Twain J. Butler

Estimation of biomass and canopy height in bermudagrass, alfalfa, and wheat using ultrasonic, laser, and spectral sensors.

Non-destructive biomass estimation of vegetation has been performed via remote sensing as well as physical measurements. An effective method for estimating biomass must have accuracy comparable to the accepted standard of destructive removal. Estimation or measurement of height is commonly employed to create a relationship between height and mass. This study examined several types of ground-based mobile sensing strategies for forage biomass estimation. Forage production experiments consisting of alfalfa (Medicago sativa L.), bermudagrass [Cynodon dactylon (L.) Pers.], and wheat (Triticum aestivum L.) were employed to examine sensor biomass estimation (laser, ultrasonic, and spectral) as compared to physical measurements (plate meter and meter stick) and the traditional harvest method (clipping). Predictive models were constructed via partial least squares regression and modeled estimates were compared to the physically measured biomass. Least significant difference separated mean estimates were examined to evaluate differences in the physical measurements and sensor estimates for canopy height and biomass. Differences between methods were minimal (average percent error of 11.2% for difference between predicted values versus machine and quadrat harvested biomass values (1.64 and 4.91 t·ha−1, respectively), except at the lowest measured biomass (average percent error of 89% for harvester and quad harvested biomass < 0.79 t·ha−1) and greatest measured biomass (average percent error of 18% for harvester and quad harvested biomass >6.4 t·ha−1). These data suggest that using mobile sensor-based biomass estimation models could be an effective alternative to the traditional clipping method for rapid, accurate in-field biomass estimation.

Coastal Bermudagrass (Cynodon dactylon) Yield Response to Various Herbicides

Several new herbicides have been registered for pasture weed control, but their effect on ‘Coastal’ bermudagrass dry matter (DM) yield has not been documented. The objective of this study was to determine the effect of clopyralid, fluroxypyr, imazapic, picloram, picloram + fluroxypyr, picloram + 2,4-D amine, triasulfuron + dicamba, triclopyr amine + clopyralid, triclopyr ester, triclopyr ester + fluroxypyr, trifloxysulfuron, 2,4-D amine + dicamba, and 2,4-D ester on Coastal bermudagrass yield. Total DM yields of Coastal bermudagrass were not reduced by 0.84 kg/ha clopyralid, 0.031 kg ai/ha triasulfuron + 0.44 kg ai/ha dicamba, 1.205 kg ai/kg 2,4-D amine + 0.42 kg/ha dicamba, and 2.31 kg/ha 2,4-D ester. Although 0.227 kg ai/ha picloram + 0.84 kg/ha 2,4-D amine, 0.945 kg ai/ha triclopyr amine + 0.315 kg ai/ha clopyralid, and 1.68 kg ai/ha triclopyr ester reduced Coastal bermudagrass DM yields in harvest 1, there was no cumulative loss in total production in either 2001 or 2002 with these herbicides compared with that of the nontreated control. Coastal bermudagrass total DM yields were reduced by 52% with 0.158 kg ai/ha imazapic when applied to dormant bermudagrass in 2001, and by 26% with 0.021 kg ai/ha trifloxysulfuron when applied to actively growing bermudagrass in 2001; however, neither herbicide reduced total cumulative yield in 2002. In 2001 and 2002, total DM yield was reduced by an average of 25% with 0.42 kg/ha fluroxypyr, by 45% with 0.105 kg/ha imazapic, by 57% with 0.158 kg/ha imazapic, by 65% with 0.21 kg/ha imazapic, by 25% with 0.56 kg/ha picloram, by 20% with 0.188 kg/ha picloram + 0.188 kg/ha fluroxypyr, and by 18% with 0.63 kg/ha triclopyr ester + 0.21 kg/ha fluroxypyr, when applied to actively growing Coastal bermudagrass. Nomenclature: Clopyralid; dicamba; fluroxypyr; imazapic; picloram; triasulfuron; triclopyr amine; triclopyr ester; trifloxysulfuron; 2,4-D amine; 2,4-D ester; bermudagrass, Cynodon dactylon (L) Pers. ‘Coastal’ #3 CYNDA. Additional index words: Bermudagrass tolerance, injury, yield.

Dairy manure compost quality effects on corn silage and soil properties.

Soil nutrients in dairy manure composts vary depending on the original manure or other additives, with consequent effects on crop production. An experiment addressing the effects of single applications of dairy compost of high quality (HQC) or low quality (LQC) at the incorporation rates of 0, 45, and 90 Mg ha−1 on corn (Zea mays L.) silage yields, forage quality, and soil nutrients was conducted in 2004 and 2005. The composts were incorporated prior to planting in 2004, which were also compared with the performance of two commercial fertilizer levels (N-P-K) at high (HIF, 336-98-93) or low rates (LIF, 168-49-47). Compost treatment plots received annual split applications of supplemental inorganic N at 224 or 336 kg ha−1. Through the two growing seasons, corn silage yields ranged from 17 to 25 Mg ha−1 yr−1 depending on compost quality and compost application rates. Corn silage yields in plots with HQC were generally greater than LQC in 2004, but yields did not differ in 2005. Total apparent N recovery did not differ between compost qualities or among compost rates. Soil pH of LQC treatments averaged 8.1 after the second season and remained higher than that of HQC which ranged from 7.4 to 7.6. Electrical conductivity (EC) of soils from HQC plots was 14% lower than that of LQC in 2004 and became similar to that of LQC in 2005. Soil P and K levels in LQC were greater than HQC and were greatest in the 90 Mg ha−1 rate. Based on these data, there is no advantage of using the higher quality compost with greater OM.

