Maysoon M. Mikha

Nutrient source and tillage impact on corn grain yield and soil properties.

Large amounts of animal manure, particularly poultry litter and dairy manure, are generated in southeastern United States, where corn (Zea mays L.) is also extensively grown. Characterizations of management practices and long-term manure and soil nutrient dynamics are critical. This study examined corn grain yield and soil nutrient status under three nutrient sources (two rates of each) as follows: inorganic fertilizer, poultry litter, and dairy manure compared with a nontreated control under two tillage practices (no-till and incorporated). Treatments were replicated four times in a split-plot design from 2004 to 2007. Soil samples were taken annually in the spring before treatment application to evaluate the status of the residual nutrients in soil. Significant differences in corn grain yield between the two tillage practices (main effect) were observed in all 4 years. The high rate of poultry litter application produced similar grain yield as inorganic fertilizer. However, results from dairy manure were not as consistent as poultry litter. After 4 years of poultry litter application, Mehlich-3 (M-3) phosphorus (P) increased from an initial 31.4 to 63.0 mg kg−1 for the 4.5 Mg ha−1 year−1 rate and to 178 mg kg−1 for the 13.5 Mg ha−1 year−1 rate. More specifically, 5.2 kg ha−1 year−1 of P applied as poultry litter increased soil M-3 P by 1 mg kg−1 after 4 years of application. Results indicated that poultry litter is a primary fertilizer at the rate of 13.5 Mg ha−1 applied in four consecutive years on a silt loam soil-produced corn grain yields similar to inorganic fertilizer under both no-till and incorporated systems and did not result in residual soil test P, Cu, and zinc levels considered to be harmful to surface water or cropping systems.

Effect of nitrogen fertilization and cover cropping systems on sorghum grain characteristics.

Cover crop treatments and nitrogen (N) fertilization rates were investigated for their impact on sorghum grain quality attributes. Sorghum was planted in field plots treated with differing cover cropping systems and fertilization rates. The size (weight and diameter) and hardness of the kernels were influenced by both the cover crop and N rates. The protein content increased as the N rate increased and also with the addition of cover crops to the system. The protein digestibility values and starch granule size distributions were not affected by N rate or the cover cropping treatments. Soil properties were tested to determine relationships with grain quality attributes. The utilization of cover crops appears to increase the protein content without causing a deleterious effect on protein digestibility. The end-product quality is not hampered by the use of beneficial cropping systems necessary for sustainable agriculture.

Switchgrass Biochar Effects on Plant Biomass and Microbial Dynamics in Two Soils from Different Regions

Abstract Biochar amendments to soils may alter soil function and fertility in various ways, including through induced changes in the microbial community. We assessed microbial activity and community composition of two distinct clayey soil types, an Aridisol from Colorado (CO) in the U.S. Central Great Plains, and an Alfisol from Virginia (VA) in the southeastern USA following the application of switchgrass ( Panicum virgatum ) biochar. The switchgrass biochar was applied at four levels, 0%, 2.5%, 5%, and 10%, approximately equivalent to biochar additions of 0, 25, 50, and 100 t ha −1 , respectively, to the soils grown with wheat ( Triticum aestivum ) in an eight-week growth chamber experiment. We measured wheat shoot biomass and nitrogen (N) content and soil nutrient availability and N mineralization rates, and characterized the microbial fatty acid methyl ester (FAME) profiles of the soils. Net N mineralization rates decreased in both soils in proportion to an increase in biochar levels, but the effect was more marked in the VA soil, where net N mineralization decreased from −2.1 to −38.4 mg kg −1 . The 10% biochar addition increased soil pH, electrical conductivity, Mehlich- and bicarbonate-extractable phosphorus (P), and extractable potassium (K) in both soil types. The wheat shoot biomass decreased from 17.7 to 9.1 g with incremental additions of biochar in the CO soil, but no difference was noted in plants grown in the VA soil. The FAME recovery assay indicated that the switchgrass biochar addition could introduce artifacts in analysis, so the results needed to be interpreted with caution. Non-corrected total FAME concentrations indicated a decline by 45% and 34% with 10% biochar addition in the CO and VA soils, respectively, though these differences became nonsignificant when the extraction efficiency correction factor was applied. A significant decline in the fungi:bacteria ratio was still evident upon correction in the CO soil with biochar. Switchgrass biochar had the potential to cause short-term negative impacts on plant biomass and alter soil microbial community structure unless measures were taken to add supplemental N and labile carbon (C).

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.

Agricultural Management and Soil Carbon Dynamics: Western U.S. Croplands

Maintaining or increasing SOC has been a challenge in the western U.S. because crop biomass yields and C inputs are often lower in arid and semiarid regions than in humid regions due to limited precipitation and shorter growing season. As a result, it often takes a long time to increase SOC storage. Novel management practices, such as reduced tillage, continuous cropping, and increased cropping intensity, can increase SOC storage compared with conventional systems. This review of recent literature indicates that SOC storage studies in the western U.S. are still quite limited. The purpose of this chapter is to provide a short review and update of potential crop management practices that have had beneficial or detrimental effects on soil C storage in western U.S. croplands.

