Soil organic carbon dynamics of improved fallow-maize rotation systems under conventional and no-tillage in Central Zimbabwe

Fallowing increases soil organic carbon (SOC) during the fallowing phase. However, this benefit is lost quickly during the cropping phase. The objective of this study was to evaluate SOC dynamics of an improved fallow-maize rotation under no-tillage (NT) and conventional tillage (CT) from time of fallow termination, through the next two cropping seasons. The treatments studied were improved fallows of Acacia angustissima (A. angustissima) and Sesbania sesban (S. sesban), natural fallow and continuous maize. Our hypothesis is that fallowing maintained higher SOC and lower soil bulk densities through the cropping phase when compared with continuous maize system and that NT maintained higher SOC when compared with CT. Soil organic carbon was significantly greater under fallows than under continuous maize from fallow termination to the end of the second cropping season. Soil organic carbon for the 0¿5 cm depths was 11.0, 10.0, 9.4 and 6.6 g kg¿1 for A. angustissima, S. sesban, natural fallow and continuous maize, respectively at fallow termination. After two cropping seasons SOC for the same depth was 8.0, 7.0, 6.1, 5.9 g kg¿1 under CT and 9.1, 9.0, 8.0, 6.0 g kg¿1 under NT for A. angustissima, S. sesban, natural fallow and continuous maize, respectively. Total SOC stocks were also higher under fallows when compared with continuous maize at fallow termination and after two cropping seasons. Soil bulk densities were lower under fallows when compared with continuous maize during the period of study. We concluded that fallows maintained greater SOC and NT sequestered more SOC than CT. Acacia angustissima was the better tree legume fallow for SOC sequestration when compared with S. sesban or natural fallow because it maintained higher SOC and lower bulk densities after two seasons of maize cropping

Constraints or Cooperation? Determinants of Secondary Forest Cover Under Shifting Cultivation

This study examines the drivers of land use in a shifting cultivation system with forest fallow. Forest fallow provides on-farm soil quality benefits, local hydrological regulation, and global public goods. An optimal control model demonstrates that farmers have an incentive to fallow less than is socially optimal, though market failures limiting crop production can have a countervailing effect by encouraging fallow. An econometric model estimated using data from the Brazilian Amazon suggests that fallowing does not result from internalization of local fallow services but instead is associated with poor market access and labor and liquidity constraints.forest, farms, fallow, ecosystem services, land use, spatial econometrics, Brazil, credit, International Development, Land Economics/Use,

Investment Games

Popular zero-commission stock trading apps like Robinhood innovate in user-experience design, featuring “gamification” practices—flashy graphics, leaderboards, and the like—that make it attractive, easy, and fun to trade stocks. Regulators are increasingly scrutinizing gamification and other digital engagement practices, with efforts underway at the SEC to adopt rules in broker-dealer and investment-advisor regulation. This attention reflects considerable skepticism about gamification in securities markets. At best, these practices encourage motivation and engagement, and democratize access to financial markets. But at worst, these practices encourage people to trade habitually and unreflectively, and more than they might want. This can lead to undesirable market-wide effects, like distorting the process by which markets allocate investment capital to firms and projects that will grow the real economy, as well as socially wasteful (and individually harmful) excessive trading. And given that interventions in retail investor choice have significant implications for market quality and wealth inequality, regulatory responses here are a high stakes matter for society broadly. Calls to regulate gamification highlight a tension at the core of securities markets. Securities law has largely ceded the field of market structure to the interests of sophisticated financial intermediaries in producing liquidity and price discovery. By permitting gamification practices that encourage active trading for the primary benefit of financial intermediaries, securities law subordinates its investor protection function to encourage wasteful investment in achieving eversmaller improvements in liquidity and price discovery. Regulatory intervention would be socially desirable, I argue, not just given what we know about retail trader behavior and its effects on personal finance and markets—but because it is an opportunity for securities law to recalibrate away from an all-out arms race in arbitrage. This Article takes up the problem of gamification and related digital engagement practices. It considers how gamification is the nearly inevitable consequence of the rise of retail investors who trade without superior information about a stock’s fundamental value, competition on brokerage commissions, and a fragmented market structure. Yet calls for regulatory interventions often elide important distinctions between how securities law should treat active traders who prefer risk, and those with preferences distorted by gamification. This Article explains how we got here; examines the social-welfare case for regulating gamification and related digital engagement practices; offers a typology of techniques that securities regulators can adopt in response; and assesses these interventions against existing securities law doctrine and policy. This Article also considers how the securities laws’ tenuous relationship with innovative stock-market technology shapes how retail investors engage with financial markets

ESTIMATION OF SOIL EROSION TIME PATHS: THE VALUE OF SOIL MOISTURE AND TOPSOIL DEPTH INFORMATION

Rates of soil erosion in the dryland cropping region of Saskatchewan are investigated under alternative cropping strategies. Chemical fallow is examined as an alternative to tillage fallow for moisture and soil conservation. Conclusions include: (a) flexible cropping increases net discounted returns and substantially reduced soil erosion compared to the predominant crop rotation; (b) chemical fallow is a viable alternative to tillage fallow but only when topsoil already has been eroded substantially; and (c) an increase in the discount rate is soil conserving, since it causes producers to plant more often rather than fallow.Land Economics/Use,

