Effect of Long-Term Integrated Crop and Livestock Systems on Forage Finishing, Soil Fertility, Nitrogen Mineralization, Carbon Sequestration, and Profitability

During the first year of this project, extreme drought hampered growing-season soil fertility analysis and most other physical property measurements. Although a limited amount of soil data was collected and analyzed. Soil physical property measurements are during the 7th year of the multi-crop rotation that includes yearling steer grazing of the forage crops in the rotation. Measurements for soil water infiltration, wind erodible fraction, air-dry and field-moist aggregate stability were measured. In addition, seasonal N mineralization from the 2016 growing season were completed and an index of NH4-N mineralization potential (ppm) depict in the attached chart Index-of-mineralization-potential_Cihacek. During 2018 N mineralization in the semi-arid region of western North Dakota was again evaluated and from results it is estimated that 16.8 pounds of N is mineralized for each 1% increase in soil organic matter.  

Soil Water Infiltration: Infiltration rate was measured after soil saturation. Infiltration rate between spring wheat (SW) grown continuously (Control) and spring wheat grown in the multi-crop rotation did not differ. However, rotation SW hand an average infiltration rate of 1.07 in/hr. compared to 0.75 in/ hr. for the continuous SW (27 mm/hr. vs. 19 mm/hr.). This was likely due to better aggregation (probably fine aggregation) for the rotation SW than the continuous SW. Under the dry conditions of the 2017 crop year, the rotation SW tended to have better structure due to the crop diversity.

Wind Erodible Fraction: Numerical differences were measured, but the differences were not significant. However, the rotation SW had a 40.5% wind erodible fraction compared to the continuous SW which had a 28.3% erodible fraction. Again, this is likely due to the dry conditions where the crop rotation had a massive structure compared to the rotation SW which had a lot of strong fine aggregates (<0.84 mm). Rotation promoted better aggregation due to the crop diversity.

Air-Dry and field-moist Aggregate Stability: No significant difference measured. The rotation SW had a slightly higher level of water stable aggregates (92.6%) compared to the continuous wheat (91.2%). Again, crop diversity in the rotation slightly promoted stronger aggregates and these observations are interrelated to the previously described observations.

2016 Soil N Mineralization: There is no N mineralization for the 2017 growing season due to the extremely dry conditions. A linear regression on soil OM vs. N mineralization resulted in the following linear equation: ppm NO3-N = 14.8X -45.3. Therefore, there is approximately 15 ppm N mineralized for every 1% OM over 3% soil OM in the experimental fields. In 2018, N-mineralization tests were conducted again and it was estimated on a pounds/acre basis that 16.7 pounds of N are mineralized for each 1% increase in soil organic matter.  

Table 1. 2017 data for crop treatment effects on water infiltration, wind erodible soil fraction and air-dry and field-moist aggregate stability.

Crop Yield and Microbial Activity

 A 10-year integrated crop and livestock study was initiated in 2011 that compared hard red spring wheat grown continuously (HRSW-C) to hard red spring wheat grown in a five-crop rotation (HRSW-R). For the rotation, the sequence of crops consisted of HRSW-R, dual winter and spring cover crops, silage corn, field pea-forage barley mix, and sunflower. Beef cattle are integrated into the systems evaluation due to the importance of grazing to soil biological activity and the potential economic advantages grazing annual forages in an integrated system. As such, the winter triticale-hairy vetch cover crop mix is put up as hay, and the other crops: post-hay harvest 13-specie cover crop, pea-barley mix, and corn are grazing crops for yearling beef steers (Senturklu et al., 2017, 2018, 2019).

A research summary for the first 5-year rotation (2011– 2015) of the 10-year study, provides a description of the research procedures and a brief summary of crop yields, soil organic matter, nitrogen fertility, nutrient cycling, fertilizer reduction, and economics (Landblom et al., 2017). The second 5-year rotation has been negatively affected by hail, wind, and drought resulting in low yields and fluctuating soil microbial properties. Crop yields spring wheat grown continuously (Control) and spring wheat grown in a five-crop rotation for crop years 2016 through 2020 of the 2^nd 5-year crop rotation are shown in Table 2 and compared to the 1^st 5-year rotation. Table 1 also shows the percent of yield of the 2^nd 5-year compared to the 1^st 5-years.

