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In the northern Great Plains (NGP), wheat is the primary grain commodity. There is a need for the NGP to have a detailed analysis of environmental impacts for wheat-based agricultural production systems to better understand regional agroecosystems. This article provides a cradle-to-field gate life cycle assessment (LCA) for NGP dryland wheat (Triticum aestivum L.) production. The environmental impacts for winter wheat production using crop rotation and agricultural intensification are quantified. Fourteen no-till crop rotations ranging in duration from 2 to 6 yr were evaluated and compared using data from a historical 13-yr replicated rotation study (>300 observations). Midpoint LCA categories chosen for this comparison are energy, agricultural land use, climate change potential, freshwater eutrophication, and freshwater ecotoxicity due to their direct links with agricultural management practices. The NGP farmers commonly use a fallow period every other year due to moisture limitations. This specific agricultural practice and allocations within rotations are critical considerations within agricultural LCAs. Two aspects of fallow considerations and a sensitivity analysis were also performed. The allocated midpoint impacts between crops in rotational studies averaged 0.31, 0.79, 0.62, and 0.63 kg CO2 eq. per unit of winter wheat when energy, economic, mass, and cereal unit allocations were used, respectively. Economic analysis of the studied experimental crop was performed; results demonstrated that crop insurance policies improved diversification economics by 20%. Agricultural diversification benefits and burdens were better represented by endpoint damage assessments than by midpoint impact analysis.

In semiarid dryland farming regions, No-till and intensified crop rotations may improve water use. Our objective was to determine water use efficiency (WUE) and precipitation use efficiency (PUE) for spring wheat (Triticum aestivum L.; SW) grown in crop sequences representing different levels of intensification, under minimum (Min-till) or No-till. Root zone (0–122 cm) water at planting (SWP) was 2.76 cm higher for two- and three-phase sequences under Min-till than continuous spring wheat (CSW), and sequences with fallow averaged 2.65 cm higher than those without. Conversely, SWP was unaffected by sequence under No-till, with less effect of fallow. Root zone water at harvest was unaffected by the number of crop phases or fallow under Min-till. However, values for CSW exceeded the two- or three-phase sequences by 1.57 and 2.53 cm under No-till, and sequences without fallow averaged 1.52 cm more than those with fallow. The highest WUE (8.4 kg grain ha⁻¹ mm⁻¹ water) was observed when SW was grown in three-phase sequences compared with 7.7 kg grain ha⁻¹ mm⁻¹ water, for CSW and SW-fallow. Spring wheat under Min-till had higher WUE in sequences with fallow, but no effects of fallow occurred with No-till. The lowest PUE (near 3 kg grain ha⁻¹ mm⁻¹ precipitation) and no effects of tillage were found in sequences with fallow. However, SW in continuously cropped sequences had PUE between 5.5 and 6.4 kg grain ha⁻¹ mm⁻¹ precipitation and was higher under No-till. Both WUE and PUE are affected by intensification but may also be influenced by patterns of weather.

Cover crops can serve as a valuable management tool for improving soil and water quality, but are an added expense for farmers. We evaluated the yields and economics of four cover crops and two winter fallow treatments in a spring wheat (Triticum aestivum L.)–soybean [Glycine max (L.) Merr.] rotation at three sites in Minnesota. The four cover crop treatments were winter rye (Secale cereal L.), forage radish (Raphanus sativus L.), winter camelina [Camelina sativa (L.) Crantz], and pennycress (Thlaspi arvense L.) planted into spring wheat stubble. The fallow treatments consisted of no-tilled and conventionally tilled soil. Radish winterkilled and rye was terminated chemically before planting soybean in early May. Soybean was inter-seeded between rows of camelina and pennycress at the same time it was planted in other treatments. Camelina and pennycress were harvested over soybean seedlings in late June. Camelina yields ranged from 600 to 1100 kg ha–¹, while pennycress ranged from 900 to 1550 kg ha–¹. Mono-cropped soybean averaged 1819, 3510, and 4180 kg ha–¹ in northern, central, and southern Minnesota, respectively. Soybean seedlings under oilseed cover crop canopies exhibited light-stress, which likely reduced soybean yield in these treatments by 22 to 30%. When oilseed and inter-seeded soybean yields were combined, total seed yields generally were equal to or exceeded those of mono-cropped soybean. In addition, net income for inter-seeded systems was typically equivalent to mono-cropped soybean. Improvements in net income are likely needed before the benefits of oilseed cover crops are fully realized.

