Physical aging of starch, maltodextrin, and maltose

The physical aging of low water content, amorphous starch/water, maltodextrin/water, and maltose/water mixtures in the glassy state was examined using mechanical testing and calorimetry. Stress relaxation measurements showed that upon storage of the glassy materials there was a time-dependent increase in both flexural modulus and mechanical relaxation time. The mechanical relaxation time increased with depth of quench below the calorimetric glass transition temperature and with aging time at the quench temperature. Calorimetry of the aged materials showed an overshoot in heat capacity in the vicinity of the glass transition. The logarithm of the mechanical relaxation time showed a simple linear relationship with the size of the overshoot expressed as an enthalpy change. The calorimetric behavior could be modeled using the Tool-Narayanaswamy-Moynihan method.     

Nitrification in subalpine balsam fir soils: Tests for inhibitory factors

Previous work has shown that nitrification is negligible in floors of subalpine balsam fir forests but proceeds vigorously in the Al horizon beneath the forest floor. This paper describes a series of experiments designed to determine the causes for lack of NO^?₃ production in the forest floor. These experiments showed that denitrification was not important and that autotrophic nitrifiers were present. Increases in pH, essential nutrients and inoculum did not enhance nitrification, indicating that an inhibitor rather than a limiting factor was involved. Analysis of forest floor and Al showed that aluminum was present at concentrations greater than those found to inhibit nitrification in culture. Since the Al was actively nitrifying, it seemed unlikely that aluminum was responsible for nitrification inhibition in the forest floor. Finally, a methanol extract of polyphenols from the forest floor was added to the Al significantly reducing nitrification. These experiments suggest that the higher phenolic concentrations are responsible for inhibition of nitrification in the forest floor.     

Analysis of agroecosystem carbon pools

We present analyses of major driving variable controls on soil C in agroecosystems. Historical changes in soil C storage in agricultural soils are characterized by large losses during transition from natural grasslands and forests. A major driver in more recent times is the steadily increasing rate of net primary production of major land areas in agriculture. Simulation and analytical models are used to predict trajectories and potential soil C storage under possible scenarios of changed management and climate. Database and analytical requirements for extrapolation from regional to global scales are outlined.     

Combining ability analysis and association of yield and yield components among selected cowpea lines

The study was carried out to determine combining ability and association of yield and yield components among crosses derived from seven selected cowpea (Vigna unguiculata (L.) Walp) parents. Twenty-one hybrids were generated from diallel crosses excluding reciprocals. Hybrids along with seven parents were studied for combining ability and phenotypic correlations for seed yield and eight yield components. The result indicated that the general combining ability (gca) and specific combining ability (sca) were significant for most characters indicating the importance of both additive and non-additive genetic components. Additive gene action was important for eight characters except pod number, whereas non-additive gene action was not important for nodule number and grain yield. Parental lines IT86D-716 and IT81D-985 were found to be good general combiners for grain yield and other traits. The most promising specific combiners for yield and yield components were from crosses including IT87D-697-2 × IT86D-716, IT88D-867-11 × IT86D-716, IT93K-624 × IT87D-697-2, and IT87D-697-2 × IT92KD-405-1. Significant positive phenotypic correlations were observed between seed yield with pod length (POL), number of pods per plant (PON), and number of seeds per pod (SPD). POL, pod number per plant, SPD, and grain yield were identified as the best selection criteria that could be used in cowpea breeding programs.     

Poverty and livelihoods after full‐time farming: A South‐East Asian view

Abstract: Drawing on Harold Brookfield's seminal interventions on intensification and disintensification in tropical agriculture, the paper argues that a de‐linking of poverty and livelihoods in rural areas from farming and agricultural resources is occurring in rural South‐East Asia. This is often driven as much by changes in lifestyles and life views than by economic and environmental imperatives. The paper proposes that farming is in the process of losing its resonance and significance for the rural poor. Emerging patterns of change in the South‐East Asian countryside are used to construct a generalised framework of agrarian transition where the current trend towards pluriactivity is likely to be replaced by a mixed landscape of agrarian entrepreneurs, neopeasants and remnant smallholders. The paper concludes by reflecting on the implications of this trajectory for understanding poverty and pro‐poor interventions in the countryside.     

