J.J. Heitholt, Texas Agric. Exp. Stn., Dallas, TX

J.J. Farr, Texas Agric. Exp. Stn., Dallas, TX

D. Kee, Texas Coop. Extension, Commerce, TX

J.C. Read, Texas Agric. Exp. Stn., Dallas, TX

S. Metz, Texas Agric. Exp. Stn., Dallas, TX

C.T. MacKown, USDA-ARS, El Reno, OK

Abstract:

Effective management of soybean grown in north-central Texas requires knowledge of the potential value as a forage and a grain crop.  To better understand these uses, two soybean cultivars (Tyrone and Deltapine DP 5110S) were planted in 14-inch and 28-inch rows on 11 May 2001 near Dallas,TX. The soil was a Houston Black Clay with pH 8.3. Plots were harvested for forage on 16 July and 9 Aug using a mechanical forage plot harvester. Growth stages were R3 and R6 for DP 5110S and R1 and R3 for Tyrone. Plots were harvested for grain on 24 September (DP 5110S) and 24 October (Tyrone). Forage and grain yields were similar between row spacings but slightly greater with DP 5110S. Forage yields averaged 1.58 tons/acre at the first harvest and 2.01 tons/acre at the second harvest. The cultivar DP5110S had lower acid detergent fiber (ADF) and neutral detergent fiber (NDF) at the first harvest and higher N concentration at the second harvest than Tyrone. In vitro dry matter digestibility (IVDMD) was similar across cultivars, row spacings, and harvests. By the second harvest DP 5110S had a greater percentage of biomass in fruit than Tyrone (13% vs. 1%) and Tyrone had a greater percentage in leaves (34% vs. 28%). Plate meter readings corresponded well to biomass within a harvest.  However, similar values were obtained in the second harvest compared to the first harvest even though much more biomass existed in the second harvest. Because of low grain yields (<18 bu/a) and low grain prices, harvesting either cultivar for forage would likely be more profitable than harvesting for grain in this situation.

Acknowledgment: We thank Doug Pustejovsky of Deltapine Seeds and Dan Ryan, Frontier Hybrids for supplying seed.

Introduction

Drought in east Texas during soybean grain maturation often leads to crop failure. One alternative to low grain production and lost income would be to harvest the crop for hay. In order to better understand the value of soybean as a hay crop we need to study the effects of cultivar and production practices on soybean forage yield.

Experimental Procedures

The soybean forage study was conducted in Dallas, TX. Soil type was a Houston Black Clay with pH 8.2.   On 11 May 2001, two soybean cultivars were planted, Tyrone (a late maturing forage variety) and DP5110S (a mid maturity grain variety). Two row spacings were used, 14-inch and 28-inch and there were three replicates. Plots with 14-inch rows were 12 rows wide and those with 28-inch rows were 6 rows wide; all plots were 25 feet long. Seeding rate was 200,000 plants per acre and seed were inoculated with Cell-Tech 2000 prior to planting. The herbicides,  Dual (1.5 pint/acre) and Scepter 70G (1.4 oz/acre) were applied immediately after planting on the afternoon of 11 May 2001.  During the season, plant height and plate meter readings were taken. The plate meter is a plywood device (14.5 inches by 24 inches) that is placed on the soybean canopy that is used to estimate forage yield. Compression of the plant canopy by the plate meter is calibrated for aboveground biomass.  The reading (in cm) represents the height to which the plate is held above the ground by its plate. Plots were end-trimmed to 16 feet and the total above ground forage from the four center rows of plots with 14-inch rows and the two center rows of the plots with 28-inch rows were harvested on 16 July and 9 Aug. The forage was harvested with a mechanical forage harvester and weighed automatically in the field. Sub samples were collected, dried, and measured for moisture, and then ground for IVDMD, NDF, ADF, and total N analysis.

In addition to the mechanical harvests, hand harvests of 0.215m² (narrow rows) and 0.430 m² (wide rows) were obtained performed to determine dry matter distribution. Plate meter readings were collected also on these small areas in order to compare biomass to plate meter readings. Plots (15 feet ´ 5 feet) were harvested for grain on 24 September (DP 5110S) and 24 October (Tyrone).

Results and Discussion

Forage yields were similar between row spacings but DP5110S produced more forage than Tyrone (Table 1). Forage yields averaged 1.58 tons/acre at the first harvest and 2.01 tons/acre at the second harvest. The cultivar DP5110S had lower acid detergent fiber (ADF) and neutral detergent fiber (NDF) at the first harvest and higher N concentration at the second harvest than Tyrone (Table 2). In vitro dry matter digestibility (IVDMD) was similar across cutivars, row spacings, and harvests. Concentrations of N and total N produced per acre (Table 3) were unexpectedly lower in all samples than concentrations seen in previous studies. Plate meter readings corresponded well to biomass within a harvest (Table 4).  However, plate meter readings did not increase much between harvest 1 and harvest 2 but hay yields did. By the second harvest DP 5110S had a greater percentage of biomass in fruit than Tyrone (13% vs. 1%) and Tyrone had a greater percentage in leaves (34% vs. 28%) (Table 5). Grain yields per acre were all under 20 bu/a (Table 6) indicating that the value of hay production would have been more than the value of grain if price for grain was $4.20 per bushel and price for hay was $40 per ton.

Table Legends:

Table 1. Forage biomass of two soybean cultivars at two row spacings in Texas in 2001.

Table 2. Forage nutrient quality of two soybean cultivars grown at Dallas in 2001.

