K.Dillon, Virginia Tech
VIRGINIA SOYBEAN BOARD PROJECT PROPOSAL – FY2013/2014
ONE-PAGE SUMMARY
PROJECT NAME: Optimization of Early-Season Vegetative Growth and Seed Yield of Double-Crop Soybean Systems
TERM OF PROJECT: July 1, 2013 to June 30, 2014
COOPERATORS: David L. Holshouser, Assoc. Professor & Extension Agronomist
Kevin A. Dillon, Graduate Research Assistant
LOCATION: Virginia Tech – Tidewater Agricultural Research and Extension Center
6321 Holland Road
Suffolk, VA 23437
Telephone: (757) 657-6450 ext. 412
Mobile: 757-355-2972 (D. Holshouser) or 252-560-7591 (K. Dillon)
Email: or
TOTAL COST OF PROJECT: $70,500
FUNDS REQUESTED: $45,500 (65% of total project cost)
PROJECT OBJECTIVES:
1. Evaluate seeding rate, seed-applied inoculant, starter N applied at planting, cultivar growth habit, and foliar fungicide application on soybean vegetative response and seed yield in a wheat-soybean double-crop system in the Mid-Atlantic region.
2. Evaluate soybean vegetative growth response and seed yield with starter N at planting with or without seed-applied Bradyrhizobia japonicum inoculant in a wheat-soybean double-crop system.
3. Evaluate the response and specific interaction between soybean cultivars and foliar fungicide application in a wheat-soybean double-crop system.
EXPECTED RESULTS:
Critical agriculture inputs within the Virginia wheat-soybean double-crop system will be identified. Soybean yield and quality will be increased and maintained at high levels with the use of specific inputs. Having plant-available nitrogen at planting for soybean uptake will be critical for early-season growth. Nitrogen fixation dynamics will be affected greatly by excess nitrogen application. Soybean varieties will differ in their interaction between foliar fungicide application timings. Seed yield increase from fungicide use will be observed but will depend greatly on variety, disease incidence, and growing environment.
ESTIMATED WORTH:
This research will demonstrate that through the manipulation of specific agronomic inputs, early vegetative growth and yield of double-crop soybean can be economically increased while sustainably improving the wheat-soybean double-crop system. Results should increase our understanding of how different maturity group IV and V soybean varieties interact with foliar fungicide application timings. Mid- to late-season soybean disease patterns across Virginia will be examined in great detail through this research. We will increase understanding of soybean nutrition and plant disease and how they specifically influence soybean production. Conclusions made from research finding will assist Virginia soybean farmers in making better agronomic decisions and increasing profit.
PROJECT PROPOSAL
TO
THE VIRGINIA SOYBEAN BOARD
Title: Optimization of Early-Season Vegetative Growth and Seed Yield
of Double-Crop Soybean Systems
Cooperators: David L. Holshouser, Assoc. Professor & Extension Agronomist
Kevin A. Dillon, Graduate Research Assistant
Virginia Tech – Tidewater AREC
6321 Holland Road
Suffolk, VA 23437
(757) 657-6450 ext. 412
Mobile: 757-355-2972 (D. Holshouser) 252 - 560-7591 (K. Dillon)
Email:
Duration of Request: July 1, 2013 to June 30, 2014
Total Cost of Project: $70,500
Funds Requested: $45,500 (65% of total project cost)
Goals and Objectives:
The goal of the research is to determine management practices and inputs that maximize early vegetative growth and seed yield, while optimizing double-crop wheat-soybean production system profitability. Specific research objectives for the 2013 growing season are listed below.
1. Evaluate seeding rate, seed-applied inoculant, starter N applied at planting, cultivar growth habit, and foliar fungicide application on soybean vegetative response and seed yield produced in a wheat-soybean double-crop system in the Mid-Atlantic region.
2. Evaluate soybean vegetative growth response and seed yield with starter N at planting with or without seed-applied Bradyrhizobia japonicum inoculant in a wheat-soybean double-crop system.
3. Evaluate the response and specific interaction between soybean cultivars and foliar fungicide application in a wheat-soybean double-crop system.
Project Significance:
Soybean [Glycine max (L.) Merr.] and winter wheat (Triticum aestivum L.) production is crucial to the U.S. and Virginia’s agricultural industry. Soybean accounts for 90% of the U.S. annual oilseed production and is therefore considered the most economically important oilseed crop grown in America (Ash, 2010). During 2012, approximately 75.7 million acres (ac) soybean were harvested and over 2.9 billion bushels (bu) produced; this U.S. production was valued at $42.2 billion with 37.8 bu ac-1 observed mean yield and $14.56 per bu market price (2012 mean) (NASS, 2013). Winter wheat production in 2012 in the U.S. accounted for 41.3 million ac planted, 34.8 million ac harvested, and 1.6 billion bu grown; this production resulted in $13.2 billion value, with $8.00 per bu market price (2012 mean) (NASS, 2013). National winter wheat yields averaged 47.2bu/ac in 2012 and acres are projected to increase in 2013 with 41.8 million ac planted (NASS, 2013).
