iRelying more on biological N~ fixation has been suggested as a way to meet one of the major challenges of agricultural sustainability. A study was conducted to compare the fate of applied legume and fertilizer N in a long-term cropping systems experiment. Nitrogen-15-1abeled red clover (Trifolium pratense L.) and (NH4)2SO4 were applied microplots within the low-input and conventional cropping systems of the Farming Systems Trial at the Rodale Institute Research Center in Pennsylvania. The ~SN was applied to soil and traced into corn (Zea mays L.) in 1987 and 1988. Residual ~SN was also traced into second-year spring barley (Hordeum vulgare L.). Legume and fertilizer ~SN remaining in soil was measured and loss of N was calculated by difference. More fertilizer than legume N was recovered by crops (40 vs. 17% of input), more legume than fertilizer N was retained in soil (47 vs. 17% of input), and similar amounts of N from both sources were lost from the cropping systems (39% of input) over the 2-yr period. More fertilizer than legume N was lost during the year of application (38 vs. 18% of input), but more legume than fertilizer N was lost the year after application (17 vs. 4% of input). Residual fertilizer and legume ~SN was distributed similarly among soil fractions. Soil microbial biomass was larger in the legume-based system. A larger, but not necessarily more active, soil microbial biomass was probably responsible for the greater soil N supplying capacity in the legume-based compared with fertilizerbased system. M ANAGING NITROGEN INPUTS in crop production systems to achieve economic and environmental sustainability is a major challenge facing agriculture. Relying: less on commercial fertilizer N and more on biological N2 fixation by legumes has been suggested as a way to meet this challenge (Keeney, 1982; National Academy of Sciences, 1989). Nitrogen-15 methodology is recognized as a valuable tool for determining the fate and behavior of N applied in the environment (Hauck, 1971(Hauck, , 1982 L'Annunziata and Legg, 1984). Field experiments using SN have studied the recovery of fertilizer N by crops and have documented that use efficiency varies due to a number of factors, including timing and method of N application, tillage method, and climate. A well-managed, firstyear, single-harvested crop recovers between 50 and 70% of applied fertilizer N (Allison, 1966; Stanford, 1973). In addition, 10 to 40% of applied fertilizer N may remain in soil, 5 to 10% may be lost by leaching, and 10 to 30% may be lost to the atmosphere in gaseous forms (Kundler, 1970; Westerman et al., 1972).Studies evaluating the fate of ~SN from legume residues decomposing under field conditions concluded that: (i) <30% of legume N was recovered by a subsequent nonlegume crop; (ii) large amounts of legume N were retained in soil, mostly in organic forms; (iii) total recovery of le- 910gume N in crops and soils after 1 yr averaged 70 to 90%; and (iv) <5% of legume N from the original application was recovered by a second nonle...

sufficiently to survive the winter. Cover crop residue can modify the conditions under which weeds germinate Cover crops often reduce density and biomass of annual weeds in or regrow in the spring. Such effects could be due to no-till cropping systems. However, cover crops that over-winter also changes in soil temperature, increase in soil moisture, have the potential to reduce crop yield. Currently, there is an interest in annual medics (Medicago spp.) and other annual legumes that release of allelopathic chemicals, and physical impediwinter-kill for use as cover crops in midwestern grain cropping systems. ments to weed seedlings (Facelli and Pickett, 1991; Teas-A 2-yr study was conducted at East Lansing and the Kellogg Biological dale, 1996; Teasdale and Mohler, 1993). Station, Michigan, to investigate the influence of annual legume cover Many legume species that are used as cover crops in crops on weed populations. Two annual medic species [burr medic (M. no-till corn production are winter annuals or short-lived polymorpha cv. Santiago) and barrel medic (M. truncatula Gaertn. cv. perennials. In northern regions of the USA, over-win-Mogul)], berseem clover (Trifolium alexandrinum L. cv. Bigbee), tering species are normally established in the summer and medium red clover (Trifolium pratense L.) were no-till seeded or fall and accumulate most of their biomass when they as cover crops into winter wheat (Triticum aestivum L.) stubble in

