Carbon sequestration and selected hydraulic characteristics under conservation agriculture and traditional tillage practices in Malawi

Conservation agriculture (CA) is increasingly promoted among smallholder farmers of sub-Saharan Africa in a quest to improve food security while sustaining the natural resource base of the agro-ecosystems where agriculture is based. The aim of this study was to investigate the effects of CA and traditional tillage on soil organic carbon (SOC) and selected hydraulic properties in two contrasting agro-ecological zones of Malawi. Six farmers hosted on-farm trials in each location, with each farmer having the following treatments: CA with continuous sole maize (CA-SM), CA with maize–legume intercrops (CA-ML), and traditional tillage with continuous sole maize (CT-SM). Soil samples were randomly collected in October 2015, from farmers’ fields located in Chipeni, Chinguluwe, Lemu, and Zidyana where CA had been implemented for 10 years (2005–2015) at six depth intervals: 0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm. Bulk density, soil water characteristics, and pore size distribution were determined using undisturbed core samples. At all sites, CA improved total SOC, carbon stocks, and the stable fraction of particulate organic carbon. Maize–legume intercropping under CA had 35%, 33%, and 73% more total SOC than CT-SM in Chipeni, Lemu, and Zidyana respectively. In Chinguluwe and Lemu, CA-ML had 0.54 and 0.50 g kg–1 respectively more stable fraction of particulate organic carbon (POMP) than CT-SM; whereas in Chipeni, CA-SM had 0.73 g kg–1 higher POMP compared with CT-SM. CA also improved soil porosity, pore size distribution, and water retention capacity by increasing the proportion of mesopores and micropores compared with CT-SM. Thus, changing management practices from CT-SM to CA has the potential to improve the soil organic matter and soil hydraulic properties across agro-ecological zones in Malawi, which is important for sustainable agriculture. Farmers should be encouraged to minimise tillage, retain residues as mulch on the soil surface, and practice crop rotation

Soil methane (CH4) fluxes in cropland with permanent pasture and riparian buffer strips with different vegetation

Background Methane (CH4) has a global warming potential (GWP) 28 times that of carbon dioxide (CO2) over a 100-year horizon. Riparian buffers strips are widely implemented for their water quality protection functions along agricultural land, but conditions prevailing within them may increase the production of radiative greenhouse gases (GHGs), including CH4. However, a few information is available regarding the dynamics of unintended emissions of soil CH4 in these commonplace features of agroecosystems and how the dynamics compare with those for agricultural land. Aims To understand the dynamics of soil CH4 fluxes from a permanent upslope pasture and contiguous riparian buffer strips with different (grass, willow, and woodland) vegetation as well controls with no buffer vegetation, an experiment was carried out using the static chamber technique on a replicated plot-scale facility. Methods Gas fluxes were measured periodically with soil and environmental variables between June 2018 and February 2019 at North Wyke, UK. Results Soils under all treatments were sinks of soil CH4 with the willow riparian buffer (–2555 ± 318.7 g CH4 ha–1) having the lowest soil CH4 flux followed by the grass riparian buffer (–2532 ± 318.7 g CH4 ha–1), woodland riparian buffer (–2318.0 ± 246.4 g CH4 ha–1), no-buffer control (–1938.0 ± 374.4 g CH4 ha–1), and last, the upslope pasture (–1328.0 ± 89.0 g CH4 ha–1), which had a higher flux. Conclusions The three vegetated riparian buffers were more substantial soil CH4 sinks, suggesting that they may help reduce soil CH4 fluxes into the atmosphere in similar agroecosystems

Soil N2O and CH4 emissions from fodder maize production with and without riparian bufer strips of difering vegetation

Purpose Nitrous oxide (N2O) and methane (CH4) are some of the most important greenhouse gases in the atmosphere of the 21st century. Vegetated riparian bufers are primarily implemented for their water quality functions in agroecosystems. Their location in agricultural landscapes allows them to intercept and process pollutants from adjacent agricultural land. They recycle organic matter, which increases soil carbon (C), intercept nitrogen (N)-rich runof from adjacent croplands, and are seasonally anoxic. Thus processes producing environmentally harmful gases including N2O and CH4 are promoted. Against this context, the study quantifed atmospheric losses between a cropland and vegetated riparian bufers that serve it.Methods Environmental variables and simultaneous N2O and CH4 emissions were measured for a 6-month period in a replicated plot-scale facility comprising maize (Zea mays L.). A static chamber was used to measure gas emissions. The cropping was served by three vegetated riparian bufers, namely: (i) grass riparian bufer; (ii) willow riparian bufer and; (iii) woodland riparian bufer, which were compared with a no-bufer control. Results The no-bufer control generated the largestcumulative N2O emissions of 18.9 kg ha−1(95% confdence interval: 0.5–63.6) whilst the maize crop upslope generated the largest cumulative CH4 emissions (5.1±0.88 kg ha−1). Soil N2O and CH4-based global warming potential (GWP) were lower in the willow (1223.5±362.0 and 134.7±74.0 kg CO2-eq. ha−1 year−1, respectively) and woodland (1771.3±800.5 and 3.4±35.9 kg CO2-eq. ha−1 year−1, respectively) riparian bufers. Conclusions Our results suggest that in maize production and where no riparian bufer vegetation is introduced for water quality purposes (no bufer control), atmospheric CH4 and N2O concerns may resul

Soil CO2 emissions in cropland with fodder maize (Zea mays L.) with and without riparian buffer strips of differing vegetation

