Merle F. Vigil

Cropping System Influence on Planting Water Content and Yield of Winter Wheat

wheat yields were reduced by 79 kg ha 1 for every centimeter that soil water at wheat planting was reduced by Many dryland producers in the central Great Plains of the USA sunflower (Helianthus annuus L.) ahead of wheat in express concern regarding the effect that elimination of fallow has on soil water content at winter wheat (Triticum aestivum L.) planting rotation. In southwestern Kansas, Norwood (2000) simiand subsequent yields. Our objectives were to quantify cropping syslarly showed lower winter wheat yields when the previtem effects (fallow weed control method and crop sequence), including ous crop was sunflower or soybean compared with corn corn (Zea mays L.) (C) and proso millet (Panicum miliacium L.) (M), or grain sorghum [Sorghum bicolor (L.) Moench]. These on soil water at winter wheat planting and subsequent grain yield, and reductions in wheat yield were related to lower soil to determine the frequency of environmental conditions which would water at planting. Lyon et al. (1995) showed that soil cause wheat yield to drop below 2500 kg ha 1 for various cropping water at planting was strongly correlated with yield of systems. Crop rotations evaluated from 1993 through 2001 at Akron, short season summer crops [pinto bean (Phaseolus vulCO, were W-F, W-C-F, W-M-F, and W-C-M (all no-till), and W-F garis L.), proso millet] but only weakly related to yield (conventional till). Yields were correlated with soil water at planting: of long season summer crops (sunflower, grain sorghum, kg ha 1 373.3 141.2 cm (average and wet years); kg ha 1 897.9 39.7 cm (dry years). Increasing cropping intensity to two corn). They attributed this result in part to shorter seacrops in 3 yr had little effect on water content at wheat planting and son crops having more soil water available at the critical subsequent grain yield, while continuous cropping and elimination of reproductive growth stage than longer season crops, fallow reduced soil water at planting by 11.8 cm and yields by 450 which used much of the initial soil water for stover to 1650 kg ha 1, depending on growing season precipitation. No-till production and did not have it available for grain develsystems, which included a 12to 15-mo fallow period before wheat opment. planting nearly always produced at least 2500 kg ha 1 of yield under In addition to differences in previous crop water use, normal to wet conditions, but no cropping system produced 2500 kg soil water content at wheat planting can also be affected ha 1 under extremely dry conditions. by differences in tillage and crop residue effects on precipitation storage efficiency. Precipitation storage efficiency increases as tillage is reduced during the sumT traditional wheat–fallow production system used mer fallow period before wheat planting (Smika and in the central Great Plains of the USA was develWicks, 1968; Tanaka and Aase, 1987; Norwood, 1999). oped in the 1930s as a strategy to minimize incidence of Crop residues reduce soil water evaporation by shading crop failures resulting from erratic precipitation (Hinze the soil surface and reducing convective exchange of and Smika, 1983). The use of herbicides to control weeds water vapor at the soil–atmosphere interface (Greb et in this system reduced or eliminated tillage, and led to al., 1967; Aiken et al., 1997; Van Doren and Allmaras, greater precipitation storage efficiencies, such that more 1978). Additionally, reducing tillage and maintaining frequent cropping could be successfully employed (Halsurface residues reduce precipitation runoff and invorson and Reule, 1994; Peterson et al., 1993; Anderson crease infiltration, thereby increasing precipitation storet al., 1999; Norwood et al., 1990; Smika, 1990; Farahani age efficiency (Unger and Stewart, 1983). et al., 1998). Both producers and agricultural lenders would like While more intensive cropping is gradually replacing to have a means of assessing the risk level that might W-F in the central Great Plains, many producers still be incurred in moving from conventional wheat–fallow express concern regarding the effect that more frequent production systems to more intensively cropped no-till cropping has on soil water content at planting and subsesystems. Part of that risk assessment involves quantifyquent winter wheat yields. Previous research has shown ing the effects of cropping system on wheat yields. Thererelationships between available soil water and yield of fore, the objectives of this study were to (i) quantify some crops. Nielsen et al. (1999) reported that winter effects of cropping system (crop sequence and fallowseason weed-control method [i.e., tillage vs. no-till]) on D.C. Nielsen, M.F. Vigil, R.A. Bowman, and J.G. Benjamin, USDAsoil water content at winter wheat planting and subseARS, Central Great Plains Res. Stn., 40335 County Road GG, Akron, quent effects on grain yield, and (ii) determine freCO 80720; R.L. Anderson, USDA-ARS, Northern Grain Insects Res. quency of environmental conditions that cause wheat Lab., 2923 Medary Ave., Brookings SD 57006; and A.D. Halvorson, USDA-ARS, Soil–Plant–Nutrient Research Unit, P.O. Box E, 301 S. Howes, Ft. Collins, CO 80522. Received 21 Jan. 2002. *Corresponding Abbreviations: CT, conventional tillage; W-C-F, wheat–corn–fallow; author (dnielsen@lamar.colostate.edu). W-C-M, wheat–corn–millet; W-F, wheat–fallow; W-M-F, wheat–millet– fallow; NT, no-till. Published in Agron. J. 94:962–967 (2002).

