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.

Open surface inlets that connect to subsurface tile drainage systems provide a direct pathway for movement of sediment, nutrients, and agrochemicals to surface waters. This study was conducted to determine the reduction in drainage effluent total suspended sediment (TSS) and phosphorus (P) concentrations and loads when open surface inlets were replaced with blind (in gravel capped with 30 cm of soil) or gravel (in very coarse sand/fine gravel) inlets. In Indiana, a pair of closed depressions in adjacent fields was fitted with open inlet tile risers and blind inlets in 2005 and monitored for flow and water chemistry. Paired comparisons on a storm event basis during the growing season for years 2006 to 2013 showed that TSS loads were 40.4 and 14.4 kg ha event for tile risers and blind inlets, respectively. Total P (TP) and soluble reactive P (SRP) loads were 66 and 50% less for the blind inlets, respectively. In Minnesota, TSS and SRP concentrations were monitored for 3 yr before and after modification of 24 open inlets to gravel inlets in an unreplicated large-field on-farm study. Median TSS concentrations were 97 and 8.3 mg L and median SRP concentrations were 0.099 and 0.064 mg L for the open inlet and gravel inlet periods, respectively. Median TSS and SRP concentrations were elevated for snowmelt vs. non-snowmelt seasons for open and gravel inlets. Both replacement designs reduced suspended sediment and P concentrations and loads. The Indiana study suggests blind inlets will be effective beyond a 10-yr service life.

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.

Soils under continuous corn (Zea mays L.) silage production are often subjected to heavy traffic and tillage, which can degrade soil structure and physical properties. Cover crops have been shown to benefit soil structure, but the effects of double‐cropping on soil structure and physical properties are unknown. Our objective was to compare the soil structure and physical properties under rye (Secale cereale L.) and corn silage double‐cropping with those under continuous corn silage in Minnesota during the 2007–2008 cropping year. A conventional tillage corn silage system served as the control. Double‐crop treatments were conventional tillage winter rye harvested in May or June followed by no‐till corn silage. Relative to the control, the double‐cropping systems exhibited superior soil structure with up to 57% better visual soil structure scores and up to 16% smaller mean weight aggregate diameter. Visual soil structure scores exhibited seasonal dynamics with significant treatment effects in November and June but not in May when the structural assessment was conducted shortly after preplant tillage in the control. The double‐cropping system increased the resilience of the soil to traffic. The saturated hydraulic conductivity in wheel‐tracked interrows was 375% higher in the double‐cropping system relative to the control in July. Both the rye and the absence of tillage before corn planting may have contributed to this improved resilience. Heavy traffic and tillage in continuous corn silage production systems can degrade soil structure and physical properties; however, the rye–corn silage double‐cropping system provided a measure of protection.

Core Ideas Fraction of available water capacity (FAW) was determined from measured soil moisture. Wildfire relationships were compared for FAW and Keetch–Byram drought index (KBDI). Growing‐season wildfire danger was more accurately represented by FAW than KBDI. Neither FAW nor KBDI alone accurately represented dormant‐season wildfire danger. We recommend replacing KBDI with FAW in growing‐season wildfire danger assessments In situ soil moisture measurements have the potential to improve wildfire danger assessments, which often rely on the Keetch–Byram Drought Index (KBDI) as a soil moisture surrogate. However, the relative merits of measured soil moisture and KBDI as indicators of wildfire danger are unknown. Therefore, our objectives were to (i) identify relationships between drought indices (KBDI or fraction of available water capacity, FAW) and wildfire size for 34,939 growing and dormant‐season wildfires, (ii) compare relationships between each drought index and wildfire probability for 501 large (≥ 405 ha) growing‐season and dormant‐season wildfires, and (iii) quantify relationships between KBDI and FAW for each season in Oklahoma, the United States. Neither KBDI nor FAW accurately represented dormant‐season wildfire danger, with wildfires ≥ 121 ha occurring across nearly the entire range of each index. During the growing season, however, we found that a smaller percentage of wildfires ≥ 121 ha occurred under extreme levels of KBDI than under equivalent levels of FAW (66% vs. 81%), and a logistic regression model based on FAW correctly classified more growing‐season days with large wildfires than the KBDI model (84% vs. 79%). Furthermore, while FAW represented soil moisture in near real‐time, KBDI responded slower to soil drying and recharge, so FAW provided about 10 d earlier warning of extreme wildfire potential for the 10 largest growing‐season wildfires in our study. We therefore recommend replacing KBDI with FAW in growing‐season wildfire danger assessments in Oklahoma and regions with similar climate (temperate, subhumid to semiarid) and vegetation types (primarily herbaceous).