Table 2. 10-Year Cropping System Yields & Percent Difference

2020UPDATE

Cover crop bale grazing after annual forage grazing on yearling steer grazing and feedlot performance, muscling, carcass measurements and carcass value

Results and Discussion

Steer growth for NR and ANN steers, fluctuated during the 177.9-day grazing period. Over the three-year period of the study, hail, wind, exceptional drought, and early deep December snow combined had a negative impact on growing and grazing conditions. Steers that grazed ANN forages before bale grazing were 94.9 lbs. heavier (P = 0.001; Table 2) than NR at the end of bale grazing.

The NR steer gain declined in August and September as the native range forage community matured with advancing season (ADG: NR - 0.67 lbs./day vs Corn grazing – 1.95 lbs./day); however, fall rain stimulated range regrowth and steer gain recovered during Late-September and October. Grazing ANN forage sequence crops maintained ADG at approximately 1.85 lb/day throughout the average 177.9-day grazing season, which is due to annual forage nutrient quality that was consistently greater than NR forage (Table 1).

Cover crop bale grazing gain was greater for ANN steers compared to NR steers (P = 0.008). Gain among ANN compared to NR was 3.04 and 1.77 lb/day, respectively. Given the restricted growth nature commonly associated with extended grazing (NR and ANN), a compensating gain response, such as the responses reported by Senturklu et al. (2017, 2018) and Choat et al. (2003), was expected. Overall, for the entire 221.5-day grazing and bale-grazing period prior to feedlot entry, steer gain and ADG was 376.52 and 1.70; and 463.72 lb and 2.10 lb/day, for the NR and ANN steers, respectively.

Economically important muscle and fat tissues (ribeye muscle area (REA), percent intramuscular fat (IMF), and ending marbling score (MS)) were measured at the end of grazing with ultrasound (Table 2). Ending ribeye muscle area for ANN steers was greater (P=0.001) than the NR steers (12.05 inch vs. 10.99 inch). The muscle relationship between REA and steer ending live weight (REA: CWT) did not differ (P = 0.37). The percent IMF was greater for ANN steers (P = 0.05); however, marbling score was greater for the ANN steers (489 vs 470) but did not differ (P = 0.13).

Feedlot performance between the NR and ANN grazing treatments paralleled one another (Table 3). ANN steers entered the feedlot weighing 1255.06 lb and the NR steers weighed 1168.75 lb (P = 0.04), a margin of 86.31 lb, and ending weight was 1582.04 and 1508.0 lb for the NR and ANN steers, respectively. A difference of 74.0 lb (P = 0.19). For other finishing performance criteria, there were numerical differences; however, none differed significantly. Differences between steer grazing treatments for feedlot gain to feed (G:F) and feed cost/lb of gain were nearly identical ($0.60 vs. $0.59; P = 0.71). In research reported by others, delaying feedlot arrival grazing NR and/or improved tame grass pastures resulted in greater feedlot starting BW and ending slaughter weight compared to steers that did not graze before entering the feedlot (Winterholler et al., 2008; Reuter and Beck, 2013; Lancaster et al., 2014).

Hot carcass weight (P=0.03) and fat depth (P=0.04) were greater for the ANN steers. The ANN treatment steers consistently grazed higher quality forage and growth from cover crop hay increased the potential for fatter carcasses and more overweight carcass discounts. Carcasses from the NR steers had greater dressing percent (P = 0.01), USDA YG (P = 0.01), and REA:HCW ratio (P = 0.007) (Table 4). The muscling relationship identified for the NR steers at the end of grazing remained unchanged by the end of finishing.

Gross carcass value for ANN steers was greater ($2013.93 vs. $1921.67; P = 0.031). Weight margins between the NR and ANN forage groups entering the feedlot do not change appreciably by the end of the finishing period and gross carcass value based on HCW has routinely been greater; however, annual forage farming costs eroded ANN system net return resulting in a $62.26 advantage in favor of the NR system. Overall, comparatively, the two systems were similar and easily adaptable depending on the farm operator’s goals and farming systems. Integrating livestock grazing into cropping systems has many positive aspects and grazing integration is one of the five principles of soil health. Therefore, steer grazing, finishing, and carcass measurement performance are all favorable enhancements following an integrated crop-livestock system.