Phosphorus Fertilization of Annual Ryegrass and Comparison of Soil Phosphorus Extractants

ABSTRACT It is unclear how much phosphorus (P) fertilizer is needed to maximize annual ryegrass (Lolium multiflorum Lam.cv. ‘TAM90’) forage yield and nutritive value in lower-rainfall climates. It is equally unclear which soil-P extractant is most effective when making P fertilization decisions. A 3-yr field study addressed these issues using small replicated plots during the winter months in north-central Texas. The addition of P increased yields every year of the trial, but optimum levels depended on rainfall distribution: 19 kg P ha− 1 yr− 1 was optimum two years, while 28 kg P ha− 1 yr− 1 increased yields 51% the year with good mid-season moisture. The addition of P fertilizer did not increase forage crude protein or affect fiber concentrations but did increase P yields. Percent relative yield of ryegrass was correlated with Mehlich III soil test P, soil pH, and P application rate. Conversely, the acidified NH4OAc-EDTA soil P extractant failed to relate to percent relative yield.

Broomsedge (Andropogon virginicus) Response to Herbicides and Burning1

Broomsedge control studies were conducted on six broomsedge-infested pastures in southeastern Oklahoma from 1995 to 1997. Glyphosate applied in spring at 2.24 kg ai/ha decreased broomsedge plant density by 58% 3 mo after treatment (MAT), on areas where the previous years forage was grazed, and by 95% 3 MAT, where spring fire had removed the old top-growth before glyphosate application. Broomsedge plant density was not affected where glyphosate was applied in spring to sites with old-standing top-growth. Paraquat applied in spring at 0.56 kg ai/ha and spring burning without a herbicide treatment had no effect on broomsedge plant density. Glyphosate at 0.56 and 1.12 kg ai/ha applied in late summer reduced the number of broomsedge stems 1 yr after treatment (YAT) by an average of 65 and 80%, respectively. Paraquat at 0.56 kg/ha applied in late summer of 1995, followed by burning 1 wk after treatment (WAT), decreased broomsedge stem density by more than 60% 1 YAT at four of six locations when compared with mowing in late summer. Burning in November after an October frost decreased broomsedge stem density by more than 47% 1 YAT at four locations. Two consecutive years of burning after frost and paraquat applied in late summer followed by burning 1 WAT reduced broomsedge dry matter production by 68 and 96%, respectively, when compared with mowing in late summer. These data suggest that good to excellent control of established broomsedge is possible with herbicides alone, with a combination of herbicides and late-summer burning, and with fall burning after an early frost in a dry fall. However, broomsedge control was short-lived with all the treatments because of the establishment of new broomsedge seedlings. Thus, it will be important to integrate the destruction of broomsedge plants with proper fertility and grazing management in order to provide satisfactory broomsedge control. Nomenclature: Glyphosate; paraquat; broomsedge, Andropogon virginicus L. #3 ANOVI. Additional index words: CYNDA, Cynodon dactylon, mowing, prescribed fire. Abbreviations: DM, dry matter; MAT, months after treatment; WAT, weeks after treatment; YAT, years after treatment.

Response of Coastal Bermudagrass (Cynodon dactylon) to Various Herbicides and Weed Control during Establishment1

Field experiments were conducted to determine the effects of application timings and various herbicides on newly established ‘Coastal’ bermudagrass in 2001, 2002, and 2003. The experimental design was a split plot with three replications. Main plots consisted of three herbicide application timings of 1, 14, and 28 d after planting (DAP), and the subplots were 16 herbicide treatments. The hormone herbicides (picloram at 0.19 kg ae/ha + fluroxypyr at 0.19 kg ae/ha, picloram at 0.08 kg/ha + 2,4-D amine at 0.28 kg ae/ha, picloram at 0.15 kg/ha + 2,4-D amine at 0.56 kg/ha, 2,4-D amine at 2.2 kg/ha, 2,4-D amine at 1.2 kg/ha + dicamba at 0.42 kg ae/ha, and 2,4-D ester at 2.3 kg ae/ha) applied 1 DAP controlled large crabgrass 55 to 85%, did not injure Coastal bermudagrass sprigs, and aided establishment resulting in 22 to 27% ground cover in 2001 and 25 to 42% ground cover in 2002. Imazapic at 0.02, 0.035, and 0.05 kg ai/ha applied 1 and 14 DAP injured Coastal bermudagrass 5 to 45% across years, yet these plots had 20 to 54% ground cover compared with only 3 to 7% ground cover in the nontreated area in 2001, 2002, and 2003. The reduced rate of glyphosate (0.21 kg ae/ha) injured Coastal bermudagrass less than 8% and controlled large crabgrass 86 to 90% when applied 14 DAP, resulting in 43, 25, and 18% ground cover in 2001, 2002, and 2003, respectively. Trifloxysulfuron at 0.02 kg ai/ha applied 1 and 14 DAP did not injure Coastal bermudagrass sprigs, controlled junglerice 90%, and resulted in 73 and 52% ground cover, respectively. Coastal bermudagrass establishment was greatly increased when weeds were controlled. Nomenclature: 2,4-D amine, 2,4-D ester, dicamba, fluroxypyr, glyphosate, imazapic, picloram, trifloxysulfuron, bermudagrass, Cynodon dactylon (L.) Pers. ‘Coastal’, junglerice, Echinochloa colona (L.) Link #3 ECHCO, large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA. Additional index words: Bermudagrass sprigs, establishment, injury, phytotoxicity. Abbreviations: ai, active ingredient; ae, acid equivalent; DAT, days after treatment; NIS, nonionic surfactant.