The Mid-Atlantic region of the U.S., which includes the states Delaware, Maryland, New Jersey, North Carolina, Pennsylvania, and Virginia, accounted for 3.4 million ac soybean and 1.7 million ac winter wheat in 2012 (NASS, 2013). When the regional acreage was broken down by state, the following estimates were reported: North Carolina (1.6 million ac soybean and 830,000 ac winter wheat), Virginia (590,000 ac soybean and 280,000 ac winter wheat), Pennsylvania (530,000 ac soybean and 165,000 ac winter wheat), Maryland (480,000 ac soybean and 310,000 ac winter wheat), New Jersey (95,000 soybean and 33,000 ac winter wheat), and Delaware (170,000 ac soybean and 85,000 ac winter wheat) (NASS, 2013). Virginia’s 590,000 ac soybean planted in 2012 resulted in 580,000 ac harvested, 42 bu/ac average yield, 24.4 million bu produced, and production valued at $355 million (NASS, 2013). During that same year, Virginia harvested 240,000 ac of winter wheat that averaged 65 bu ac-1 and resulted in 15.6 million bu with $124.8 million total value (NASS, 2013). National Ag Statistics Service (2013) estimated that 290,000 ac winter wheat were planted in Virginia in fall 2012.
Producers utilize the wheat-soybean double-crop system in Virginia to maximize land use and profitability. Even with the increased production value of both soybean and winter wheat, there is an increased risk level associated with double-crop soybean after wheat. This observed increase in risk is due in large part to delayed planting in the summer, reduced soil moisture and plant-available water, lower plant-available nutrient levels due to wheat uptake, higher air and soil temperatures coinciding with critical growth stages, increased plant residue, and the increased disease, insect, and weed pressure during pod and seed development. Due to the aforementioned production issue, double-crop soybean yields are usually less than full-season soybean yields.
Background, Prior and Current Research, and Extension Efforts:
Mono-crop and Double-crop Systems
Mono-crop, produced during a long growing season is inefficient when compared to multiple cropping, which was widely adopted in differing environments (Egli, 2011). Compared to mono-crop, double-crop more efficiently captures precipitation and photosynthetically active radiation and increases the productivity of the growing environment through the addition of crop residues to the soil, which benefits soil quality and provides additional sink for atmospheric CO2 (Caviglia and Andrade, 2010; Caviglia et al., 2004, 2011). Crop rotations involving small grains improved weed management, eliminated the need for tillage, increased water infiltration and soil organic matter, improved soil structure, trapped excess nitrogen (N), and reduced soil erosion from surface water runoff (Bernstein et al., 2011; Hartwig and Ammon, 2002; Kaspar et al., 2001; McMaster et al., 2000; Ruffo et al., 2004; Savabi and Stott, 1994). Multiple cropping increases productivity by increasing the time year-1 devoted to seed filling by multiple seed fill periods (Egli, 2011). Wheat-soybean double-crop systems in Oklahoma, Kansas, and Mississippi have demonstrated increased net returns as compared to mono-crop soybean (Farno et al., 2002; Kelley, 2003; Kyei-Boahen and Zhang, 2006, respectively).
Agronomic soybean yield potential is reduced as planting date is delayed (Bastidas et al., 2008; Chen and Wiatrak, 2010; De Bruin and Pedersen, 2008; Egli and Cornelius, 2009). Research conducted in Ohio by Jeffers et al. (1973) and later by Beuerlein (2001) determined that for every week after June 15th that soybean planting is delayed, soybean loses up to 7 bu/ac per week. The use of a double-crop system results in soybean planting that is delayed past dates recommended for optimum yield potential (Taylor et al., 2005). Yield reduction for late-planted double-crop soybean was attributed to lack of sufficient vegetative growth (Ball et al., 2000b; Boerma et al., 1982; Caviglia et al., 2011; Herbert and Litchfield, 1984; Jones et al., 2003), reductions in crop growth rate during the period when seed number (Egli and Bruening, 2000) and seed weight (Calvino et al., 2003) are defined, and reproductive phase duration (Egli, 2011). Board and Hall (1984) indicated that premature flowering induced by short photoperiod is a major yield limiting factor in July plantings between 30° and 32° 30’ N latitude. Increasing yield in late-planted soybean was correlated to increasing leaf area that maximizes light interception and subsequently increases biomass (Board and Harville, 1993; Board et al., 1992; Jones et al., 2003; Wells, 1991). Jones et al. (2003) attributed yield loss in a double-crop wheat-soybean system, compared to full-season soybean, to decreased leaf area development and reduced amount of time to accumulate sufficient leaf area index (LAI) for maximum yield. The most influential factor on double-crop soybean LAI and seed yield was determined to be soil texture and associated plant-available water (Jones et al., 2003). Jones et al. (2003) recommended the implementation of increasing plant population and decreasing row spacing to increase LAI. Research demonstrated that higher plant populations were needed to maximize light interception and yield when soybean were planted past the optimum dates; these findings were especially crucial if drought stress limited leaf area production (Ball et al., 2000a; Holshouser and Whittaker, 2002). Holshouser and Whittaker (2002) observed early season intermittent drought to be common in the Mid-Atlantic region. Jones et al. (2003) also conducted soybean studies in Virginia and attributed reduced early season vegetative growth and leaf area development to moisture stress, especially on low plant-available water holding capacity soils.