Soil Nutrients Status after Fifty Years of Tillage and Nitrogen Fertilization

ABSTRACT Long-term studies are valuable in assessing the impact of crop management practices on soil sustainability and function. This study used two calculation scenarios, fixed depth and Equivalent Soil Mass (ESM) to assess (i) soil nutrient status and (ii) soil organic carbon (SOC) after 50 years of nitrogen (N) fertilizer application rates (0, 22, 45, and 67 kg N ha−1) and tillage [clean tillage (CT), reduced tillage (RT), and no-tillage (NT)] in a dryland winter wheat-sorghum-fallow cropping system. The soil organic matter (SOM) content increased by 33% with NT and RT compared with CT. The SOC at 0–30 cm was 39% greater than 30–60 cm depth with both fixed depth and ESM calculations. Soil nutrient specifically soil calcium (Ca), magnesium (Mg), and phosphorus (P) associated with N rates were no different than the control. Crop nutrient removal may eventually reduce soil nutrient contents with only N application. Nutrient addition specifically P should be considered in the future.

Incorporation of Biochar Carbon into Stable Soil Aggregates: The Role of Clay Mineralogy and Other Soil Characteristics

Aggregation and structure play key roles in water-holding capacity and stability of soils. In this study, the incorporation of carbon (C) from switchgrass biochar into stable aggregate size fractions was assessed in an Aridisol (from Colorado, USA) dominated by 2:1 clays and an Alfisol (from Virginia, USA) containing weathered mixed 1:1 and 2:1 mineralogy, to evaluate the effect of biochar addition on soil characteristics. The biochar was applied at 4 levels, 0, 25, 50, and 100 g kg−1, to the soils grown with wheat in a growth chamber experiment. The changes in soil strength and water-holding capacity using water release curves were measured. In the Colorado soil, the proportion of soil occurring in large aggregates decreased, with concomitant increases in small size fractions. No changes in aggregate size fractions occurred in the Virginia soil. In the Colorado soil, C content increased from 3.3 to 16.8 g kg−1, whereas in the 2 000 µm fraction. The greatest increase (from 6.2 to 22.0 g kg−1) occurred in the 53–250 µm fraction. The results indicated that C was incorporated into larger aggregates in the Virginia soil, but remained largely unassociated to soil particles in the Colorado soil. Biochar addition had no significant effect on water-holding capacity or strength measurements. Adding biochar to more weathered soils with high native soil organic content may result in greater stabilization of incorporated C and result in less loss because of erosion and transport, compared with the soils dominated by 2:1 clays and low native soil organic content.

Agricultural Management and Soil Carbon Dynamics

Maintaining or increasing SOC has been a challenge in the western U.S. because crop biomass yields and C inputs are often lower in arid and semiarid regions than in humid regions due to limited precipitation and shorter growing season. As a result, it often takes a long time to increase SOC storage. Novel management practices, such as reduced tillage, continuous cropping, and increased cropping intensity, can increase SOC storage compared with conventional systems. This review of recent literature indicates that SOC storage studies in the western U.S. are still quite limited. The purpose of this chapter is to provide a short review and update of potential crop management practices that have had beneficial or detrimental effects on soil C storage in western U.S. croplands.

Chapter 5 – Agricultural Management and Soil Carbon Dynamics: Western U.S. Croplands

Maintaining or increasing SOC has been a challenge in the western U.S. because crop biomass yields and C inputs are often lower in arid and semiarid regions than in humid regions due to limited precipitation and shorter growing season. As a result, it often takes a long time to increase SOC storage. Novel management practices, such as reduced tillage, continuous cropping, and increased cropping intensity, can increase SOC storage compared with conventional systems. This review of recent literature indicates that SOC storage studies in the western U.S. are still quite limited. The purpose of this chapter is to provide a short review and update of potential crop management practices that have had beneficial or detrimental effects on soil C storage in western U.S. croplands.

Predicting Winter Wheat Yield Loss from Soil Compaction in the Central Great Plains of the United States

Adoption of methods to minimize the effects of soil compaction on crop production by farmers has been slow. Often farmers do not equate degradation of soil physical properties with reduction in crop yield. The objective of this study was to determine the potential yield loss caused by degradation of soil physical quality due to compaction. Soil conditions and winter wheat (Triticum aestivum L.) yields were observed on the Alternative Crops Rotation study at Akron, Colorado in 1996 and 1997. Changes in soil physical properties were determined by observing changes in the soil Least Limiting Water Range (LLWR), which includes limitations of water holding capacity, soil strength and soil aeration, on crop production. Grain yield decreased approximately 1,000 kg ha–1 per 0.1 unit decrease in LLWR, showing that soil compaction can cause serious yield reductions if not managed properly. Soil compression curves were developed to help predict the amount of soil compaction, and subsequent yield loss, to be expected with wheel traffic at various tire pressures and soil moisture conditions. Methods such as controlled wheel traffic or the use of low-pressure tires should be used to reduce soil compaction and maintain soil productivity.