“Supply and demand trends for fertilizer in Zimbabwe: 1930 to date”: Key drivers and lessons learnt

The fertilizer sector in Zimbabwe has evolved over the years in response to different policy changes based on the government’s priorities on agricultural development. The industry grew from the 1930s that targeted primarily large scale commercial farmers, through the liberalization period of the mid 1990s, and recent changes that have introduced controls on the marketing system. Since 2000, following the fast track land reform program, Zimbabwe has faced food insecurity challenges that have been exacerbated by the political and economic crises. This prompted the government to adopt policies that have reduced private sector interests in fertilizer supply. In this situation where explicit fertilizer markets have been absent, relief programs have been leading in facilitating deliveries of fertilizers to poorer smallholder farmers located even in remote areas. The supply of fertilizers in Zimbabwe has been driven by government policy, finance and infrastructure while the demand has primarily been a function of farmer’s capacity to acquire fertilizers, availability of water and farmers knowledge of fertilizer use. There is need for a policy shift that promotes a competitive fertilizer marketing to support a broader range of farmers in Zimbabwe leading to agricultural productivity growth. Investment in infrastructure is critical to reduce marketing costs and to boost fertilizer demand; policies that strengthen farmer’s capacity to acquire fertilizers and increase their knowledge on fertilizer use complemented by technologies that promote water use efficiencies are needed.Fertilizer, supply and demand, policy reform, consumption trends, Crop Production/Industries,

Conservation Agriculture Practices and Adoption by Smallholder Farmers in Zimbabwe

This study is based on a panel survey interviewing 416 farmers practising conservation agriculture for at least five cropping seasons. Farmers obtained higher yields on conservation agriculture plots than on nonconservation agriculture ones. The mean maize yield on conservation agriculture was 1546 kg/ha compared to 970 kg/ha for non-conventional draft tillage plots across all 15 districts. However, the contribution of conservation agriculture to total household food security requirements was limited due to small plot sizes. Labor and land still remains a major challenge that limits the expansion of conservation agriculture area. Winter weeding remains a challenge, with 63% of farmers practicing it. Application of residues is still limited (56% of farmers practising it). Fertilizer application is largely dependent on access to free fertilizer. The survey results show that the 78 % of the respondent farmers were initially selected by the NGOs and were provided with inputs such as seed and fertilizer. The other 22% of the farmers in the sample were selected as spontaneous adopters, who did not initially receive any NGO support to implement conservation agriculture practices. Eleven percent of the interviewed farmers had stopped conservation agriculture practices by the 2008/09 cropping season due to withdrawal of input support by NGOs. Research should continue to explore different recommendations for different areas as farmers face dynamic agro-ecological and soil environments. Conservation agriculture should not be introduced as a blanket technology for all areas, but should be flexible and adaptable to local conditions.conservation agriculture, planting basins, yield gains, adoption labor, and fertilizer, Farm Management, Research and Development/Tech Change/Emerging Technologies, Resource /Energy Economics and Policy,

Exploring the Likelihood of Entanglements and Interactions with a PTO Knuckle

Power take-off (PTO) is a common method of transferring power from a tractor to a towed piece of machinery. The PTO is also a well-documented cause of severe and often permanent disabling injuries to farm operators. The physical conditions that cause entanglements are not well established. Several studies have explored the parameters of PTO entanglements as materials have been drawn across a rotating PTO knuckle to test for entanglement probability. The objective of this study was to determine probability of entanglement when materials are dropped vertically onto a PTO knuckle spinning at 540 RPM. A total of 360 randomized trials were conducted with 10 replications for each of the six positions (center of yoke, edge of yoke rotating downward, edge of yoke rotating upward, center of cross, edge of cross rotating downward, and edge of cross rotating upward), and six different types of materials (woven cotton athletic shoe lace, cotton work boot lace, leather boot lace, cotton twine, denim strip, and Tyvek® strip). Not a single entanglement was recorded. Dramatic high speed video imagery authenticates the material‘s motion and path as it interacts with the rotating PTO knuckle

Universal Baxterization for Z\mathbb{Z}-graded Hopf algebras

We present a method for Baxterizing solutions of the constant Yang-Baxter equation associated with $\mathbb{Z}$-graded Hopf algebras. To demonstrate the approach, we provide examples for the Taft algebras and the quantum group $U_q[sl(2)]$.Comment: 8 page