Literature Cited

Choat, W. T., C. R. Krehbiel, G. C. Duff, R. E. Kirksey, L. M. Lauriault, J. D. Rivera, B. M. Capitan, D. A. Walker, G. D. Donart, and C. L. Goad. 2003. Influence of grazing dormant native range or winter wheat pasture on subsequent finishing cattle performance, carcass characteristics, and ruminal metabolism. J. Anim. Sci. 81:3191-3201.

Lancaster, P. A., C. R. Krehbiel, and G. W. Horn. 2014. A meta-analysis of effects of nutrition and management during the stocker and backgrounding phase on subsequent finishing performance and carcass characteristics. Prof. Anim. Sci. 30:602-612. dx.doi.org/10.15232/ pas.2014-01330

Lewis, J. M., T. J. Klopfenstein, and R. A. Stock. 1990. Effects of rate of gain during winter on subsequent grazing and finishing performance. J. Anim. Sci. 68:2525-2529.

Shain, D. H., T. J. Klopfenstein, R. A. Stock, B. A. Vieselmeyer, and G. E. Erickson. 2005. Evaluation of grazing alternative summer and fall forages in extensive beef cattle production systems. Prof. Anim. Sci. 21:390-402.

Reuter, R. R., and P. A. Beck. 2013. Southern Section Interdisciplinary Beef Cattle Symposium: Carryover effects of stocker cattle systems on feedlot performance and carcass characteristics. J. Anim. Sci. 91:508-515. dx.doi.org/10.2527/jas2012-5527

Senturklu, S., D. G. Landblom, R. Maddock, T. Petry, and S. Paisley. 2017. Effect of retained ownership and vertical integration within an integrated cropping system among yearling steers of differing frame score on feedlot performance, carcass measurements, and systems economics following delayed feedlot entry. Proceedings, West. Sec., ASAS, Vol. 68:203-207. dx.doi.org/10.2527/asasws.2017.0061

Senturklu, S., D. G. Landblom, R. Maddock, T. Petry, C. Wachenheim, and S. Paisley. 2018. Effect of yearling steer sequence grazing of perennial and annual forages in an integrated crop and livestock system on grazing performance, delayed feedlot entry, finishing performance, carcass measurements, and systems economics. J. Anim. Sci. 96(6):2204-2218 https://dx.doi.org/10.1093/ jas/sky150

Winterholler, S. J., D. L. Lalman, M. D. Hudson, C. E. Ward, C. R. Krehbiel, and G. W. Horn. 2008. Performance, carcass characteristics, and economic analysis of calf-fed and wheat pasture yearling   systems in the southern Great Plains. Prof. Anim. Sci. 24:232-238. dx.doi.org/10.1532/ 1080-7446(15)30845-7

Table 1. Nutrient analysis of grazed forages and cover crop bales.

Table 2. Three-year effect of grazing system on yearling steer grazing performance

¹ NR - Native Range; ANN – Grazing Sequence: Native Range, Field Pea-Barley, Unharvested Corn, Cover Crops, and

Cover Crop Bales.

² Average grazing start date each year: NR May - 4, Pea-Barley - July 16, Unharvested Corn – August 17, Cover Crop – October 18, Bale Grazing – November 1, End grazing and transfer to feedlot – December 15.

³ NR and ANN steers were removed from the respective NR and ANN grazing treatments and fed baled cover crop hay for 43.66d.

⁴ Trt – Treatment

⁵ Means with P < 0.05 differ significantly.

⁶ Marbling score: 400 = small; 500 = modest; 600 moderate

Table 3. Systems Three-year feedlot finishing performance of steers placed into feedlot after bale grazing.

¹ NR - Native Range; ANN – Grazing sequence: Native Range, Field Pea-Barley, Unharvested Corn, Cover Crops, and Cover Crop Bales.

² Average grazing start date each year: NR May - 4, Pea-Barley - July 16, Unharvested Corn – August 17, Cover Crop – October 18, Bale Grazing – November 1, End grazing and transfer to feedlot – December 15.

³ NR and ANN steers were removed from the respective NR and ANN grazing treatments and fed cover crop hay for 43.66 d before transfer to the University of Wyoming, SAREC feedlot, Lingle, Wyoming.