Impacts of integrated crop–livestock (ICL) systems on water quality have not been well studied. Water quality parameters were quantified for two 30‐min rainfall simulations in wheat (Triticum aestivum L.)–cover crop, cover crop, and rangeland grass control phases of a long‐term ICL study site in Mandan, ND, in 2017 and 2018. Both pre‐graze and post‐graze simulations were conducted. Nitrate‐N (NO3−–N), nitrite‐N (NO2−–N), ammonia‐N (NH4+–N), phosphate‐P (PO43−–P), and total suspended solid (TSS) concentrations and loads were evaluated in surface runoff water, along with concentrations of NO3−–N, NO2−–N, NH4+–N, and PO43−–P in infiltration water. Non‐parametric ranked two‐way analysis of variance was used to evaluate differences for vegetation type and grazing as fixed effects, with year as a random effect. Surface runoff concentrations of NO3−–N and NH4+–N were significantly different with cover crop and wheat phases being greater than grass. A grazing effect was also observed with pre‐graze significantly greater than post graze for NO2−–N, NH4+–N, PO43−–P, and TSS surface runoff concentrations. For infiltration water concentrations, similar significant effects of vegetation type were observed for NO3−–N and PO43−–P, while pre‐graze was also greater than post‐graze for NO2−–N and PO43−–P. Due to variable runoff volumes, no significant differences were observed for loads of any parameters. Minimal runoff volumes (0–6.7 L) and significant vegetation and grazing effects in nutrient infiltration water concentrations highlight the importance of infiltration in such studies, particularly at sites in the northern Great Plains.

Integrated crop−livestock (ICL) system effects on soil organic carbon (SOC) and total nitrogen (TN) are highly variable due to differences in ecoregion‐specific management practices, historical land use, and inherent climatic/edaphic attributes. Few studies have evaluated ICL system effects on SOC and TN in semiarid regions, where soil attributes change slowly. This study quantified ICL system effects on SOC and TN in a long‐term experiment near Mandan, ND. Effects of three residue management treatments (Grazed, Removed, Control) on SOC and TN were determined at five depths (0−0.08, 0.08−0.15, 0.15−0.31, 0.31−0.61, and 0.61−0.91 m) in 1999 and 2014. No‐till practices were employed throughout the study following conversion of perennial grass pastures. A significance criterion of P ≤ .10 was used to assess treatment effects as the experimental design was constrained to two replications. Residue management affected SOC and TN in near‐surface depths only, with greater concentration of SOC and TN at 0−0.08 m under Grazed compared to Removed in 2014 (P = .0844 and .0576). When expressed on an equivalent mass basis, SOC stocks were greater under Grazed and Control compared to Removed. Soil organic C and TN stocks increased over time in the Control by 11.2 Mg C ha−1 and 1.2 Mg N ha−1, respectively (P = .0728 and .0868). Soil organic C stocks also increased over time under the Grazed treatment by 10 Mg C ha−1 (P = .0630). Study results highlighted the importance of residue retention and livestock grazing for increasing SOC and TN in ICL systems under semiarid conditions.

Understanding how agricultural management and climate change affect soil organic carbon (SOC) stocks is particularly important for dryland agriculture regions that have been losing SOC over time due to fallow and tillage practices, and it can lead to development of agricultural practice(s) that reduce the impact of climate change on crop production. The objectives of this study were: (i) to simulate SOC dynamics in the top 30 cm of soil during a 20-yr (1993-2012) field study using CQESTR, a process-based C model; (ii) to predict the impact of changes in management, crop production, and climate change from 2013 to 2032; and (iii) to identify the best dryland cropping systems to maintain or increase SOC stocks under projected climate change in central North Dakota. Intensifying crop rotations was predicted to have a greater impact on SOC stocks than tillage (minimum tillage [MT], no-till [NT]) during 2013 to 2032, as SOC was highly correlated to biomass input ( = 0.91, = 0.00053). Converting from a MT spring wheat (SW, L.)-fallow rotation to a NT continuous SW rotation increased annualized biomass additions by 2.77 Mg ha (82%) and SOC by 0.22 Mg C ha yr. Under the assumption that crop production will stay at the 1993 to 2012 average, climate change is predicted to have a minor impact on SOC (approximately -6.5%) relative to crop rotation management. The CQESTR model predicted that the addition of another SW or rye ( L.) crop would have a greater effect on SOC stocks (0- to 30-cm depth) than conversion from MT to NT or climate change from 2013 to 2032.

