Martha Mamo

Soil organic carbon: The value to soil properties

Maintaining or improving soil properties is becoming increasingly important to sustain modern agriculture under increasing demands to preserve biodiversity and environmental quality. Enhancing the inherent capacity of a soil to buffer changes against anthropogenic stresses and extreme climatic events such as droughts, intense rainstorms, heat waves, and floods is also a priority. Managing soil organic carbon (SOC) through optimized management practices is one strategy to enhance soil ecosystem services. Increasing organic C storage in the soil not only sequesters atmospheric C but often enhances soil physical, chemical, and biological processes and properties. Soil organic C has been widely discussed in terms of C sequestration, but its benefits on soil processes and properties have received less attention in recent years. Thus, this article discusses (1) the value of SOC to soil properties and (2) potential for increasing SOC through management. SOIL CARBON DYNAMICS The balance between C inputs and outputs is important to SOC change. Inputs include aboveground and belowground crop residues, animal manure, compost, and others, whereas outputs are losses through water and wind erosion, gas fluxes associated with microbial and plant respiration, and deep leaching. How fast residues decompose following the well-known exponential decay function depends…

Patch burning: implications on water erosion and soil properties.

Patch burning can be a potential management tool to create grassland heterogeneity and enhance forage productivity and plant biodiversity, but its impacts on soil and environment have not been widely documented. In summer 2013, we studied the effect of time after patch burning (4 mo after burning [recently burned patches], 16 mo after burning [older burned patches], and unburned patches [control]) on vegetative cover, water erosion, and soil properties on a patch-burn experiment established in 2011 on a Yutan silty clay loam near Mead, NE. The recently burned patches had 29 ± 8.0% (mean ± SD) more bare ground, 21 ± 1.4% less canopy cover, and 40 ± 11% less litter cover than older burned and unburned patches. Bare ground and canopy cover did not differ between the older burned and unburned patches, indicating that vegetation recovered. Runoff depth from the older burned and recently burned patches was 2.8 times (19.6 ± 4.1 vs. 7.1 ± 3.0 mm [mean ± SD]) greater than the unburned patches. The recently burned patches had 4.5 times greater sediment loss (293 ± 89 vs. 65 ± 56 g m) and 3.8 times greater sediment-associated organic C loss (9.2 ± 2.0 vs. 2.4 ± 1.9 g m) than the older burned and unburned patches. The recently burned patches had increased daytime soil temperature but no differences in soil compaction and structural properties, dissolved nutrients, soil C, and total N concentration relative to older burned and unburned patches. Overall, recently burned patches can have reduced canopy and litter cover and increased water erosion, but soil properties may not differ from older burn or unburned patches under the conditions of this study.

Manure Phosphorus Fractions: Development of Analytical Methods and Variation with Manure Types

Abstract Manure phosphorus (P) extraction and storage procedures were evaluated, and manure types were characterized for extractable P. The objectives of this research were to evaluate manure P extraction and sample storage procedures and to characterize manure types for water‐extractable P (WEP) and NaHCO3 P (BiEP). Manure P was extracted at dry matter–to–water extraction ratios of 0.5 g/200 mL, 2 g/200 mL, 2 g/20 mL, and 20 g/200 mL. Shaking times of 0.5 h, 1 h, or 2 h were evaluated along with filter paper types (Whatman No. 42, Whatman No. 40, and 0.45‐µm). Single or sequential extractions and repeated extractions with water or NaHCO3 were also compared on various manure sources. Manure types were treated as replications in the analysis of variance to reduce the probability of making a Type I error in applying the results to diverse manure types. Dry matter–to–water extraction ratios more concentrated than 1 g/100 mL removed less P than extraction at 1 g/200 mL, which removed a similar percentage of total P (TP) as 0.5 g/200 mL ratio. A single extraction with a 1 g/200 mL or more dilute ratio with 1 h of shaking time was found to give a good estimate of extractible P. Extracted manure P was similar for three sequential extractions of 1 g/100 mL dilution ratio compared to one extraction with 1 g/300 mL. Filter paper type did not affect the amount of P extracted. Phosphorus extraction was more consistent with samples stored dry as compared to refrigerated or frozen conditions. Extractible P in swine manure, as a percentage of TP, was more than for other manure types.