Managing risk and vulnerability in Asia: A (re)study from Thailand, 1982–83 and 2008

In the 1980s, rural settlements in the Northeast of Thailand were farming focused, and strategies of living were structured around the need to secure subsistence in the face of a capricious environment and a weak developmental state. More than half of households in the region lived below the poverty line, and the immediate prospects for ‘development’ were not bright. Drawing on a 25‐year longitudinal study of two villages in Mahasarakham, the paper describes and reflects on how risk and vulnerability have been re‐shaped during a quarter of a century of profound economic and social change. From largely environmental and local, the pattern of risk and opportunity have become increasingly economic and non‐local as external events wash across the shores of rural settlements like Ban Non Tae and Ban Tha Song Korn.     

Comparison of wetland and agriculture drainage as sources of biochemical oxygen demand to the San Joaquin River, California

For many years, the San Joaquin River (SJR) has had low dissolved oxygen conditions intermittently during the late summer and early fall. The low dissolved oxygen conditions are impacting critical fish habitat and the SJR is being regulated under a state of California remediation plan that includes the development of a total maximum daily load (TMDL) allocation for oxygen demanding substances. In support of the development of a scientific TMDL allocation, studies are being conducted to characterize water quality in the many tributaries of the SJR. This study identified the sources of biochemical oxygen demand (BOD) in two western tributaries of the SJR, Mud Slough and Salt Slough, and measured the loads of BOD, algae, and ammonia entering the SJR from wetland and agricultural sources.

Mud and Salt Sloughs drain the Grassland Watershed. The watershed contains seasonal wetlands, irrigated farmland, and other agricultural lands. This drainage is under close regulatory scrutiny, because it produces a majority of the selenium and boron entering the SJR. In this study, wetland and irrigated agricultural drainage were sampled separately and a comparison was made to determine differences in water quality. In addition, water entering the study area was compared to water exiting the study area to determine the effect of water use in the region on water quality.

This study demonstrated that BOD loads from the Grassland Watershed to the SJR were proportional to flow during June–October, the most critical time for dissolved oxygen deficits in the lower SJR. This indicates that Mud and Salt Sloughs are not producing more BOD than other tributaries in the region that are not under close regulatory scrutiny. The BOD concentration of wetland drainage is higher than that of agricultural drainage, but the higher agricultural drainage flows result in a higher mass loading of BOD. Wetland flooding and irrigation of crops both had a negative impact on water quality. Algal growth was identified as the major source of BOD in agricultural drainage and locations where BOD control could potentially be implemented were identified.     

Daily evapotranspiration estimates from extrapolating instantaneous airborne remote sensing ET values

In this study, six extrapolation methods have been compared for their ability to estimate daily crop evapotranspiration (ET_d) from instantaneous latent heat flux estimates derived from digital airborne multispectral remote sensing imagery. Data used in this study were collected during an experiment on corn and soybean fields, covering an area of approximately 12 × 22 km, near Ames, Iowa. ET_d estimation errors for all six methods and both crops varied from −5.7 ± 4.8% (MBE ± RMSE) to 26.0 ± 15.8%. Extrapolated ET_d values based on the evaporative fraction (EF) method better compared to eddy covariance measured ET values. This method reported an average corn ET_d estimate error of −0.3 mm day⁻¹, with a corresponding error standard deviation of 0.2 mm day⁻¹, i.e., about 5.7 ± 4.8% average under prediction when compared to average ET_d values derived from eddy covariance energy balance systems. A solar radiation-based ET extrapolation method performed relatively well with ET_d estimation error of 2.2 ± 10.1% for both crops. An alfalfa reference ET-based extrapolation fraction method (ET_rF) yielded an overall ET_d overestimation of about 4.0 ± 10.0% for both crops. It is recommended that the average daily soil heat flux not be neglected in the calculation of ET_d when utilizing method EF. These results validate the use of the airborne multispectral RS-based ET methodology for the estimation of instantaneous ET and its extrapolation to ET_d. In addition, all methods need to be further tested under a variety of vegetation surface homogeneity, crop growth stage, environmental and climatological conditions.

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