Conservation production systems are needed in the upper Midwest to slow soil and nutrient loss through tillage-induced erosion. However, producers are reluctant to adapt no-till strategies because of the cool-wet climate. With focus on strip-tillage (ST) and a diverse 4-yr (4y) crop rotation as alternatives to no-till, we assessed eight integrated strategies under both conventional (CNV) and organic (ORG) management. These included conventional moldboard plow + disk tillage (CT), with (YF) fertilizer or manure, with no (NF) amendments, and 2-yr (2y) rotations: ST-YF-4y, ST-NF-4y, ST-YF-2y, ST-NF-2y, CT-YF-4y, CT-NF-4y, CT-YF-2y, and CT-NF-2y. Temporal change and loss rates of total soil organic C (SOC) and N (SON) were measured using the equivalent soil mass method for the 0- to 30- and 0- to 60-cm profiles. Soil was sampled in autumn, after harvest and before tillage, in the first, second, sixth, and eighth years of rotation between 2002 and 2009. In 2002, management had no effect on baseline measurements. Average SOC and SON from 2002–2009 were significantly greater in YF strategy systems, with no other differences among strategies occurring. Net loss in SOC, but not SON, occurred over time, and estimated rates of loss were significant for all individual management strategies, but not all integrated strategies. Under CNV, estimated rates of loss were significant in all but the CNV-CT-NF-2y system. In contrast, under ORG, estimated rates of loss were significant only for ORG-CT-NF-4y and ORG-ST-NF-4y systems. Animal manure, particularly in combination with high residue inputs, had a positive impact for maintaining SOC.

Emphasis is placed on developing robust, productive, economically competitive, and environmentally benign agroecosystems. In 2012, after 18 yr of a study to evaluate the effects of crop sequence and tillage, we measured soil properties at various depths to 91.4 cm and estimated soil C. The experiment, near Mandan, ND, was a split-plot design, with crop sequence as whole plots and tillage (minimum tillage or no-till) as subplots. Crop sequences included continuous spring wheat (Triticum aestivum L.) with crop residue retained or removed, spring wheat–millet [Setaria italica (L.) Beauv.], spring wheat–safflower (Carthamus tinctorius L.)–fallow, spring wheat–safflower–rye (Secale cereale L.), and spring wheat–fallow. Soil organic C, calculated by the equivalent mass method (SOCem), was consistently higher (P < 0.001) than when calculated by the fixed-depth method. Disparities between the two methods, greatest near the soil surface, were attributable to tillage. Estimates of SOCem were not affected by cropping sequence at any depth, averaging about 26, 47, 73, 114, and 156 Mg ha-1 in the 0- to 7.6-, 0- to 15.2-, 0- to 30.5-, 0- to 61.0-, and 0- to 91.4-cm partitions. Tillage had no influence at depths

Interest from the US commercial aviation industry and commitments established by the US Navy and Air Force to use renewable fuels has spurred interest in identifying and developing crops for renewable aviation fuel. Concern regarding greenhouse gas emissions associated with land-use change and shifting land grown for food to feedstock production for fuel has encouraged the concept of intensifying current prominent cropping systems through various double cropping strategies. Camelina (Camelina sativa L.) and field pennycress (Thlaspi arvense L.) are two winter oilseed crops that could potentially be integrated into the corn (Zea mays L.)–soybean [(Glycine max (L.) Merr.] cropping system, which is the prominent cropping system in the US Corn Belt. In addition to providing a feedstock for renewable aviation fuel production, integrating these crops into corn–soybean cropping systems could also potentially provide a range of ecosystem services. Some of these include soil protection from wind and water erosion, soil organic C (SOC) sequestration, water quality improvement through nitrate reduction, and a food source for pollinators. However, integration of these crops into corn–soybean cropping systems also carries possible limitations, such as potential yield reductions of the subsequent soybean crop. This review identifies and discusses some of the key benefits and constraints of integrating camelina or field pennycress into corn–soybean cropping systems and identifies generalized areas for potential adoption in the US Corn Belt.