Frost‐seeding a legume into an established stand of winter wheat (Triticum aestivum L.) or interseeding a legume into a small grain at planting has potential to provide the benefits of a legume green manure while still allowing for the harvest of a revenue‐producing crop. Field studies were conducted at three Michigan locations to quantify N accumulation by alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) frost‐seeded into winter wheat or interseeded with oat (A vena sativa L.) and to evaluate the response of a subsequent corn (Zea mays L.) crop to legume and fertilizer N. Cropping sequences included corn following either wheat, wheat frost‐seeded with a legume, oat, or oat interseeded with a legume. Corn was planted either no‐till following wheat or conventionally (moldboard plow) following oat. Frost‐seeding and interseeding alfalfa and red clover had no effect on small grain yield, and stands of alfalfa and red clover were adequate (>13 plants/sq ft) even though N fertilizer had been applied to the small grains. Nitrogen accumulation did not differ among alfalfa or red clover cultivars, and averaged 80, 50, and 116 lb N/acre for alfalfa; and 96, 99, and 176 lb N/acre for red clover frost‐seeded into winter wheat at the three locations. When interseeded with oat, alfalfa contained an average of 44 lb N/acre and red clover contained an average of 33 lb N/acre prior to fall plowing. Corn response to the frost‐seeded legumes differed among locations due primarily to differences in precipitation during the weeks just prior to and following corn planting. When soil water was adequate, corn grain yields following the small grain seeded with a legume were 4 to 62% greater than following the small grain without the legume. With below‐normal precipitation following corn planting, corn grain yields in the legume systems were reduced by 3 to 27%, primarily due to delayed and reduced emergence. Fertilizer replacement values based on grain yield ranged from 0 to 49 lb N/acre for alfalfa and from 0 to 113 lb N/acre for red clover. Response of corn to the preceding legume differed by year, location, and seeding method.

With the current interest in sustainable agricultural systems, the use of legumes in crop rotations to provide N to subsequent crops is increasing. The objective of this study was to quantify the N contribution from different alfalfa (Medicago sativa L.) plant parts to a subsequent corn (Zea mays L.) crop, various soil fractions, and a 2nd yr spring barley (Hordeum vulgare L.) crop. The study was conducted at two field locations in Michigan, on a Capac loam (fineloamy, mixed, mesic, Aerie Ochraqualf) in East Lansing (EL) and on an Oshtemo sandy loam (coarse‐loamy, mixed, mesic, Typic Hapludalf) at the Kellogg Biological Station (KBS) in Hickory Corners. Alfalfa shoots and roots/crowns labeled with 15N were applied separately to microplots in Fall 1985 and Spring 1986 at a rate equivalent to 112 kg N ha−1. Corn was harvested and soil was sampled from all microplots in Fall 1986 and analyzed for 15N. Corn recovered 17 and 25% of the alfalfa‐15N applied to the loam and sandy loam soils at ELand KBS, respectively. Alfalfa‐15N remaining in soil averaged 46% of the initial input for both locations. Most (96%) of the alfalfa‐15N remaining in soil was recovered in the organic fraction, with microbial biomass accounting for 18% of this recovery. More 15N was recovered by corn and in soil from alfalfa shoots than roots/crowns at both locations, and from spring‐incorporated than fall‐incorporated plant material on the loam soil. Only 1% of the alfalfa‐15N from the original application was recovered by a 2nd yr spring barley crop at both locations

Introduction Diet-related disease is disproportionally concentrated in low-income communities where fruit and vegetable consumption is far below guidelines. To address financial barriers, Double Up Food Bucks (DUFB)—a statewide healthy food incentive—matches Supplemental Nutrition Assistance Program (SNAP) funds spent at farmers markets. However, incentive use is limited. This study examined the impact of a brief waiting room–based intervention about DUFB on program utilization and produce consumption. Study design Longitudinal, repeated measures, quasi-experimental trial. Setting/participants SNAP—enrolled adults at a health center in a low-income, racially and ethnically diverse area of Southeast Michigan. Intervention Participants received a brief explanation of DUFB, written program materials, a map highlighting market locations and hours, and an initial $10 market voucher. DUFB use and produce consumption were measured through four surveys over 5 months (August 2014–January 2015). Main outcome measures Outcome measures included DUFB use and fruit and vegetable consumption (analyses conducted in 2015–2016). Results A total of 302 eligible adults were identified, and 177 (59%) enrolled. One hundred twenty-seven (72%) completed all surveys. At baseline, 57% of participants reported shopping at a farmers market within the last year; 18% had previously used DUFB. By the end of the DUFB season, participants were significantly more likely to report DUFB use than at baseline (AOR=19.2, 95% CI=10.3, 35.5, p<0.001), with 69% of participants reporting use of DUFB at least once, and 34% reporting use of DUFB three or more times. Adjusted fruit and vegetable consumption increased from baseline by 0.65 servings/day (95% CI=0.37, 0.93, p<0.001) at 3 months, and remained 0.62 servings/day (95% CI=0.32, 0.92, p<0.001) higher than baseline 2 months post-DUFB season. Conclusions A brief clinic-based intervention was associated with a nearly fourfold increase in uptake of a SNAP incentive, as well as clinically significant increases in produce consumption. Results suggested sustained behavior change even once the financial incentive was no longer available. Providing information about healthy food incentives is a low-cost, easily implemented intervention that may increase produce consumption among low-income patients.