Lanier Nalley

Reducing greenhouse gas emissions, water use and grain arsenic levels in rice systems

Agriculture is faced with the challenge of providing healthy food for a growing population at minimal environmental cost. Rice (Oryza sativa), the staple crop for the largest number of people on earth, is grown under flooded soil conditions and uses more water and has higher greenhouse gas (GHG) emissions than most crops. The objective of this study was to test the hypothesis that alternate wetting and drying (AWD--flooding the soil and then allowing to dry down before being reflooded) water management practices will maintain grain yields and concurrently reduce water use, greenhouse gas emissions and arsenic (As) levels in rice. Various treatments ranging in frequency and duration of AWD practices were evaluated at three locations over 2 years. Relative to the flooded control treatment and depending on the AWD treatment, yields were reduced by <1-13%; water-use efficiency was improved by 18-63%, global warming potential (GWP of CH4 and N2 O emissions) reduced by 45-90%, and grain As concentrations reduced by up to 64%. In general, as the severity of AWD increased by allowing the soil to dry out more between flood events, yields declined while the other benefits increased. The reduction in GWP was mostly attributed to a reduction in CH4 emissions as changes in N2 O emissions were minimal among treatments. When AWD was practiced early in the growing season followed by flooding for remainder of season, similar yields as the flooded control were obtained but reduced water use (18%), GWP (45%) and yield-scaled GWP (45%); although grain As concentrations were similar or higher. This highlights that multiple environmental benefits can be realized without sacrificing yield but there may be trade-offs to consider. Importantly, adoption of these practices will require that they are economically attractive and can be adapted to field scales.

Neglecting Rice Milling Yield and Quality Underestimates Economic Losses from High-Temperature Stress

Future increases in global surface temperature threaten those worldwide who depend on rice production for their livelihoods and food security. Past analyses of high-temperature stress on rice production have focused on paddy yield and have failed to account for the detrimental impact of high temperatures on milling quality outcomes, which ultimately determine edible (marketable) rice yield and market value. Using genotype specific rice yield and milling quality data on six common rice varieties from Arkansas, USA, combined with on-site, half-hourly and daily temperature observations, we show a nonlinear effect of high-temperature stress exposure on yield and milling quality. A 1°C increase in average growing season temperature reduces paddy yield by 6.2%, total milled rice yield by 7.1% to 8.0%, head rice yield by 9.0% to 13.8%, and total milling revenue by 8.1% to 11.0%, across genotypes. Our results indicate that failure to account for changes in milling quality leads to understatement of the impacts of high temperatures on rice production outcomes. These dramatic losses result from reduced paddy yield and increased percentages of chalky and broken kernels, which together decrease the quantity and market value of milled rice. Recently published estimates show paddy yield reductions of up to 10% across the major rice-producing regions of South and Southeast Asia due to rising temperatures. The results of our study suggest that the often-cited 10% figure underestimates the economic implications of climate change for rice producers, thus potentially threatening future food security for global rice producers and consumers.

How Greenhouse Gas Emission Policy and Industry Pressure Could Affect Producer Selection of Rice Cultivars

This study estimates how potential carbon policies targeted at reduction of greenhouse gas (GHG) emissions could affect selection of rice cultivars by conducting a life cycle assessment of GHG emissions and estimating the carbon sequestered for fourteen commonly sown rice cultivars across Arkansas. Market-oriented carbon-offset credits based on additionality likely would be insufficient to convince producers to change cultivars; nonetheless, there may be upstream pressure as food retailers strive to lower their overall carbon footprints. Given their higher yield per unit of GHG emission, hybrid rice cultivars appear to be positioned to respond to industry demand.

How Much is That Exam Grade Really Worth? An Estimation of Student Risk Aversion to Their Unknown Final College Course Grades

This study created an experimental design with which students can empirically assess their risk behavior with respect to exam grades within an expected utility framework. Specifically, the authors analyzed students’ risk preferences associated with taking exams and earning a “risky” unknown grade versus not taking exams and instead obtaining a “sure” grade. Students have grade-choice decisions in nonhypothetical situations that impact their actual exam grades. Estimates indicate that the more risk-averse a student is, the more willing he or she is to accept a lower certain grade and not take an exam than to run the risk of actually taking it. We believe that this experimental setup and its binding results make it an easy but effective way of teaching the obtuse concept of risk aversion.

Embedded Seed Technology and Greenhouse Gas Emissions Reductions: A Meta-Analysis

Agriculture’s significant global contribution to greenhouse gas (GHG) emissions has spurred consumer and retailer interest in GHG mitigation and may lead to incentive programs for producers to lessen GHG emissions. Along those lines, a producer choice is the use of embedded seed technology designed to enhance the marketable portion of yield through improved disease, weed, and pest management with the same or lower use of inputs. This article examines commonalities and differences across three recent studies on rice, sweet corn, and cotton, which addressed the impacts of embedded seed technology on yield, input use, and GHG emissions. Embedded seed technology can be any method of improving the physical or genetic characteristics of a seed. These seed enhancements can include physiological quality, vigor, and synchronicity (consistency across seedlings in time of emergence and size) through traditional breeding, hybrid breeding, or biotechnology.

Economic and Greenhouse Gas Emission Response to Pasture Species Composition, Stocking Rate, and Weaning Age by Calving Season, Farm Size, and Pasture Fertility

Since cow-calf operations are large contributors of agricultural greenhouse gas (GHG) emissions in North America, consequences of pasture species composition, weaning age, and stocking rate decisions were examined by operation size, calving season, and pasture fertility. Fixed resource use and seasonal prices affected the mix of forage and beef production. Overall, adding fertilizer to pasture was unprofitable, resulting in increased stocking rates and greater emissions. Calving season and attendant breeding failure rates influenced the relative profitability of the analyzed beef-production strategies, which in turn affected farm GHG emissions. More-efficient practices led to greater amounts of beef sold per bred cow.