Cover crops can expand ecosystem services, though sound management recommendations for their use within semiarid cropping systems is currently constrained by a lack of information. This study was conducted to determine agroecosystem responses to late-summer seeded cover crops under no-till management, with particular emphasis on soil attributes. Short-term effects of late-summer seeded cover crops on soil water, available N, near-surface soil quality, and residue cover were investigated during three consecutive years on the Area IV Soil Conservation Districts Research Farm near Mandan, ND. Mean aboveground cover crop biomass was highly variable across years (1430, 96, and 937 kg ha–¹ in 2008, 2009, and 2010, respectively), and was strongly affected by precipitation received within 14 d following cover crop seeding. During years with appreciable biomass production (2008 and 2010), cover crops significantly reduced available N in the 0.9-m depth the following spring (P = 0.0291 and 0.0464, respectively). Cover crop effects on soil water were subtle, and no differences in soil water were found between cover crop treatments and a no cover crop control before seeding cash crops the following spring. Late-summer seeded cover crops did not affect near-surface soil properties or soil coverage by residue. Soil responses to late-summer seeded cover crops did not differ between cover crop mixtures and monocultures. Late-summer seeded cover crops may enhance ecosystem services provided by semiarid cropping systems through biomass production and N conservation, though achieving these benefits in a consistent manner appears dependent on timely precipitation following cover crop seeding.

Sustainably balancing biofuel crop production with food, feed, and fiber on agricultural lands will require developing new cropping strategies. Double- and/or relay-cropping winter camelina (Camelina sativa L.) with soybean [Glycine max (L.) Merr.] may be a means to produce an energy and food crop on the same land in a single year. A study was conducted between 2009 and 2011 in west central Minnesota to evaluate yields, seed quality, economics, and within-field energy balance of winter camelina–soybean double- and relay-cropping systems compared with a conventional monocropped full-season soybean. Systems included methods to hasten camelina harvest (e.g., swathing and desiccating) to promote early soybean growth. Camelina seed yields were unaffected by cropping system and ranged from 1.1 to 1.3 Mg ha–¹. Relay-cropped soybean yields were greater than double-cropped soybean and were 58 to 83% of that for the monocropped control. Seed oil and protein content of double- and relay-cropped soybean were comparable to their monocropped counterpart and combined seed oil yield for the dual crop systems was as much as 50% greater. Net economic returns for the relay-crop treatments were competitive with that of the full-season soybean. Moreover, net energy of the relay-crop treatments was generally as high as the sole soybean crop, but energy efficiency (outputs/inputs) was less due to greater inputs. Results indicate that dual cropping of winter camelina with soybean is agronomically viable for the upper Midwest and might be an attractive system to growers seeking a “cash” cover crop.

Agricultural management practices that enhance C sequestration, reduce greenhouse gas emission (nitrous oxide [N₂O], methane [CH₄], and carbon dioxide [CO₂]), and promote productivity are needed to mitigate global warming without sacrificing food production. The objectives of the study were to compare productivity, greenhouse gas emission, and change in soil C over time and to assess whether global warming potential and global warming potential per unit biomass produced were reduced through combined mitigation strategies when implemented in the northern U.S. Corn Belt. The systems compared were (i) business as usual (BAU); (ii) maximum C sequestration (MAXC); and (iii) optimum greenhouse gas benefit (OGGB). Biomass production, greenhouse gas flux change in total and organic soil C, and global warming potential were compared among the three systems. Soil organic C accumulated only in the surface 0 to 5 cm. Three-year average emission of N₂O and CH was similar among all management systems. When integrated from planting to planting, N₂O emission was similar for MAXC and OGGB systems, although only MAXC was fertilized. Overall, the three systems had similar global warming potential based on 4-yr changes in soil organic C, but average rotation biomass was less in the OGGB systems. Global warming potential per dry crop yield was the least for the MAXC system and the most for OGGB system. This suggests management practices designed to reduce global warming potential can be achieved without a loss of productivity. For example, MAXC systems over time may provide sufficient soil C sequestration to offset associated greenhouse gas emission.

