Can Carbon Find a Home on the Range?

Resource /Energy Economics and Policy,

Weed Dynamics during Transition to Conservation Agriculture in Western Kenya Maize Production

Weed competition is a significant problem in maize (Zea mays, L.) production in Sub-Saharan Africa. Better understanding of weed management and costs in maize intercropped with beans (Phaseolus vulgaris, L.) during transition to conservation agricultural systems is needed. Changes in weed population and maize growth were assessed for a period of three years at Bungoma where crops are grown twice per year and at Trans-Nzoia where crops are grown once per year. Treatments included three tillage practices: minimum (MT), no-till (NT) and conventional (CT) applied to three cropping systems: continuous maize/bean intercropping (TYPICAL), maize/bean intercropping with relayed mucuna after bean harvest (RELAY) and maize, bean and mucuna planted in a strip intercropping arrangement (STRIP). Herbicides were used in NT, shallow hand hoeing and herbicides were used in MT and deep hoeing with no herbicides were used in CT. Weed and maize performance in the maize phase of each cropping system were assessed at both locations and costs of weed control were estimated at Manor House only. Weed density of grass and forb species declined significantly under MT and NT at Manor House and of grass species only at Mabanga. The greatest declines of more than 50% were observed as early as within one year of the transition to MT and NT in STRIP and TYPICAL cropping systems at Manor House. Transitioning to conservation based systems resulted in a decline of four out of five most dominant weed species. At the same time, no negative impact of MT or NT on maize growth was observed. Corresponding costs of weed management were reduced by $148.40 ha-1 in MT and$149.60 ha-1 in NT compared with CT. In conclusion, farmers can benefit from effective and less expensive weed management alternatives early in the process of transitioning to reduced tillage operations

Remote mapping of leafy spurge (Euphorbia esula, L.) in Northwestern Colorado

Leafy spurge (Euphorbia esula L.) has been introduced to the Yampa River in Northwestern Colorado for over 40 years and flood and runoff events transport leafy spurge propagules onto adjacent landscapes. The spread of leafy spurge beyond the river channels has yet to be mapped and recorded, and this research was conducted to map leafy spurge occurrence in the Yampa River Valley. Significant stakeholder mapping efforts took place in the summer of 2019–2021, leading to excellent spatial data on leafy spurge presence and absence along the main channel. In summer 2019, multispectral SPOT seven satellite imagery, stakeholder ground mapping efforts, and bright yellow-green leafy spurge bracts were used to interpret imagery, identify dense, unobscured patches of leafy spurge, and digitize them. Spectral signatures from training samples for leafy spurge and other land cover classes (generalized as “not leafy spurge”) were then used to train a Random Forest machine learning classification. In the summer of 2021, generated classification maps were compared to multispectral satellite imagery and stakeholder ground mapped leafy spurge presence. Mismatches were identified, and 271 validation locations were identified, navigated to, and evaluated for leafy spurge presence. Leafy spurge training samples were classified with 96% accuracy. Correctly classified leafy spurge locations had higher leafy spurge coverage and lower overstory canopy than missed leafy spurge locations. Leafy spurge growing beneath shrub canopy or growing as individual plants along the riverbanks were more likely to be missed. A frequency analysis for other plant species found at validation locations determined that smooth brome (Bromus inermis Leyss.), dandelion (Taraxacum officinale L.), and willow (Salix sp.) were most frequently misclassified as leafy spurge. In conclusion, multispectral satellite imagery was useful at remote detection of leafy spurge in open areas with dense leafy spurge coverage, but more work must be done for identification of sparse and diffuse leafy spurge infestations

Effects of Garden Amendments on Soil Available Lead and Plant Uptake in a Contaminated Calcareous Soil

Gardeners use organic and inorganic substances to enhance plant growth, which can inadvertently impact soil solubility and plant uptake of unknown contaminants. Consequently, human exposure can increase through gardening and consumption of produce grown in potentially contaminated soils. A greenhouse experiment was established to examine the effects of biochar, compost, and common inorganic fertilizer on soil lead (Pb) availability for radish (Raphanus sativus, L.) and lettuce (Lactuca sativa, L.) grown in a calcareous soil containing excessively high lead (Pb), along with Pb accumulation in radish tissue. Results indicate that soil amended with biochar and planted to radish saw an 18% reduction in available Pb and an 11% decrease in plant tissue content when compared to the control. Compost showed an 8% reduction in available Pb, but a 19% increase in tissue content. In contrast, soil with inorganic fertilizer planted to radish increased in both soil Pb availability by 11% and Pb tissue content by 40%. Adding water-soluble inorganic fertilizers to contaminated calcareous soils without added organic matter enhances soil Pb availability and often asymptomatic plant Pb bioaccumulation. In conclusion, gardeners are encouraged to test their soils for contamination and apply biochar in combination with compost, as this combination is recommended to improve soil health and aid in overcoming initial N deficiencies induced by biochar