\u3cem\u3eiac\u3c/em\u3e Gene Expression in the Indole-3-Acetic Acid-Degrading Soil Bacterium \u3cem\u3eEnterobacter soli\u3c/em\u3e LF7

We show for soil bacterium Enterobacter soli LF7 that the possession of an indole-3-acetic acid catabolic (iac) gene cluster is causatively linked to the ability to utilize the plant hormone indole-3-acetic acid (IAA) as a carbon and energy source. Genome-wide transcriptional profiling by mRNA sequencing revealed that these iac genes, chromosomally arranged as iacHABICDEFG and coding for the transformation of IAA to catechol, were the most highly induced (\u3e29-fold) among the relatively few (iac cluster were genes for a major facilitator superfamily protein (mfs) and enzymes of the β-ketoadipate pathway (pcaIJD-catBCA), which channels catechol into central metabolism. This entire iacHABICDEFG-mfs-pcaIJD-catBCA gene set was constitutively expressed in an iacR deletion mutant, confirming the role of iacR, annotated as coding for a MarR-type regulator and located upstream of iacH, as a repressor of iac gene expression. In E. soli LF7 carrying the DNA region upstream of iacH fused to a promoterless gfp gene, green fluorescence accumulated in response to IAA at concentrations as low as 1.6 μM. The iacH promoter region also responded to chlorinated IAA, but not other aromatics tested, indicating a narrow substrate specificity. In an iacR deletion mutant, gfp expression from the iacH promoter region was constitutive, consistent with the predicted role of iacR as a repressor. A deletion analysis revealed putative −35/−10 promoter sequences upstream of iacH, as well as a possible binding site for the IacR repressor

Signed zeros of Gaussian vector fields-density, correlation functions and curvature

We calculate correlation functions of the (signed) density of zeros of Gaussian distributed vector fields. We are able to express correlation functions of arbitrary order through the curvature tensor of a certain abstract Riemann-Cartan or Riemannian manifold. As an application, we discuss one- and two-point functions. The zeros of a two-dimensional Gaussian vector field model the distribution of topological defects in the high-temperature phase of two-dimensional systems with orientational degrees of freedom, such as superfluid films, thin superconductors and liquid crystals.Comment: 14 pages, 1 figure, uses iopart.cls, improved presentation, to appear in J. Phys.

Dynamics of Line-Driven Winds from Disks in Cataclysmic Variables. I. Solution Topology and Wind Geometry

We analyze the dynamics of 2-D stationary, line-driven winds from accretion disks in cataclysmic variable stars. The driving force is that of line radiation pressure, in the formalism developed by Castor, Abbott & Klein for O stars. Our main assumption is that wind helical streamlines lie on straight cones. We find that the Euler equation for the disk wind has two eigenvalues, the mass loss rate and the flow tilt angle with the disk. Both are calculated self-consistently. The wind is characterized by two distinct regions, an outer wind launched beyond four white dwarf radii from the rotation axis, and an inner wind launched within this radius. The inner wind is very steep, up to 80 degrees with the disk plane, while the outer wind has a typical tilt of 60 degrees. In both cases the ray dispersion is small. We, therefore, confirm the bi-conical geometry of disk winds as suggested by observations and kinematical modeling. The wind collimation angle appears to be robust and depends only on the disk temperature stratification. The flow critical points lie high above the disk for the inner wind, but close to the disk photosphere for the outer wind. Comparison with existing kinematical and dynamical models is provided. Mass loss rates from the disk as well as wind velocity laws are discussed in a subsequent paper.Comment: 21 pages, 10 Postscript figures; available also from http://www.pa.uky.edu/~shlosman/publ.html. Astrophysical Journal, submitte

Quantum Bit Regeneration

Decoherence and loss will limit the practicality of quantum cryptography and computing unless successful error correction techniques are developed. To this end, we have discovered a new scheme for perfectly detecting and rejecting the error caused by loss (amplitude damping to a reservoir at T=0), based on using a dual-rail representation of a quantum bit. This is possible because (1) balanced loss does not perform a ``which-path'' measurement in an interferometer, and (2) balanced quantum nondemolition measurement of the ``total'' photon number can be used to detect loss-induced quantum jumps without disturbing the quantum coherence essential to the quantum bit. Our results are immediately applicable to optical quantum computers using single photonics devices.Comment: 4 pages, postscript only, figures available at http://feynman.stanford.edu/qcom