Quantifying effects of soil conditions on plant growth and crop production

Soil management decisions often are aimed at improving or maintaining the soil in a productive condition. Several indicators have been used to denote changes in the soil by various management practices, but changes in bulk density is the most commonly reported factor. Bulk density, in and of itself, gives little insight on the underlying soil environment that affects plant growth. We investigated using the Least Limiting Water Range (LLWR) to evaluate changes in the soil caused by soil management. The LLWR combines limitations to root growth caused by water holding capacity, soil strength and soil aeration into a single number that can be used to determine soil physical improvement or degradation. The LLWR appeared to be a good indicator of plant productivity when the full potential of water holding capacity on available water can be realized, such as with wheat (Triticum aestivum, L.) grown in a no-till system when the wheat followed a fallow period. A regression of wheat yield to LLWR gave an r 2 of 0.76. The LLWR was a poorer indicator of plant productivity when conditions such as low total water availability limited the expression of the potential soil status on crop production. Dryland corn (Zea mays, L.) yields were more poorly correlated with LLWR (r 2 =0.18), indicating that, under dryland conditions, in-season factors relating to water infiltration may be more important to corn production than water holding capacity. An improved method to evaluate in-season soil environmental dynamics was made by using Water Stress Day (WSD). The WSD was calculated by summing the differences of actual water contents in the field from the limits identified by the LLWR during the growing season. A regression of irrigated corn yield with LLWR as the soil indicator of the soil environment resulted in an r 2 of 0.002. A regression of the same yield data with WSD as the indicator of the soil environment resulted in an r 2 of 0.60. We concluded that the LLWR can be a useful measure of management effects on soil potential productivity. Soil management practices that maximize the LLWR can maximize the potential of a soil for crop production. Knowledge of the LLWR for a soil can help the farm manager optimize growing conditions by helping schedule irrigation and for making tillage decisions. The WSD, calculated from the LLWR and in-season water dynamics, allows us to evaluate changes in the

Cropping system influences on soil chemical properties and soil quality in the Great Plains

Soil management and cropping systems have long-term effects on agronomic and environmental functions. This study examined the influence of contrasting management practices on selected soil chemical properties in eight long-term cropping system studies throughout the Great Plains and the western Corn Belt. For each study, soil organic C (SOC), total N (TN), particulate organic matter (POM), inorganic N, electrical conductivity (EC), and soil pH were evaluated at 0‐7.5, 7.5‐15, and 15‐30 cm within conventional (CON) and alternative (ALT) cropping systems for 4 years (1999‐2002). Treatment effects were primarily limited to the surface 7.5 cm of soil. No-tillage (NT) and/or elimination of fallow in ALT cropping systems resulted in significantly (P < 0.05) greater SOC and TN at 0‐7.5 cm within five of the eight study sites [Akron, Colorado (CO); Bushland, Texas (TX); Fargo, North Dakota (ND); Mandan, ND; and Swift Current, Saskatchewan (SK), Canada]. The same pattern was observed with POM, where POM was significantly (P < 0.05) greater at four of the eight study sites [Bushland, TX, Mandan, ND, Sidney, Montana (MT), and Swift Current, SK]. No consistent pattern was observed with soil EC and pH due to management, although soil EC explained almost 60% of the variability in soil NO3-N at 0‐7.5 cm across all locations and sampling times. In general, chemical soil properties measured in this study consistently exhibited values more conducive to crop production and environmental quality in ALT cropping systems relative to CON cropping systems.

Measuring bacterial and fungal substrate-induced respiration in dry soils

Abstract The substrate-induced respiration inhibition (SIRIN) method of Anderson and Domsch for partitioning bacterial and fungal contributions to soil respiration was modified for application to dry soils. This new method also provided a comparative basis when measuring SIRIN in soils of different moisture contents. Soil was incubated under optimum moisture conditions (55% water-filled pore space) to maximize microbial activity and to ensure homogeneous incorporation of substrate and inhibitors into soil. Soil samples were packed to a uniform bulk density prior to measurement of CO2 evolution by gas chromatography. Glucose (3 mg g−1) was added together with streptomycin (0.5 or 1.0 mg g−1) and/or cycloheximide (15 mg g−1) for selective respiratory inhibition. The procedure included conditioning for 16 h at 4°C, followed by 1.5-h equilibration and 2-h incubation. The method yielded consistent and reproducible CO2 respiration measurements for soils from a semi-arid region having gravimetric moisture contents ranging between 7.5 and 23.2%. Method sensitivity was not sufficient to detect variations in the fungal-to-bacterial ratio due to management practice for the soil under study. Measured fungal-to-bacterial ratios of 29:1 and 15:1, for conventionally and no-till managed soil, were not significantly different at a probability level of 5%.