⁴ Trt – Treatment

⁵ Means with P < 0.05 differ significantly.

 Table 4. Three-year effect of grazing system on closeout carcass characteristics.

¹ NR - Native Range; ANN – Grazing sequence of Native Range, Field Pea-Barley, Unharvested Corn, Cover Crops, Cover Crop Bales.

² Average grazing start date each year: NR May - 4, Pea-Barley - July 16, Unharvested Corn – August 17, Cover Crop – October 18, Bale Grazing – November 1, End grazing and transfer to feedlot – December 15.

³ NR and ANN steers were removed from the respective NR and ANN grazing treatments and fed cover crop hay for 43.66 d before transfer to the University of Wyoming, SAREC feedlot, Lingle, Wyoming.

⁴ Trt – Treatment

 Means with P < 0.05 differ significantly.

⁶ Marbling score: 400 = small; 500 = modest; 600 moderate.

Table 5. Effect of three-year grazing system and bale grazing on system net return.

¹ NR - Native Range; ANN – Grazing sequence of Native Range, Field Pea-Barley, Unharvested Corn, Cover Crops, Cover Crop Bales.

² Average grazing start date each year: NR May - 4, Pea-Barley - July 16, Unharvested Corn – August 17, Cover Crop – October 18, Bale Grazing – November 1, End bale grazing and transfer to feedlot – December 15.

³ NR and ANN steers were removed from the respective NR and ANN grazing treatments and fed cover crop hay for 43.66 d before transfer to the University of Wyoming, SAREC feedlot, Lingle, Wyoming.

⁴ Trt – Treatment

⁵ Means with P < 0.05 differ significantly.

⁶ Adopted from the North Dakota Farm Business Management Program years 2016, 2017, and 2018.

^7, Native range pasture cost: First half of grazing season, $ ; Second half of grazing season, $

⁸ Cover crop hay price: Year 1 - $65/Ton, Year 2 -$95/Ton, Year 3 - $80/Ton.

⁹ Feedlot cost per steer: From Table 3.

Effect of Extreme Drought on Crop Rotation and Soil Physical and Microbial Property Changes for the period 2016-2020 in Western North Dakota

Results and Discussion

Precipitation during the first five-year rotation was variable, although, generally production was very good. Production for the second five-year period, in which the first four years have been completed, has been very different from the first five years and plagued with multiple environmental insults. The 2016 production year precipitation was considered normal for western ND, however, hail reduced spring wheat yields. The 2017 crop year for the region was rated as an extreme to exceptional drought by the U.S. Drought Monitor (June 27 - Figure 1; August 29 - Figure 2). Regional growing-season precipitation for the 2018 crop improved as indicated by the U.S. Drought Monitor (June 26 - Figure 3; August 28 – Figure 4) and crop yields improved somewhat. The 2019 growing-season precipitation was normal as indicated by the U.S. Drought Monitor (June 25 - Figure 5; August 27 - Figure 6). Fall 2019 was one of unseasonal precipitation in which the total August-September-October rainfall was 13.56 inches. This compares to a more typical fall precipitation of 3.24 inches for the three-month period, or 418% above normal. Sub-soil 2019 moisture carried over into the 2020 cropping season and essentially supported the 2020 crop, because growing season precipitation was diminished as shown in the U.S. Drought Monitor map for June 23, 2020 (Figure 7). The Fall 2020 August precipitation alleviated dry conditions somewhat based on the U.S. Drought Monitor map (August 18 – Figure 8). 

Figure 7

Figure 8

Control and rotation spring wheat yields for the period from 2016 through 2020 are shown in Figure 9. Compared to the initial 2016 crop year, control spring wheat yields were 39.6, -3.14, 16.9, and 1.03%, and rotation spring wheat yields were -6.46, -18.7, 24.5, and -3.74% in 2017, 2018, 2019, and 2020, respectively. Further, comparing the 1^st five years of the study to the 2^nd five years of the study, the effect of a drier cycle on spring wheat and rotation crops was evident. Compared to crop rotation yields for the first five-years (2011-2015), the second five-year yields (2016-2020) were 67.3, 68.4, 88.3, 66.6, 83.3, 69.0, and 66.5% of the first five-years for HRSW-C, HRSW-R, corn, pea-barley mix, cover crop mix, sunflower, and triticale hairy vetch, respectively.

igure 9

Crop yields for rotation crops (triticale-hairy vetch, cover crop, corn, pea-barley, and sunflower) are shown in Figure 10. With the exception of sunflower, which was similar to 2016, other 2020 rotation crop yields were impacted negatively, i.e. pea-barley, corn, cover crop, triticale hair vetch mix yields declined 48.6, 22.4, 73.4, 15.2%, respectively.