Cultivation Effects on Organic Matter Concentration and Infiltration Rates of Two Creeping Bentgrass ( Agrostis stolonifera L.) Putting Greens

Soil cultivation is commonly used to manage organic matter (OM) accumulation in golf course putting greens. Our objectives were to determine: (i) if hollow-tine cultivation is more effective than solidtine cultivation at managing OM and water infiltration, (ii) if venting methods are effective at managing OM and water infiltration, and (iii) if venting alters or interacts with effects of earlyor late-season cultivation. The study was a 3 ́ 5 factorial repeated on two ‘Providence’ creeping bentgrass (Agrostis stolonifera L.) research putting greens. Tine treatments were hollow-tine, solid-tine, or no-tine cultivation. Venting treatments were Hydroject, PlanetAir, quad needle tine, bayonet tine, or no venting. Soil samples were collected and analyzed for OM content using loss on ignition. Water infiltration rates were determined in situ. After 2 years, there were few consistent differences found among the tine and venting treatments, and there were no significant interactions regarding OM concentration. This response was attributed to the small amount of surface area impacted by cultivation and to the equalization of topdressing quantity across all treatment combinations. Hollowtine and solid-tine cultivation increased infiltration compared with no cultivation. In general, Hydroject treatments increased water infiltration rates more than all other venting treatments regardless of tine treatment. Organic matter accumulation in creeping bentgrass putting greens has been a concern since the innovation of sand-based root zones (Gaussoin et al., 2013). Accumulation of OM can increase thatch in a putting green, creating a soft, saturated surface that results in decreased playability (Glasgow et al., 2005). Equipment and foot traffic can also cause surface imperfection (e.g., ruts, scalping, and foot imprints) on putting greens with high OM content (Oatis, 2010). Excessive OM decreases water infiltration rates and increases surface water retention (Hurto et al., 1980). Excess surface water retention for extended periods decreases gas exchange (O2, CO2, CH4) between the soil and atmosphere, which can have a negative impact on turfgrass growth (Carrow et al., 2001; Hillel, 2004). Published in Applied Turfgrass Science DOI 10.2134/ATS-2014-0032-RS

Vegetation and Soil Responses to Concrete Grinding Residue Application on Highway Roadsides of Eastern Nebraska

As a precautionary principle, the National Pollutant Discharge Elimination System (NPDES) permit establishes that the primary pollutant in concrete grinding residue (CGR) is its alkalinity and restricts CGR roadside discharge to 11 Mg ha or the agronomic liming rate, whichever is lower. We evaluated the effect of CGR application on roadside soil chemical properties, existing vegetation, and rainfall runoff. Five CGR rates (0, 11, 22, 45, and 90 dry Mg ha) were tested on roadsides slopes at two different locations in eastern Nebraska. Vegetation, soil, and runoff characteristics were evaluated before CGR application and 30 d and 1 yr after CGR application. Soil pH of control plots averaged 8.3 and 8.5 for each site respectively, across depths and slope positions, thus not requiring any liming for agronomic purposes. Soil electrical conductivity (EC, 1:1) averages of control plots were 0.79 and 1.24 dS m across depths and slope positions. In the short term (30 d) the highest CGR application affected the 0- to 7.5-cm soil depth by increasing soil extractable Ca (21 and 25% for each site, respectively), soil pH (0.2, south site), and soil EC (0.2 dS m) compared with the control. However, these changes in soil did not persist 1 yr after CGR application. The pH buffering capacity of soil prevented post-CGR-application pH from exceeding 8.9, even at the highest application rate. Application of CGR did not produce any differences in biomass production, botanical composition, and runoff characteristics at either site. From our study, CGR up to ?90 dry Mg ha-about the amount produced during diamond grinding operations-can be one-time applied to roadside soils of similar characteristics on already established vegetation.

Roles for Herbaceous and Grain Legumes, Kraal Manure, and Inorganic Fertilizers for Soil Fertility Management in Eastern Uganda

Grain sorghum [Sorghum bicolor (L.) Moenich] is an important food crop in semi-arid areas of sub-Saharan Africa. Crop yields are generally low and declining partly due to low soil fertility. Therefore on-farm research was conducted on 108 farms at three locations over 3 years to evaluate alternative low-input strategies for soil fertility improvement in sorghum-based cropping systems. The strategies were use of herbaceous legumes in improved fallow, a grain legume in rotation with sorghum, use of cattle manure, and application of low levels of N and P fertilizers. Mucuna (Mucuna pruriens) on average produced 7 t ha–1 of aboveground dry matter containing 160 kg N ha–1. Application of 2.5 t ha–1 of kraal manure and a combination of 30 kg N and 10 kg P ha–1 both increased grain yield by a mean of 1.15 t ha–1. A combination of 2.5 t ha–1 manure with 30 kg N ha–1 increased grain yield by 1.4 t ha–1 above the farmer practice (1.1 t ha–1 grain). The increase in sorghum grain yield in response to 30 kg N ha–1, to a Mucuna fallow, and to a rotation with cowpea (Vigna unguiculata) was 1.0, 1.4, and 0.7 t ha–1, respectively. These alternative strategies were found to be cost-effective in increasing sorghum yield in the predominantly smallholder agriculture where inorganic fertilizer is not used. Results of the study indicated that on-farm profitability and food security could be improved through integration of inorganic fertilizers, herbicides, manure, Mucuna fallow, and cowpea rotation into grain sorghum cropping systems.