Ermson Z. Nyakatawa

Tillage, cropping systems, and nitrogen fertilizer source effects on soil carbon sequestration and fractions.

Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0- to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH(4)NO(3) and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cotton-rye/cotton-corn than in cotton-cotton-corn and greater with NH(4)NO(3) than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm after 10 yr was greater with poultry litter than with NH(4)NO(3) in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH(4)NO(3). Poultry litter also increased PCM and MBC compared with NH(4)NO(3). Cropping increased SOC, POC, and PCM compared with fallow in NT. Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO(2) levels, and improve soil and environmental quality.

Nitrogen and phosphorus transport in runoff from compost berms on a simulated military training landscape

Compost mulches have potential to significantly offset on- and off-site environmental impacts resulting from mechanical soil disturbances and training manoeuvres on military training ranges. N and P transport was investigated in runoff from compost mulch berms made from various organic waste materials in combination with each other and with soil on a simulated military training landscape in north Alabama in 2007 and 2008. Berms were constructed using composted municipal yard waste (YW), wood chips (WC), pine bark fines (PB), and soil (SL) mixed in eight different proportions. Berms made from 100% soil which had a cumulative runoff PO4-P content of 12 mg L-1 posed the greatest threat of negatively impacting the environment from inorganic P transport. Using compost mulch material with 40% soil to build berms reduced the potential for yard waste and wood chips to cause off-site negative environmental impacts from total dissolved solids, N, and P transport. Berms made from 100% pine bark fines which had cumulative runoff values of 760, 9, 22 and 5 mg L -1, respectively, of TDS, NH4-N, NO3-N, and PO 4-P had the least potential to cause negative off-site environmental impact. To prevent negative impacts of nutrient transport in runoff from berms on training landscapes, the sites need to be well buffered to hydrologically isolate them from adjoining ecosystems.

Runoff and Sediment Transport from Compost Mulch Berms on a Simulated Military Training Landscape

Soil erosion and runoff due to mechanical disturbances on military training ranges can cause problems such as land degradation and environmental pollution of downstream ecosystems. This paper discusses runoff and sediment transport from compost mulch berms on a simulated military training landscape. The berms were constructed using mixtures of municipal yard waste (YW), wood chips (WC), pine bark fines (PB), and sub-soil (SL) in eight different proportions at Hazel Green, North Alabama, in Fall 2006. Berms made from 100% soil, which had over 140 000 L ha−1 of runoff and 13.3 kg ha−1 of sediment transport over the study period, had the greatest risk of causing off-site negative environmental effects. Berms made from 100% PB and 100% WC or combinations of compost materials without soil had the lowest risk of causing environmental pollution from runoff and sediment transport. Compared to soil, compost mulches can significantly reduce negative environmental effects to downstream ecosystems when used for berm construction on military training ranges. However, measures to minimize transport of C and N in runoff sediment, such as planting grass cover crops, need to be evaluated to make the technology more environmentally sustainable.

Correlation of Soil Cone Penetrometer Resistance and Clegg Impact Test Values on Composted Mulch Berms

The use of composted mulches for land rehabilitation, erosion control, and vegetation establishment has well documented benefits. Some of the benefits of composted mulches include better water infiltration into the soil matrix, reduced soil erosion, better soil moisture retention, improved soil structure, and reduced plant stress. Composted mulch structures are being increasingly used as a best management practice for erosion control and soil loss prevention. However, little research has documented the use of composted mulches as a structural material and change in relative strength over time. This paper discusses the readings taken from three different instruments used to gauge soil strength in the field from three sets of eight compost berms. The field instruments used was a drop cone penetrometer, a soil cone penetrometer, and a Clegg impact tester. Correlations between the different field instrument readings will be discussed and their usefulness in measuring composted berm strength were analyzed.