Figure 10

Haney test results comparing the 2017-2019-2020 cropping seasons are shown in Table 1. The 2017 drought year began with moist soils. The advancing growing season with significantly reduced precipitation dried soils and inhibited microbial activity. Microbes exist in soil in massive numbers and conform to the soil environment adapting to soil temperature, water content, soil type, and the amounts of available SOM substrate that supports them. Soil organic matter is subject to cropping system diversity ranging from monocultures to multi-crop rotations that supply root and residue substrates for decomposition and mineralization from organic to inorganic states utilized by growing plants. Lack of adequate soil water for soil nutrient solubilization and translocation negatively impacts a very complex biological system of microbial activity, nutrient translocation processes, and plant growth. Table 1 shows the extent of change comparing dry soil in 2017, moist soil in 2019, and somewhat drier soil in 2020 for pH, soluble salt, soil organic matter, CO₂-C release, microbial active carbon percent, organic C: N ratio, organic N: inorganic N ratio, and organic N release. With drying, 2017 soluble salts became more concentrated resulting in a pH decline, more acidic soil conditions, and reduced root activity resulted in SOM decline across all treatments and crops. Microbial active carbon percent, organic C:N ratio, and organic N:inorganic N ratio also declined across treatments and crops except for the dual cover crop and sunflower. Under drought conditions, microbially active carbon was likely being lost and affected soil buffering reactions, and organic N release from soil in all treatments and crops was approximately 200% greater compared to moist conditions in 2019. The return of reduced precipitation in 2020 and effect on soil parameters is summarized in Table 1. Soil drying results in soluble salt concentration and soil pH decline. Soil pH declined among all crops except the pea-barley mixed crop in which pH increased toward neutrality. Drying conditions, for the most part, have negative effects on the soil criterion measured.

Table 1. Haney test microbial analysis for crop years 2017 – 2019 - 2020

While the Haney Test provided results of 24-hour microbial respiration, the PLFA microbial analysis provides measurements of the microbial community and organismal diversity. Microbial contrasts comparing crop years 2017-2019-2020 is shown in Table 2 and summarizes the effect of water stress on total biological biomass, diversity index, total bacterial biomass, total fungi biomass, and abruscular mycorrhizal fungi biomass. Total living microbial biomass expressed in nanograms/gram (ng/g) were rated as slightly above average in 2017 ranging from 1,466 to 2,021 ng/g and rebounded when adequate soil water conditions returned to amounts ranging from 4,462 to 5,325 ng/g that are rated as excellent for healthy soils. Mean difference, when all crops were averaged, shows the biomass resurgence resulting from adequate soil water. Although microbial population biomass declined with the ensuing drought, organism diversity remained largely unchanged ranging from an average 1.49 in 2017 to 1.51 in 2019 on a scale of 0.0 to 2.0. However, comparing 2020 soil microbial diversity to the previous years, there was 39.8% reduction in diversity resulting soil microbial diversity being downgraded from good/very good to average. Given the negative effect reduced soil water has on microbial populations, total bacterial biomass, total fungi biomass, and arbuscular mycorrhizal fungi biomass that rebounded after 2019 soil water increased was severely impacted negatively during the 2020 cropping season. Total fungi biomass was reduced and arbuscular mycorrhizal fungi (AMF) biomass could not detected in samples from cover crop, sunflower, corn, and HRSW-C. Slight quantities of AMF were detected from pea-barley mix fields and HRSW-R fields (Table 2).

Table 2. Phospholipid Fatty Acid (PLFA) microbial analysis results for 2017 – 2019 – 2020

Soil minerals potassium (K), calcium (Ca), aluminum (Al), iron (Fe), sulfur (S), zinc (Zn), manganese (Mn), copper (Cu), magnesium (Mg), and sodium (Na) were similar to the concentration increases measured for the microbial soil characteristics as soil drying advanced resulting in mineral concentration during the 2017 crop year; however, soil mineral concentration declined in 2019 and 2020 compared to 2017 (Table 3) due to soil water dilution and plant utilization. For the 2020 cropping season, mineral concentrations fluctuated slightly, but were largely similar to 2019.