Recent soil and crop management technologies have potential for mitigating greenhouse gas emissions; however, these management strategies must be profitable if they are to be adopted by producers. The economic feasibility of reducing net greenhouse gas emissions in irrigated cropping systems was evaluated for 5 yr on a Fort Collins clay loam soil (a fine-loamy, mixed, superactive, mesic Aridic Haplustalf). Cropping systems included conventional tillage continuous corn (Zea mays L.) (CT-CC), no-till continuous corn (NT-CC), and no-till corn-bean (NT-CB) including 1 yr soybean [Glycine max (L.) Merr.] and 1 yr dry bean (Phaseolus vulgaris L.). The study included six N fertilization rates ranging from 0 to 246 kg ha -1 . Results showed highest average net returns for NT-CB, exceeding net returns for NT-CC and CT-CC by US$182 and US$228 ha -1 , respectively, at economically optimum N fertilizer rates. Net global warming potential (GWP) generally increased with increasing N fertilizer rate with the exception of NT-CC, where net GWP initially declined and then increased at higher N rates. Combining economic and net GWP measurements showed that producers have an economic incentive to switch from CT-CC to NT-CB, increasing annual average net returns by US$228 ha -1 while reducing annual net GWP by 929 kg CO 2 equivalents ha -1 . The greatest GWP reductions (1463 kg CO 2 equivalents ha -1 ) could be achieved by switching from CT-CC to NT-CC while also increasing net returns, but the presence of a more profitable NT-CB alternative means NT-CC is unlikely to be chosen without additional economic incentives.

The agricultural sector is a small but significant contributor to the overall anthropogenic greenhouse gas (GHG) emission and a major contributor of N 2 O emission in the United States. Land management practices or systems that reduce GHG emission would aid in slowing climate change. We measured the emission of CO 2 , CH 4 , and N 2 O from three management scenarios: business as usual (BAU), maximum C sequestration (MAXC), and optimum greenhouse gas benefits (OGGB). The BAU scenario was chisel or moldboard plowed, fertilized, in a 2-yr rotation (corn [Zea mays L.]-soybean [Glycine max (L.) Merr.]). The MAXC and OGGB scenarios were strip tilled in a 4-yr rotation (corn-soybean-wheat [Triticum aestivum L.]/alfalfa [Medicago sativa L.]-alfalfa). The MAXC received fertilizer inputs but the OGGB scenario was not fertilized. Nitrous oxide, CO 2 , and CH 4 emissions were collected using vented static chambers. Carbon dioxide flux increased briefly following tillage, but the impact of tillage was negligible when CO 2 flux was integrated across an entire year. The soil tended to be neutral to a slight CH 4 sink under these managements scenarios. The N 2 O flux during spring thaw accounted for up to 65% of its annual emission, compared with 6% or less due to application ofN fertilizer. Annual cumulative emissions of CO 2 , CH 4 , and N 2 O did not vary significantly among these three management scenarios. Reducing tillage and increasing the length of the crop rotation did not appreciably change GHG emissions. Strategies that reduce N 2 O flux during spring thaw could reduce annual N 2 O emission.