Nitrogen Management in Soybean
Soybean have an extensive nutrient demand (Salvagiotti et al., 2009); as average yields increase, plant growth and seed yield may be limited by nutrients that were previously considered adequate. Sinclair and Horie, (1989) concluded that a large nitrogen (N) requirement associated with high yielding crops is due to N being an elemental component of proteins and enzymes that make up the photosynthetic components in leaves. Soybean yield is closely correlated with the N amount accumulated throughout the growing season and is determined by the pods retained by the plant and by N amount available during the bloom period (Lathwell and Evans, 1951). During the reproductive growth period, the soybean plant uses N from the soil residual pool (if any remains) and plant tissue; however biological N2 fixation rapidly decreases (Harper, 1987). Increases in N content in soybean seed were reported by Egli and Bruening (2007) and were attributed to N acquired during the seed-filling period rather than N mobilization from vegetative tissue. An association between effective filling period and seed N concentration was not observed; however Egli and Bruening (2007) emphasized not ruling out the link between seed N concentration and senescence without first examining high seed protein selection on total seed N requirement and total N available for reproductive growth through N uptake, fixation, and redistribution. Harper (1987) determined that the soybean compensates for the reduction in biological fixed N by utilizing plant tissue N, once R6 (full seed) is reached.
The N requirement for a 38 bu/ac seed yield was reported by Weber (1966) to be 192 lb N per acre; the International Plant Nutrition Institute (IPNI) (2011) determined the N requirement for 25, 40, 55, and 70 bu/ac seed yield to be 148, 224, 288, and 364 kg N per acre, respectively. This need for N is met by the residual soil N pool and with symbiotic N2 fixation from N fixing Rhizobia bacteria that convert N2 gas to plant available N (Beuerlein, 2004; Bezdicek et al., 1978; Bhangoo and Albritton, 1976; Patterson and LaRue, 1983). The Rhizobium bacterial strain responsible for N2 fixation in soybean is Bradyrhizobium japonicum. Soybean N demand can exceed 5 lb per bushel of seed for optimum yield (Flannery, 1986). Salvagiotti et al. (2008) determined that approximately 71 lb N ha-1 are required to produce biomass that contains 15 bushels of soybean seed and that 50 to 80% of this N requirement was met by N2 fixation. Lindemann and Glover (2003). Tien et al. (2002) reported that soybean can fix up to 250 lb N per acre through symbiotic N2 fixation; this accounted for 70% of the total plant N requirement.
Effective inoculation with Bradyrhizobia spp. bacteria is essential for N2 fixation and production of economic yield (Hiltbold et al., 1980). Biological N2 fixation does not function from the onset of vegetative growth (Wani et al., 1995), rather the Bradyrhizobia spp. bacteria actively start fixing N between V2 (second node)-V3 (third node) soybean growth stage. Bradyrhizobium japonicum populations were observed to be influenced by plant density, temperature, soil water content, organic matter, texture, and pH (Abendroth and Elmore, 2006; Albrecht et al., 1984; Bacanamwo and Purcell, 1999; Beuerlein, 2004; Graham, 1992; Seneviratne et al., 2000). Salvagiotti et al. (2008, 2009) reported that if N uptake is limited by an insufficient soil N supply or by declining biological N fixation during late seed fill, a less-than-optimal yield ceiling may be imposed upon the soybean crop. Due to the correlation of actively N fixing bacteria with an increase in yield, inoculum material containing Bradyrhizobia spp. bacteria were developed to apply as an in-furrow or on-seed treatment to increase N fixing efficiency. Inoculant use has become increasingly popular due to improved inoculant technology, relatively low product cost, ease of application, and increased input costs associated with nutrient management (De Bruin et al., 2010). When soybean are grown on a soil not previously grown with soybean, inoculation is recommended to ensure symbiotic N2 fixation and to encourage Bradyrhizobia spp. bacteria population establishment (De Bruin et al., 2010; Hiltbold et al., 1980; Schulz and Thelen, 2008). Inoculant should be applied if the field was flooded, has a non-optimal pH, is low in soil organic matter, or has a coarse textured soil (Abendroth and Elmore, 2006; Pedersen, 2004). Inoculation is a tool that can ensure proper nodulation and crucial N uptake within double-crop soybean plants.