Table 3. Haney test microbial mineral analysis comparing 2017 - 2019 - 2020 crop years

Mineral N Cycling in an Integrated Crop-Grazing System

Results and Discussion 

Changes in mineral N cycling were observed as changes in PMN during the two seasons evaluated thus far in this study (Figures 1 and 2). Potentially mineralizable N is higher in the rotational HRSW (Figure 1) soils due to several factors:

1. A continuous system of diverse crops is growing in the rotational system which then are available for animal forage. This is an ideal system to consider the effects of cover crops in maintaining soil health over a long-term period. Some of the plant species/crops included are normally seeded as grain or forage crops but fall seeded crops such as the triticale/vetch crop also act as cover crops.
2. A diversity of crops that include legumes as forage crops enhance soil N because of the roots and crowns that remain in the soil after harvest/grazing.
3. Animals grazing the crops also distribute dung and urine across the field as they graze which add to the N budget of the soil.
4. These are not normally found in traditional systems similar to the continuous HRSW treatment.
5. In this semi-arid environment, the no-till system also conserves precious soil moisture to be utilized more efficiently by crops and providing a favorable environment for microorganisms in cycling N.

Regression analysis between SOM and PMN thus far indicate that about 8.4 mg N/1% SOM/kg soil are being mineralized across this study (n = 148, R² = 0.21***) Although the R² value for this data is relatively low (0.21), it is highly significant (p > 0.001) due to the large number of data points we have been able to collect to establish a clear relationship of SOM with PMN Early season sampling dates give higher PMN values than later sampling dates because of the effect of the previous season’s crop residues that are decomposing while this season’s crops are still growing and not contributing to the SOM pool (Figure 2).

Summary

Our work continues to show the dynamic nature of N cycling in an integrated crop-grazing system in a semi-arid environment. We have and are continuing to evaluate the soil PMN dynamics for the 2017 and 2018 cropping seasons with mineralization studies that are currently ongoing

Table 1. Soil sampling dates for 2014 and 2016 growing seasons.

Figure 1. Potentially mineralizable N as influenced by cropping treatment for the 2014 (A) and 2016 (B) cropping seasons.   CSW – continuous spring wheat; RSW – rotation spring wheat; NAT – native grassland. Bars with the same small case letters are not significantly different at the P < 0.05 level.

Figure 2. Potentially mineralizable N as influenced by sampling date for the 2014 (A) and 2016 (B) cropping seasons. Bars with the same small case letters are not significantly different at the P < 0.05 level. No significant differences between the 2014 sampling dates.

Integrated Systems Molecular Analysis of Soil Nitrogen Cycling Genes

After water, nitrogen is often the limiting soil nutrient in dry-land agricultural systems and is known to be converted into different forms in the soil by soil bacteria. Therefore, an analysis of the presence and quantity of nitrogen cycling genes was performed on soil samples from the 2019 sampling period. Genes involved in nitrogen fixation (nifH), nitrification (amoA/B), and denitrification (nirS, nirK, and nosZ) were analyzed via qPCR (quantitative Polymerase Chain Reaction). Nitrogen fixation is the conversion of nitrogen gas from the atmosphere into NH₄⁺, nitrification is the eventual conversion of NH₄⁺ to NO₃^-, and denitrification is the conversion of NO₃^- to nitrogen gas (released back to the atmosphere).

Samples for the presence of nitrogen cycling genes were collected on August 27, 2019, at which time spring wheat and rotation crops (pea-barley) had been harvested and corn was being grazed. Cover crops were growing, but not scheduled for grazing until after corn grazing was completed. Essentially, early Fall season. Although analysis is still ongoing, it appears that there is an increased abundance of genes involved in denitrification compared to both nitrogen fixation and nitrification. Suggesting that limited nitrogen nitrification and fixation were possible when soil sampling took place. Future research will look into how nitrogen cycling genes respond using repeated sampling during the full growing season spectrum from May through October.