While no-till (NT) cropping systems can provide conservation benefits in the northern Corn Belt, adoption has been low due to concerns about potential yield reductions and economic risk. Strip-tillage (ST) systems have been proposed as an alternative that may provide many of the conservation benefits of NT while maintaining productivity and economic returns. The objectives of this study were to evaluate the effects of NT and five ST alternatives: fall residue management (Fall RM), Fall RM + ST, spring residue management (Spring RM), Spring RM + ST, and Fall RM + Subsoil, relative to conventional moldboard plow (MP) and chisel plow (CP) tillage systems on corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields and economic risks and returns. Average yields over the 7-yr study were not significantly different among tillage systems, but average net returns for NT, Fall RM, and Spring RM were $85, 92, and 53 ha -1 higher, respectively, than for MP. Risk analysis showed tillage system preferences ranked as: Fall RM > NT > Fall RM + ST > Spring RM + ST, Spring RM > CP > Fall RM + Subsoil > MP for risk neutral or risk averse producers facing uncertain yield, crop price, and input price conditions. Thus, ST and NT may be economically viable alternatives to conventional tillage systems for corn and soybean production in the northern Corn Belt.

Summary To further understand the impact of tillage on carbon dioxide (CO2) emission, we compare the performance of two conceptual models that describe CO2 emission after tillage as a function of the non-tilled emission plus a correction resulting from the tillage disturbance. The models assume that C in the readily decomposable organic matter follows a first-order reaction kinetics equation as dCsoilðtÞ dt ¼� kCsoilðtÞ and that soil C-CO2 emission is proportional to the C decay rate in soil, where Csoil(t) is the available labile soil C (g m � 2 ) at any time (t) and k is the decay constant (time � 1 ). Two possible relationships are derived between non-tilled (FNT) and tilled (FT) soil fluxes

Conversion of irrigated cropland from conventional tillage (CT) to no-till (NT) could have several environmental benefi ts including reduced erosion potential, reduction of greenhouse gas emissions, and conservation of water. However NT must be economically viable if it is to be adopted. Costs of production and economic returns were evaluated for an irrigated, continuous corn (Zea mays L.) system under CT and NT over 6 yr on a clay loam soil in northern Colorado. Yield responses to N fertilization were included to determine economic optimum fertilization rates under each tillage system. Corn grain yields at economic optimum N fertilizer rates were 1.1 to 1.4 Mg ha –1 lower for NT than for CT. However, net returns were $46 to 74 ha –1 higher for NT than for CT due to reductions in operating costs of $57 to 114 ha –1 and reductions in machinery ownership costs of $87 to 90 ha –1 . Operating cost savings were realized largely due to fuel and labor reductions of 75% and 71 to 72%, respectively, and in spite of higher N fertilizer requirements of 16 to 55 kg ha –1 for NT compared to CT. No-till, irrigated, continuous corn appears to be an economically viable option for replacing CT production systems in the central Great Plains, especially when combined with the environmental benefi ts of the NT system.

Many environmental benefits accrue from reducing tillage and increasing crop diversity; however, economic factors often encourage the continued use of intensive tillage and specialized crop production. This study examined crop yields, input costs, and economic returns during the transition to a range of cropping system alternatives in the northern Corn Belt region, including different system (organic, conventional), tillage (conventional, strip-tillage), rotation (corn-soybean, corn-soybean-wheat/alfalfa-alfalfa) [Zea mays L., Glycine max (L.) Merr., Triticum aestivum L., Medicago sativa L.], and fertility (no fertilizer/manure, fertilizer/manure applied at recommended rates) treatments. Increasing crop diversity and reducing tillage intensity reduced total costs by$24-102 ha -1 within conventional treatments, and $16-107 ha -1 within organic treatments. Yields of corn, soybean, and wheat were more than 15% lower when using organic vs. the highest yielding conventional practices. Treatments receiving fertilizer or manure had wheat yields more than 0.3 Mg ha -1 and alfalfa yields 2.7 Mg ha -1 higher than treatments that did not receive fertilizer or manure. Within conventional systems, no significant differences in the 4-yr net present value of net returns were detected for tillage and rotation alternatives. Net present values for the organic systems without organic price premiums were at least $692 ha -1 lower than for the best conventional systems suggesting a barrier to the adoption of these systems should organic price premiums decline. However, when organic price premiums were included, most organic treatments had net present values comparable to or exceeding those from conventional treatments.

