/ft for single row and 2,
3, 4, and 5 seed/ft for twin row and 16-inch rows on wide bed.
Table 2. Influence of seeding rate on grain sorghum yield on single and twin row on Gigger silt
loam in Winnsboro, 2009.
 Seeding rate1                               Single row                             Twin row

    1                                             4991                                 5572
    2                                             5553                                 5615
    3                                             5276                                 5551
    4                                             5470                                 5432

    Average                                       5322                                 5542

 LSD (0.10)                                                     175
 The seeding rates of 1, 2, 3, and 4 were equivalent to 4, 6, 8, and 10 seed/ft for single row and
2, 3, 4, and 5 seed/ft for twin row.

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