Anthropogenic disturbances shift diameter distribution of woody plant species in Shorea robusta Gaertn. (Sal) mixed forests of Nepal

Assessing diameter distribution is an approach of observing regeneration strategies and impacts of anthropogenic disturbances on forest structural attributes. In this study, we evaluated the differences in diameter distributions in highly disturbed, moderately disturbed, and undisturbed forest sites of Buffer Zone Community Forests (BZCFs), viz. Janajagaran BZCF, Musharni Mai BZCF, and Radha Krishna BZCF of Central Terai, Nepal. Weibull and gamma distributions were fitted to explain changes in frequency distribution of diameter data collected. We observed a significant decrease in species richness (overall: p < 0.001) and density of smallest diameter class (0–10 cm diameter at breast height) stems (overall: p < 0.001) with increasing disturbances. Similarly, increase in median diameters (p < 0.01) and parameters of Weibull’s and gamma distributions along gradients from undisturbed to highly disturbed forest sites (except between moderately disturbed and undisturbed sites of Musharni Mai BZCF) were observed. Bowley coefficient of skewness was lower in all highly disturbed sites of BZCFs showing reduction in right skewness of the distribution curves with disturbances. These results indicate anthropogenic disturbances shift diameter structure of forests stands, negatively affecting abundance of small diameter–sized woody species and shifting Shorea robusta mixed forests towards even-aged stands. Keywords: Anthropogenic disturbances, Diameter distribution, Shorea robusta mixed forests, Weibull and gamma distribution

Soil Carbon and Nitrogen Mineralization and Crop Parameters in Typical Maize-Bean Intercropping in Western Kenya

Smallholder farmers in western Kenya who plant maize (Zea mays L.) intercropped with beans (Phaseolus vulgaris L.) face many challenges associated with nutrient-poor soils and weather-related crop failures. In regions where temperatures are favorable, crops are grown twice per year during long and short rainy seasons and in other regions, once per year during one long growing season. Growing crops two times per year necessitates frequent land preparation using inversion-type tillage. Little is known about the impact of current tillage-intensive crop management on annual soil organic matter (SOM) recovery. The aim of this study was to assess changes to soil carbon (C), nitrogen (N) and crop performance in typical maize-bean production during long rainy season (LR), short rainy season (SR) and a fallow period (FP) in areas where crops are grown one time (Trans-Nzoia) and two times per year (Bungoma). The two locations were sampled three times per year for a period of three years. Soils were analyzed for potentially mineralizable nitrogen (PMN), ammonium (NH4), nitrate (NO3), water filled pore space (WFPS), nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2). Results demonstrated significantly greater PMN, NH4 N2O and CO2 during SR in Bungoma compared with LR and FP suggesting high C and N mineralization caused by warmer temperatures and high frequency of tillage. Soils in Trans-Nzoia also showed elevated NH4, NO3 and N2O during the same period but the magnitude of these changes was much lower compared with Bungoma. Mineralization negatively impacted annual SOM renewal and crop production as further demonstrated by low soil total C and N and cumulative crop yields in Bungoma. Planting edible cover crops, reducing tillage and using manure should become a necessity to support sustainable crop production. Particular attention should concentrate on designing appropriate management strategies for SR season in Bungoma

Weed Dynamics during Transition to Conservation Agriculture in Western Kenya Maize Production.