Cuphea (Cuphea viscosissima Jacq. 3 C. lanceolata W.T. Aiton) is a potential new oilseed crop for temperate regions. Harvesting problems occur because current varieties are nondeterminate and shatter seeds. Because swathing may help overcome some of these problems, cuphea was swathed and allowed to dry in windrows for 0, 1, 2, 3, and 4 wk before combining. Measured variables at the time of combining were windrow weight, seed water content, seed yield, seed oil content, and post-swathing evaporation (Eps). Windrow weights decreased from about 40 to 14 Mg ha 21 as combining was delayed until 3 wk after swathing. Weights decreased over time due to dehydration and leaf abscission, and they were associated hyperbolically with Eps. Similarly, seed water content decreased from about 670 g kg 21 at swathing to about 250 g kg 21 at 30 mm Eps. Seed shattering apparently was low as high yields were maintained each year until after at least 30 mm Eps. Seed oil content was affected only slightly by delayed combining dates. Thus, swathing and windrowing cuphea and delaying combining until 30 mm Eps substantially decreased the weight of material processed by the combine, reduced seed water content, but maintained high seed yields and seed oil contents. F OR many recently domesticated seed crops, nondeterminate growth habit and propensity for seed shattering reduce harvesting efficiency and harvestable seed yields. At time of harvest, nondeterminate crops may support green leaves and stems, and their seeds can be at a wide range of maturities and moisture levels, all of which decrease efficient processing in modern harvesting equipment. Long-term solutions to these problems involve breeding varieties whose growth habits are determinate, mature plants dry rapidly, and ripened fruits retain seeds. With these traits crops can be left in the field to mature and dry naturally. Unfortunately,breedingnewvarietiesiscostlyandtime consuming and, therefore, near-term solutions also are needed during the domestication of new crops. One nearterm solution involves application of desiccants. When followed by direct combining, desiccants can reduce high plantmoisturecontentatharvestandarresttheshattering process in ripening fruits. Another near-term solution involves swathing and windrowing followed by drying of windrows and then combining. Such harvesting alternatives are common for many partially or recently domesticated crops (e.g., Simpson, 1993; Thomas et al., 1991). Cuphea (Cuphea viscosissima Jacq. 3 C. lanceolata W.T. Aiton) is a newly domesticated crop suffering from the aforementioned harvesting problems. Cuphea is of

May for the northern part of the state. In terms of grain yield, the optimum time for planting corn in southern Cold, wet soils, coupled with a short growing season, create a Minnesota is considered to be late April to early May narrow window of optimum time for planting corn (Zea mays L.) in the northern Corn Belt. Temperature-activated polymer (TAP) (Hicks et al., 1977). Although in some years soil tempercoatings designed to inhibit planted seed from imbibing water until atures are warm enough to plant corn as early as 20 adequate soil temperatures are reached to promote germination and April in southern Minnesota and 25 April in northern emergence may offer potential for planting corn exceptionally early. parts of the state, generally about 50% of the land area A study from 2000 to 2002 was conducted in west central Minnesota devoted to corn production is sown by May 11 (Hardon a Barnes soil (Calcic Hapludoll) to determine the potential for man and Gunsolus, 2002). Delaying corn planting beearlier-than-average planting of TAP-coated corn seed. The objective yond an optimum period can result in substantial yield was to compare emergence characteristics of coated and uncoated loss. It has been suggested that in Minnesota, for each hybrid corn planted early and at a near-average planting date. Seed day corn seeding is delayed between 1 May and the end planted 29 Mar. 2000 and 24 Apr. 2002 remained in the soil for as of the month, there is approximately 0.5% d 1 yield loss long as 26 to 32 d before emerging. In these instances, stands from TAP-coated seed, which ranged from 60 to 90% of seed planted, (Hardman and Gunsolus, 2002). were generally greater than those of uncoated seed, which ranged One of the greatest barriers preventing early corn from 49 to 68%. Stand establishment and time required to obtain planting in the northern Corn Belt is cold, wet soils. 50% and from 10 to 90% emergence for most early planted coating This can be problematic where heavy soils predominate hybrid seed combinations were similar to uncoated seed planted at and conservation tillage practices are used (Gupta et near-average planting dates of 1, 14, and 16 May in 2000, 2001, and al., 1988; TeKrony et al., 1989). Temperature is the 2002, respectively. When both coated and uncoated seed were sown primary factor affecting corn germination and seedling at an average planting date, stand establishment was similar, but emergence, although soil moisture is also an important emergencefor coatedseed wasgenerallydelayed. Resultsof thisstudy factor (Schneider and Gupta, 1985). During spring indicate that TAP coatings protected seeds from injury caused by planting in the northern fringes of the Corn Belt, soils extended exposure to cold soils, and therefore, might be a useful management tool for early corn planting. are often at or near field capacity for moisture (Dwyer et al., 2000). Therefore, lack of soil moisture is typically not a primary deterrent of emergence. Planting corn too early can result in seeds imbibing water but not