Skip-Row Planting Patterns Stabilize Corn Grain Yields in the Central Great Plains

The highly variable climate of the central Great Plains makes dryland corn (Zea mays) production a risky enterprise. Twenty-three field trials were conducted across the central Great Plains from 2004 through 2006 to quantify the effect of various skip-row planting patterns and plant populations on grain yield in dryland corn production. A significant planting pattern by plant population interaction was observed at only one of 23 trials, suggesting that planting pattern recommendations can be made largely irrespective of plant population. In trials where skip-row planting patterns resulted in increased grain yields compared to the standard planting pattern treatment (every row planted using a 30-inch row spacing), the mean grain yield for the standard planting treatment was 44 bu/acre. In those trials where skip-row planting resulted in decreased grain yield compared to the standard planting pattern, the mean yield was 135 bu/acre. The plant two rows, skip two rows planting pattern is recommended for riskaverse growers in the central Great Plains where field history or predictions suggest likely grain yields of 75 bu/acre or less. Planting one row and skipping one row is recommended for growers with moderate risk-aversion and likely yield levels of 100 bu/acre or less.

A comparison of corn (Zea mays L.) residue and its biochar on soil C and plant growth.

In order to properly determine the value of charring crop residues, the C use efficiency and effects on crop performance of biochar needs to be compared to the un-charred crop residues. In this study we compared the addition of corn stalks to soil, with equivalent additions of charred (300 °C and 500 °C) corn residues. Two experiments were conducted: a long term laboratory mineralization, and a growth chamber trial with proso millet plants. In the laboratory, we measured soil mineral N dynamics, C use efficiency, and soil organic matter (SOM) chemical changes via infrared spectroscopy. The 300 °C biochar decreased plant biomass relative to a nothing added control. The 500°C biochar had little to no effect on plant biomass. With incubation we measured lower soil NO3 content in the corn stalk treatment than in the biochar-amended soils, suggesting that the millet growth reduction in the stalk treatment was mainly driven by N limitation, whereas other factors contributed to the biomass yield reductions in the biochar treatments. Corn stalks had a C sequestration use efficiency of up to 0.26, but charring enhanced C sequestration to values that ranged from 0.64 to 1.0. Infrared spectroscopy of the soils as they mineralized showed that absorbance at 3400, 2925-2850, 1737 cm-1, and 1656 cm-1 decreased during the incubation and can be regarded as labile SOM, corn residue, or biochar bands. Absorbances near 1600, 1500-1420, and 1345 cm-1 represented the more refractory SOM moieties. Our results show that adding crop residue biochar to soil is a sound C sequestration technology compared to letting the crop residues decompose in the field. This is because the resistance to decomposition of the chars after soil amendment offsets any C losses during charring of the crop residues.

Great Plains cropping system studies for soil quality assessment

Interactions between environmental conditions and management practices can significantly affect soil function. Soil quality assessments may improve our understanding of how soils interact with the hydrosphere and atmosphere. This information can then be used to develop management practices that improve the capacity of the soil to perform its various functions and help identify physical, chemical, and biological soil attributes to quantify the present state of a soil and detect changes resulting from management. In protocols established by the Great Plains cropping system network, sampling and testing procedures were selected to identify physical, chemical, and biological soil attributes responsive to management that may serve as useful indicators in assessing the effects of management on the soil resource. Eight existing long-term studies from throughout the Great Plains in the central USA were used to make these assessments because, (1) many years are required for certain soil properties to change measurably; (2) annual weather causes variation in system performance; and (3) the soil pools of interest are spatially variable. This paper includes detailed descriptions of the treatments and sites, and both long-term and short-term (1999–2002) data on precipitation, temperature, and yields for each location.

