A winter rye (Secale cereale L.) cover crop can be seeded after corn (Zea mays L.) silage to mitigate some of the environmental concerns associated with corn silage production. Rye can be managed as a cover crop by chemical termination or harvested for forage. A field study was conducted in Morris, MN in 2008 and 2009 to determine the impact of killed vs. harvested rye cover crops on soil moisture and NO3–N, and to monitor the impact of the rye on subsequent corn yield. Corn for silage was seeded either after winter fallow (control), after a rye cover crop terminated 3 to 4 wk before corn planting (killed rye), or after a rye forage crop harvested no more than 2 d before corn planting (harvested rye). Soil moisture after killed rye was similar to the control, but after harvested rye was 16% lower. Available soil NO3–N was decreased after both killed rye (35%) and harvested rye (59%) compared to the control. Corn biomass yield after killed rye was similar to the control, but yield following harvested rye was reduced by 4.5 Mg ha−1 Total forage biomass yield (silage + rye) was similar for all treatments. This work demonstrates that the environmental benefits of a winter rye cover crop can be achieved without impacting corn yield, but the later termination required for rye forage production resulted in soil resource depletion and negatively impacted corn silage yield.

The increasing availability of soil moisture data presents an opportunity for its use in wildfire danger assessments, but research regarding the influence of soil moisture on wildfires is scarce. Our objective was to identify relationships between soil moisture and wildfire size for Oklahoma wildfires during the growing (May-October) and dormant seasons (November-April). we hypothesized that soil moisture influences wildfire size when vegetation is growing but is less important when most vegetation is dead or dormant. soil moisture, as fraction of available water capacity (FAw), and commonly measured weather variables were determined for 38,419 wildfires from 2000-2012. wildfires were grouped by size class (<4.05, ³4.05 and <40.5, ³40.5 and <121, ³121 and <405, and ³405 ha), and the Kruskal-wallis test with multiple comparisons was used to identify differences in each variable between wildfire size classes and seasons. Large fires occurred at lower FAw than small fires during both seasons (P < 0.001), but growing-season wildfires ³405 ha occurred over a narrow range of FAw (0.05-0.46) whereas dormant-season fires of this size occurred across the entire range of FAw (0.05-1.05). For growing-season fires ³ 121 ha, 91% occurred at FAw < 0.5 and 77% occurred at FAw < 0.2. Our finding that large growing-season wildfires occurred exclusively under conditions of low soil moisture highlights the need to develop methods to use soil moisture data in wildfire danger assessments.Abbreviations: AWC, available water capacity; FAW, fraction of available water capacity; KBDI, Keetch-Byram Drought Index; LFM, live fuel moisture; PAW, plant available water.

Measured soil moisture data may improve wildfire probability assessments because soil moisture is physically linked to fuel production and live fuel moisture, yet models characterising soil moisture–wildfire relationships have not been developed. We therefore described the relationships between measured soil moisture (concurrent and antecedent), as fraction of available water capacity (FAW), and large (≥405 ha) wildfire occurrence during the growing (May–October) and dormant (November–April) seasons from 2000 to 2012 in Oklahoma, USA. Wildfires were predominantly grass and brush fires but occurred across multiple fuel types including forests. Below-average FAW coincided with high wildfire occurrence each season. Wildfire probability during the growing season was 0.18 when concurrent FAW was 0.5 (a threshold for plant water stress) but was 0.60 when concurrent FAW was 0.2 (extreme drought). Dormant season wildfire probability was influenced not only by concurrent but also by antecedent FAW. Dormant season wildfire probability was 0.29 and 0.09 when FAW during the previous growing season was 0.9 (near ideal for plant growth) and 0.2, respectively. Therefore, although a wet growing season coincided with reduced wildfire probability that season, it also coincided with increased wildfire probability the following dormant season, suggesting that the mechanisms by which soil moisture influences wildfire probability are seasonally dependent.

Recent proliferation of large dairies has prompted concern regarding environmental impacts of associated corn silage production and high-rate manure application. Our objectives were to compare environmental impacts and forage production of monocrop corn (Zea mays L.) silage and rye (Secale cereal L.)-corn silage double-crop systems with multiple corn planting dates and highrate manure application near Morris, MN. From 2007 to 2009, corn for silage was seeded into a silt loam as a monocrop in early and mid-May and as a double-crop aft er rye in mid-May and early June. Manure was fall applied annually at average total N and P rates of 393 and 109 kg ha −1 , respectively. Double-cropping reduced total forage dry matter (DM) yield 2 of 3 yr and reduced corn DM yield 15 to 25%. Soil NO 3 -N to 90 cm accumulated at an average rate of 71 kg N ha −1 yr −1 with monocropping, but accumulation was not observed with double-cropping. Soil organic C concentration from 0 to 5 cm increased in the monocrop (18%) and double-crop (26%) systems over 3 yr. Average soil solution NO 3 -N concentration was high with monocropping (52 mg L −1 ) and double-cropping (37 mg L −1 ), but estimated leaching load averaged only 8 kg ha −1 yr −1 . Fall and spring ground cover was oft en less than 10% with monocropping but was usually greater than 30% with double-cropping. Th e primary environmental concerns identifi ed for monocrop corn silage were soil NO 3 -N buildup and inadequate ground cover. Doublecropping addressed each concern but oft en decreased forage production.

Winter rye (Secale cereale L.) is a common cover crop in the Upper Midwest United States with potential as a forage crop; but little is known about the effect of maturity on its spring forage yield and quality. Our objective was to determine the forage yield and quality of three winter rye cultivars at six different maturities in four environments. The yield response to increased maturity was quadratic and variable over environment with ranges at boot (Zadok 41) of 1.2 to 2.7 tons/acre, at heading (Zadok 51) 1.4 to 4.2 tons/acre, and at dough (Zadok 81) of 4.4 to 9.5 tons/acre. Forage crude protein (CP), neutral detergent fiber digestibility (NDFD), and digestible dry matter (DDM) decreased with maturity while neutral detergent fiber (NDF) increased. Average NDF digestibility decreased linearly from 82.5% at tillering to 44.1% at soft dough. Rye cultivars had similar forage yield and quality except for CP. Vitallo had lower CP levels than Rymin or Spooner. Producers can maximize yield by harvesting at dough (Zadok 81) or forage quality by harvesting at tillering (Zadok 21). Rye provides good yield and high quality forage at many environments and maturities.