ECONOMICS OF WHEAT-FALLOW CROPPING SYSTEMS IN WESTERN NORTH DAKOTA

Income and risk aspects of wheat-fallow cropping systems are analyzed in western North Dakota. A wheat yield trend estimation model based on county yields (1950-77) is developed using independent variables of year, annual precipitation, acres of nonfallowed wheat and a dummy variable for fallow and nonfallow practices. The year-to-year change in wheat yields on fallowed and nonfallowed land indicates that summer fallow is becoming less desirable economically. Based on 1980 costs and yields, summer fallow maximizes returns to land at low yields, low wheat prices, and high nitrogen prices. Income variability is reduced under summer fallow.Crop Production/Industries,

Mentoring Experiences Among Navy Flag Officers: A Narrative Survey Approach

The literature has shown that mentoring can play an important role in leadership development, yet very little has been written concerning the phenomenon of mentoring within the military. This study serves to strengthen the data base concerning the role of mentoring, specifically within the leadership of the United States Navy. The sample frame for this study consisted of all U.S. Navy Admirals who were retired from active duty by 1996. A survey instrument concerning mentor relationships was mailed to 1479 retired admirals, where the nature and function of mentoring in their careers was assessed. Admiral\u27s descriptions of how mentor relationships were initiated, how long they lasted, important personality characteristics of mentors, and the salient benefits of mentoring were also evaluated. This study informs us that mentors have played a very important role in the lives of our nation\u27s most successful Naval officers. A mentor was found to provide encouragement, direction, key advancement positions and opportunities for junior officers to show their potential leadership abilities. Mentors were described as senior officers who modeled integrity, professionalism and leadership skills. The duration of the mentor relationships often lasted a lifetime, only ending in retirement or death of the mentor. Of particular importance was the mentor\u27s ability to instill the belief that the junior officer had potential and the ability to serve their country within the highest ranks. Strong support was given to more effectively facilitate the mentoring process in the U.S. Navy

A comparison between legume technologies and fallow, and their effects on maize and soil traits, in two distinct environments of the West African savannah

Legume¿maize rotation and maize nitrogen (N)-response trials were carried out simultaneously from 1998 to 2004 in two distinct agro-ecological environments of West Africa: the humid derived savannah (Ibadan) and the drier northern Guinea savannah (Zaria). In the N-response trial, maize was grown annually receiving urea N at 0, 30, 60, 90 and 120 kg N ha¿1. In Ibadan, maize production increased with N fertilization, but mean annual grain yield declined over the course of the trial. In Zaria, no response to N treatments was observed initially, and an increase in the phosphorus (P) and sulphur (S) fertilizer application rate was required to increase yield across treatments and obtain a response to N applications, stressing the importance of non-N fertilizers in the savannah. In the rotation trial, a 2-year natural fallow¿maize rotation was compared with maize rotated with different legume types: green manure, forage, dual-purpose, and grain legumes. The cultivation of some legume types resulted in a greater annual maize production relative to the fallow¿maize combination and corresponding treatments in the N-response trial, while there was no gain in maize yield with other legume types. Large differences in the residual effects from legumes and fallow were also observed between sites, indicting a need for site-specific land management recommendations. In Ibadan, cultivation of maize after the forage legume (Stylosanthes guianensis) achieved the highest yield. The natural fallow¿maize rotation had improved soil characteristics (Bray-I P, exchangeable potassium, calcium and magnesium) at the end of the trial relative to legume¿maize rotations, and natural fallow resulted in higher maize yields than the green manure legume (Pueraria phaseoloides). In Zaria, maize following dual-purpose soybean achieved the highest mean yield. At both sites, variation in aboveground N and P dynamics of the legume and fallow vegetation could only partly explain the different residual effects on maiz

Managing Sonchus arvensis using mechanical and cultural methods

Perennial sow-thistle (Sonchus arvensis L.) represents an increasing problem in Finland. Options for mechanical and cultural control of S. arvensis were studied in a field experiment on clay soil under organic production. The experiment consisted of different crop sequences: spring cereal (barley, Hordeum vulgare L., in 2001, oats, Avena sativa L., in 2002) with or without inter-row hoeing and/or stubble cultivation, bare fallow, fibre hemp (Cannabis sativa L.), and ley with mowing. In 2003 the entire field was sown to spring wheat. Crop plant and Sonchus shoot density and dry mass prior to cereal harvest and crop yield were assessed. The control effect was rated: bare fallow > ley > cereal with or without inter-row hoeing > poor growth fibre hemp. Bare fallow was an effective but costly way to reduce S. arvensis infestation. Introduction of a regularly mown green fallow or silage ley in the crop rotation is advisable. Mechanical weed control by inter-row hoeing in cereals limits S. arvensis growth. Infestation might also be reduced by stubble cultivation in autumn. When managing S. arvensis using mechanical and cultural methods, appropriate options, including a competitive crop, should be chosen for the specific field and rotation