Manure and tillage use in remediation of eroded land and impacts on soil chemical properties

Soil loss through wind and water erosion is an ongoing problem in semiarid regions. A thin layer of top soil loss over a hectare of cropland could be corresponding to tons of productive soil loss per hectare. The objectives of this study were to evaluate the influence of beef feedlot manure, tillage and legume grass mixtures on changes in soil quality and nutrient components. The study was initiated in 2006 on an eroded site near Akron, Colorado, on a Norka-Colby very-fine sandy loam (fine-silty, mixed, mesic, Aridic, Argiustolls). Tillage treatments were no-tillage, shallow tillage (sweeps operations with V-blade) and deep tillage (DT; moldboard plow operations). In one set of plots, DT was implemented biannually (DT-2); and in another set the DT was done once at the initiation of the experiment in 2006. Amendments consisted of beef manure and urea (46-0-0), N fertilizer. Both amendments were added at low and high rates. A control treatment, with no fertilizer or manure added, was included with no-tillage and shallow tillage only. Six years of manure addition and tillage significantly altered soil chemical properties compared with fertilizer and grass legume mixtures. Across all the tillage treatments, at the 0–30 cm depth, soil pH from 2006 to 2012, was reduced 1.8 fold with high-manure compared with high-fertilizer treatment. Soil EC, Na, and SAR increased by 2.7 fold while soil P increase by 3.5 fold with high-manure treatment compared with low-manure from 2006 to 2012 across all the tillage treatments at the surface 0–30 cm. Soil organic carbon associated with high-manure was 71% higher than low-manure and 230% higher than high-fertilizer treatments in the 0–60 cm depth. Similar patterns were observed with soil total N. Overall, manure amendments greatly improved the soil nutrient status on this eroded site. However, the legume grass mixtures showed little effect on improving soils chemical properties. The micronutrients supplied by manure improved the soil nutrient status compared with inorganic fertilizer, the grass, and the grass-legume treatments. We concluded that more than six years are needed to measure significant improvements in soil quality from specific treatments, specifically fertilizer, grasses, and grass-legume mixtures in such eroded crop land.

Cover Crop and Irrigation Effects on Soil Microbial Communities and Enzymes in Semiarid Agroecosystems of the Central Great Plains of North America

Cover crops can have beneficial effects on soil microbiology by increasing carbon (C) supply, but these beneficial effects can be modulated by precipitation conditions. The objective of this study was to compare a fallow-winter wheat (Triticum aestivum L.) rotation to several cover crop-winter wheat rotations under rainfed and irrigated conditions in the semiarid US High Plains. Experiments were carried out at two sites, Sidney in Nebraska, and Akron in Colorado, USA, with three times of soil sampling in 2012–2013 at cover crop termination, wheat planting, and wheat maturity. The experiments included four single-species cover crops, a 10-species mixture, and a fallow treatment. The variables measured were soil C and nitrogen (N), soil community structure by fatty acid methyl ester (FAME) profiles, and soil β-glucosidase, β-glucosaminidase, and phosphodiesterase activities. The fallow treatment, devoid of living plants, reduced the concentrations of most FAMEs at cover crop termination. The total FAME concentration was correlated with cover crop biomass (R = 0.62 at Sidney and 0.44 at Akron). By the time of wheat planting, there was a beneficial effect of irrigation, which caused an increase in mycorrhizal and protozoan markers. At wheat maturity, the cover crop and irrigation effects on soil FAMEs had subsided, but irrigation had a positive effect on the β-glucosidase and phosphodiesterase activities at Akron, which was the drier of the two sites. Cover crops and irrigation were slow to impact soil C concentration. Our results show that cover crops had a short-lived effect on soil microbial communities in semiarid wheat-based rotations and irrigation could enhance soil enzyme activity. In the semiarid environment, longer time spans may have been needed to see beneficial effects of cover crops on soil microbial community structure, soil enzyme activities, and soil C sequestration.

Mid-Infrared and Near-Infrared Calibrations for Nutritional Parameters of Triticale (Triticosecale) and Pea (Pisum sativum)

The objective of this study was to develop Fourier transformed mid-infrared (MidIR) and near-infrared (NIR) calibrations for acid detergent fiber (ADF), neutral detergent fiber (NDF), and total nitrogen in triticale, peas, and triticale/pea mixtures. Heterogeneous calibration-validation combinations were also tested for calibration quality. The forage samples were collected from forage plots grown following millet or wheat. Other factors included population density, forage mixtures, and nitrogen fertilizer rate. Total N always achieved a better validation R(2) than ADF and NDF, regardless of the sample set or spectral range. The ADF and NDF could not be predicted well with heterogeneous calibration/validation sets, with the exception of ADF predicted by the pea/triticale mixture in the MidIR. Using whole sample sets resulted in better predictive calibrations for the fiber analytes for both the MidIR and the NIR. This study shows that MidIR compares well with NIR for the development of ADF and total N calibrations in forages. The NIR and MidIR are both useful as quick methods for measuring total N, and they show promise for measuring ADF and total N in forage samples, but performance with NDF was less satisfactory.