Weed competition is a significant problem in maize (Zea mays, L.) production in Sub-Saharan Africa. Better understanding of weed management and costs in maize intercropped with beans (Phaseolus vulgaris, L.) during transition to conservation agricultural systems is needed. Changes in weed population and maize growth were assessed for a period of three years at Bungoma where crops are grown twice per year and at Trans-Nzoia where crops are grown once per year. Treatments included three tillage practices: minimum (MT), no-till (NT) and conventional (CT) applied to three cropping systems: continuous maize/bean intercropping (TYPICAL), maize/bean intercropping with relayed mucuna after bean harvest (RELAY) and maize, bean and mucuna planted in a strip intercropping arrangement (STRIP). Herbicides were used in NT, shallow hand hoeing and herbicides were used in MT and deep hoeing with no herbicides were used in CT. Weed and maize performance in the maize phase of each cropping system were assessed at both locations and costs of weed control were estimated at Manor House only. Weed density of grass and forb species declined significantly under MT and NT at Manor House and of grass species only at Mabanga. The greatest declines of more than 50% were observed as early as within one year of the transition to MT and NT in STRIP and TYPICAL cropping systems at Manor House. Transitioning to conservation based systems resulted in a decline of four out of five most dominant weed species. At the same time, no negative impact of MT or NT on maize growth was observed. Corresponding costs of weed management were reduced by $148.40 ha(-1) in MT and$149.60 ha(-1) in NT compared with CT. In conclusion, farmers can benefit from effective and less expensive weed management alternatives early in the process of transitioning to reduced tillage operations

Soil Microbial Substrate Properties and Microbial Community Responses under Irrigated Organic and Reduced-Tillage Crop and Forage Production Systems

<div><p>Changes in soil microbiotic properties such as microbial biomass and community structure in response to alternative management systems are driven by microbial substrate quality and substrate utilization. We evaluated irrigated crop and forage production in two separate four-year experiments for differences in microbial substrate quality, microbial biomass and community structure, and microbial substrate utilization under conventional, organic, and reduced-tillage management systems. The six different management systems were imposed on fields previously under long-term, intensively tilled maize production. Soils under crop and forage production responded to conversion from monocropping to crop rotation, as well as to the three different management systems, but in different ways. Under crop production, four years of organic management resulted in the highest soil organic C (SOC) and microbial biomass concentrations, while under forage production, reduced-tillage management most effectively increased SOC and microbial biomass. There were significant increases in relative abundance of bacteria, fungi, and protozoa, with two- to 36-fold increases in biomarker phospholipid fatty acids (PLFAs). Under crop production, dissolved organic C (DOC) content was higher under organic management than under reduced-tillage and conventional management. Perennial legume crops and organic soil amendments in the organic crop rotation system apparently favored greater soil microbial substrate availability, as well as more microbial biomass compared with other management systems that had fewer legume crops in rotation and synthetic fertilizer applications. Among the forage production management systems with equivalent crop rotations, reduced-tillage management had higher microbial substrate availability and greater microbial biomass than other management systems. Combined crop rotation, tillage management, soil amendments, and legume crops in rotations considerably influenced soil microbiotic properties. More research will expand our understanding of combined effects of these alternatives on feedbacks between soil microbiotic properties and SOC accrual.</p></div

Gypsum and Coal-bed Methane Water Modify Growth Media Properties, Nutrient Uptake, and Essential Oil Profile of Lemongrass and Palmarosa

Coal-bed methane (CBM), an important energy source, coproduces a vast amount of saline-sodic wastewater, CBM water (CBMW), with environmental and economic disposal issues. This research evaluated under a greenhouse production system the influence of gypsum (CaSO4&middot;2H2O) and CBMW on yields, essential oil (EO) content and composition in lemongrass (Cymbopogon flexuosus) and palmarosa (C. martinii), and on growth medium pH and available nutrients. CBMW treatments had higher pH than tap water treatment. Gypsum reduced pH in all CBMW treatments but did not affect pH in tap water treatment. While CBMW may increase the available Cu and Fe in growth medium, the application of gypsum may negate this effect. CBMW significantly increased growth medium Na. Gypsum increased growth medium S, and CBMW increased S in the high gypsum treatments. Palmarosa height, fresh weight, geranyl acetate, and isoneral in lemongrass EO were reduced, while geraniol in palmarosa EO increased with CBMW relative to tap water. In distillation waste plant tissue, CBMW increased Na in lemongrass and palmarosa by almost eight times; increased total P, S, and Mn in palmarosa; and reduced total N, S, Ca, and Mg in lemongrass and Ca in palmarosa, relative to tap water. This study demonstrated that CBMW may be used for greenhouse production of high-value crops, but it may affect the yields and oil content of some crops and growth medium characteristics