Vegetated land areas play a significant role in determining the fate of carbon (C) in the global C cycle. Riparian buffer vegetation is primarily implemented for water quality purposes as they attenuate pollutants from immediately adjacent croplands before reaching freshwater systems. However, their prevailing conditions may sometimes promote the production and subsequent emissions of soil carbon dioxide (CO2). Despite this, the understanding of soil CO2 emissions from riparian buffer vegetation and a direct comparison with adjacent croplands they serve remain elusive. In order to quantify the extent of CO2 emissions in such an agro system, we measured CO2 emissions simultaneously with soil and environmental variables for six months in a replicated plot-scale facility comprising of maize cropping served by three vegetated riparian buffers, namely: (i) a novel grass riparian buffer; (ii) a willow riparian buffer, and; (iii) a woodland riparian buffer. These buffered treatments were compared with a no-buffer control. The woodland (322.9 ± 3.1 kg ha− 1) and grass (285 ± 2.7 kg ha− 1) riparian buffer treatments (not significant to each other) generated significantly (p = < 0.0001) the largest CO2 compared to the remainder of the treatments. Our results suggest that during maize production in general, the woodland and grass riparian buffers serving a maize crop pose a CO2 threat. The results of the current study point to the need to consider the benefits for gaseous emissions of mitigation measures conventionally implemented for improving the sustainability of water resources

Do NO, N2O, N2 and N2 fluxes differ in soils sourced from cropland and varying riparian buffer vegetation? An incubation study

Riparian buffers are expedient interventions for water quality functions in agricultural landscapes. However, the choice of vegetation and management affects soil microbial communities, which in turn affect nutrient cycling and the production and emission of gases such as nitric oxide (NO), nitrous oxide (N2O), nitrogen gas (N2) and carbon dioxide (CO2). To investigate the potential fluxes of the above-mentioned gases, soil samples were collected from a cropland and downslope grass, willow and woodland riparian buffers from a replicated plot scale experimental facility. The soils were re-packed into cores and to investigate their potential to produce the aforementioned gases via potential denitrification, a potassium nitrate (KNO3−) and glucose (labile carbon)-containing amendment, was added prior to incubation in a specialized laboratory DENItrification System (DENIS). The resulting NO, N2O, N2 and CO2 emissions were measured simultaneously, with the most NO (2.9 ± 0.31 mg NO m−2) and N2O (1413.4 ± 448.3 mg N2O m−2) generated by the grass riparian buffer and the most N2 (698.1 ± 270.3 mg N2 m−2) and CO2 (27,558.3 ± 128.9 mg CO2 m−2) produced by the willow riparian buffer. Thus, the results show that grass riparian buffer soils have a greater NO3− removal capacity, evidenced by their large potential denitrification rates, while the willow riparian buffers may be an effective riparian buffer as its soils potentially promote complete denitrification to N2, especially in areas with similar conditions to the current study

Intravitreal vs. subtenon triamcinolone acetonide for the treatment of diabetic cystoid macular edema

<p>Abstract</p> <p>Background</p> <p>To assess the efficacy of the intravitreal (IVT) injection of Triamcinolone Acetonide (TA) as compared to posterior subtenon (SBT) capsule injection for the treatment of cystoid diabetic macular edema.</p> <p>Methods</p> <p>Fourteen patients with type II diabetes mellitus and on insulin treatment, presenting diffuse cystoid macular edema were recruited. Before TA injection all focal lakes were treated by laser photocoagulation. In the same patients one eye was assigned to 4 mg IVT injection of TA and the fellow eye was then treated with 40 mg SBT injection of TA. Before and one, three and six months after treatment we measured visual acuity with ETDRS chart as well as thickness of the macula with optical coherence tomography (OCT) and intraocular pressure (IOP).</p> <p>Results</p> <p>The eyes treated with an IVT injection displayed significant improvement in visual acuity, both after one (0.491 ± 0.070; p < 0.001) and three months (0.500 ± 0.089; p < 0.001) of treatment. Significant improvement was displayed also in eyes treated with an SBT injection, again after one (0.455 ± 0.069; p < 0.001) and three months (0.427 ± 0.065; p < 0.001). The difference between an IVT injection (0.809 ± 0.083) and SBT injection (0.460 ± 0.072) becomes significant six months after the treatment (p < 0.001).</p> <p>Macular thickness of the eyes treated with IVT injection was significantly reduced both after one (222.7 ± 13.4 μm; p < 0.001) and after three months (228.1 ± 10.6 μm; p < 0.001) of treatment. The eyes treated with SBT injection displayed significant improvement after one (220.1 ± 15.1 μm; p < 0.001) and after three months (231.3 ± 10.9 μm; p < 0.001). The difference between the eyes treated with IVT injection (385.2 ± 11.3 μm) and those treated with SBT injection (235.4 ± 8.7 μm) becomes significant six months after the treatment (p < 0.001).</p> <p>Intraocular pressure of the eyes treated with IVT injection significantly increased after one month (17.7 ± 1.1 mm/Hg; p < 0.020), three (18.2 ± 1.2 mm/Hg; p < 0.003) and six month (18.1 ± 1.3 mm/Hg; p < 0.007) when compared to baseline value (16.1 ± 1.402 mm/Hg). In the SBT injection eyes we didn't display a significant increase of intraocular pressure after one (16.4 ± 1.2 mm/Hg; p < 0.450), three (16.3 ± 1.1 mm/Hg; p < 0.630) and six months (16.2 ± 1.1 mm/Hg; p < 0.720) when compared to baseline value (16.2 ± 1.3 mm/Hg).</p> <p>Conclusion</p> <p>The parabulbar subtenon approach can be considered a valid alternative to the intravitreal injection.</p> <p>Trial registration</p> <p>Current Controlled Trials <b>ISRCTN67086909</b></p