Resin extraction of soil permits evaluation of ratios of readily extracted elements and correlation of concentrations obtained with crop yield. This information provides guidance on potential genotype selection and fertility management. Two hybrids of maize (Zea mays L.), designated 2292 and 3895, were grown annually in rotational succession on a 3.2-ha site with soybean (Glycine max L.) and wheat (Triticum aestivum L.). Soil samples (0–15 cm) were extracted with ion-exchange resins and extracts were analysed with inductively coupled plasma. Data were regressed against crop yield using stepwise multiple correlation methods. Each hybrid was sensitive to unique combinations of extracted chemistries. Both hybrids of maize were sensitive to the resin-extractable V : (V + P) molar ratio and potential losses of ‡ 20 % were indicated as the ratio approached 0.2. A positive response to the Mg : (Mg + Ca) resin-extractable ratio was noted for maize hybrid 2292 in each of three successive years. Changes of yield potentials associated with the Mg : (Mg + Ca) ratio for hybrid 2292 ranged from none to ‡ 20 % as the ratio ranged from 0.2 to about 0.8. The results indicate that, in the presence of large extractable concentrations of competing or inhibitory ions, different approaches to nutrient management in the form of fertilizer nutrient analysis, application, and genotype selection are needed to overcome effects of competing ions.

Contemporary agricultural land use is dominated by an emphasis on provisioning services by applying energy-intensive inputs through relatively uniform production systems across variable landscapes. This approach to agricultural land use is not sustainable. Achieving sustainable use of agricultural land should instead focus on the application of innovative management systems that provide multiple ecosystem services on lands with varying inherent qualities. Integrated agricultural systems (IAS) represent an alternative approach to prevailing land use, whereby site-adapted enterprises are implemented to enhance synergistic resource transfer among enterprises and sustainable delivery of ecosystem services. Sustainable deployment of IAS on agricultural land involves placing the “right enterprise” at the “right intensity” at the “right time” on the “right location,” with the inherent attributes of location providing guidance for management decisions. There is an urgent need to design IAS that enhance delivery of ecosystem services while ensuring land potential thresholds are not exceeded.

Weed control decisions are modeled in an endogenous risk framework where a producer invests in self-insurance and self-protection to reduce the severity of a realized pest infestation, or reduce the likelihood the infestation occurs. Self-insurance and self-protection are risk-reducing technologies that capture both the type and quantity of herbicides used. We supply conditions to unambiguously sign the effects of an increase in the probability of application or effectiveness failure and increased application or effectiveness uncertainty on optimal herbicide choices. If self-protection and self-insurance are stochastic substitutes, non-point source pollution policies targeted to reduce herbicide loadings can increase the use of more persistent herbicides. Policies that decrease loadings by reducing total mass may induce a substitution to herbicides more damaging or more likely to be transported to sensitive areas.

Nonpoint pollution from agricultural production continues to force regulators to rethink policies aimed at reducing input sources such as herbicides and fertilisers. This paper considers how a producer's choice of an input strategy defined by application rate or persistence affects input-use patterns, and consequently, nonpoint pollution. Working within an endogenous risk framework, we explore how input sets with herbicides defined either as self-insurance or self-protection are affected by increased risk of herbicide treatment failure. Our results suggest that increased risk will generally decrease both herbicide and fertiliser application rates, resulting in the use of less flexible and less persistent herbicides. In addition, a quantity constraint policy restricting the amount of herbicide applied will decrease the amount of fertiliser applied.