Table 3. Soybean Plate Meter – Biomass data from hand harvests taken in coordination with mechanical harvests in 2001.

Table 4. Dry matter distribution of two soybean cultivars averaged across row spacings.

Table 5. Forage nitrogen concentration, forage yield, and N yield per acre of two soybean cultivars in Texas in 2001.

Table 6. Grain yields of two soybean cultivars as affected by row spacing.
 

Table 1. Forage biomass of two soybean cultivars at two row spacings in Texas in 2001.
 

Date	Cultivar	Row Spacing	Dry Matter (tons/acre)
16 July	DP5110S	14	1.58
		28	1.67
		Ave.	1.62*
	Tyrone	14	1.51
		28	1.58
		Ave.	1.54
LSD(0.05) Cultivar ´ Row Spacing			0.07
9 Aug	DP5110S	14	2.01
		28	2.14
		Ave.	2.07*
	Tyrone	14	2.05
		28	1.88
		Ave.	1.96
LSD(0.05) Cultivar ´ Row Spacing			0.07

*Indicates that DP5110S was significantly (P<0.05) greater than Tyrone.

Table 2. Forage Nutrient Quality of Two Soybean Cultivars Grown at Dallas in 2001.
 

Date	Cultivar	Row Spacing	%N	%NDF	%ADF	%IVDMD
16 July	DP5110S	14	1.82	44.6	30.5	73.9
		28	1.92	47.2	32.4	70.7
		Avg.	1.87	45.9	31.4	72.3
	Tyrone	14	1.77	48.2	33.2	70.4
		28	1.72	48.5	33.6	70.1
		Avg.	1.74	48.9	33.4	70.2
LSD(0.05) Cultivar			ns	1.1	1.2	1.1
LSD(0.05) C ´ RS				1.6	1.8	1.5
Cultivar			ns	*	*	*
Row Spacing			ns	ns	ns	*
Cultivar ´ Row Spacing			ns	ns	ns	*
9 Aug	DP5110S	14	1.47	45.3	30.5	71.5
		28	1.60	48.9	32.3	69.2
		Avg.	1.54	47.1	31.4	70.4
	Tyrone	14	1.42	47.0	31.9	70.8
		28	1.39	46.0	32.2	71.5
		Avg.	1.41	46.5	32.1	71.1
LSD(0.05) C ´ RS			0.07	1.9	ns	ns
Cultivar			**	ns	ns	ns
Row Spacing			ns	ns	ns	ns
Cultivar ´ Row Spacing			*	*	ns	ns

*,** Indicates effects were significantly different at the 5% and 1% level, respectively.
 

Table 3. Forage nitrogen concentration, forage yield, and N yield per acre of two soybean cultivars in Texas in 2001.

Cultivar	Row Spacing	% N	g/m2	Tons/acre	Total N per acre (lbs)
DP5110S	14	1.82	353	1.58	57.5
	28	1.92	374	1.67	64.1
	Avg.	1.87	364	1.62	60.6
Tyrone	14	1.77	339	1.51	53.4
	28	1.72	354	1.58	54.3
	Avg.	1.74	346	1.54	53.6
LSD(0.05)		ns	ns	0.07	ns

Cultivar	Row Spacing	% N	g/m2	Tons/acre	Total N per acre (lbs)
DP5110S	14	1.47	451	2.01	59.1
	28	1.60	478	2.14	68.5
	Avg.	1.54	464	2.07	63.7
Tyrone	14	1.42	459	2.05	58.2
	28	1.39	422	1.88	52.3
	Avg.	1.41	440	1.96	55.3
LSD(0.05)		0.07	ns	ns	ns

 
 
 
 

Table 4. Soybean plate meter biomass data from hand harvests taken in coordination with mechanical harvests in 2001.
 

Cultivar	Row Spacing	Parallel Plate#	Perpendicular Plate	Plant Height (cm)	Hand Harvest (tons/acre)	Machine Harvest (tons/acre)
July
DP5110S	14	47	-	66	1.73	1.58
DP5110S	28	69	-	79*	1.93	1.67
Tyrone	14	59	-	68	1.92	1.51
Tyrone	28	75	-	79*	1.90	1.58
LSD (0.05) July		9	-	17	ns	0.07
August
DP5110S	14	65	60*	79	2.57	2.01
DP5110S	28	62	58*	80	2.57	2.14
Tyrone	14	73	70*	77	2.97	2.05
Tyrone	28	76	78*	79	2.35	1.88
LSD (0.05) Aug.		10	12	ns	0.26	0.07

Area harvested 0.60 m of row.

This represented 0.215m² for narrow rows (14-inch) and 0.430m² for wide rows (28-inch).

Length of plate meter = 60.5 cm.

Harvest dates in July were 10, 11, and 13 for reps 1, 2, and 3 respectively.

Harvest dates in August were 6, 8, and 10 for reps 1, 2, and 3 respectively.

* Indicates significant differences across cultivars.

# Parallel Plate, long dimension of the plate held in the row direction
   Perpendicular Plate, long dimension of the plate held perpendicular to the row

Table 5. Dry matter distribution of two soybean cultivars averaged across row spacings from soybean grown in Dallas in 2001.

Plate meter was placed parallel to row (directly on top of row);

row 3 for narrow, row 2 for wide.

Area for narrow rows = 0.215 m²

Area for wide rows = 0.430 m²

* Indicates cultivar significantly different with a sampling date (P<0.05).

Table 6. Soybean Grain Yields in Dallas in 2001.