Improving Agronomic Structure in Econometric Models of Climate Change Impacts

Economists are relying on agronomic concepts to construct weather or climate independent variables and improve the reliability and efficiency of econometric models of climate change impact on U.S. agriculture. The use of cumulative heat measures in agronomy (growing degree-days), has recently served as a basis for the introduction of plurimonthly calendar heat variables in these models. However, season-long weather conditions seem at odds with conventional agronomic wisdom that emphasizes crucial differences in crop stage sensitivity to environmental stress. In this paper I show that weather variables matched to key corn development stages provide an enhanced and more stable fit than their calendar counterparts. More importantly, the proposed season-disaggregated framework yields very different implications for adaptation than its calendar counterparts as it indicates that most of the projected yield damages are accounted during the flowering period, a relatively short period in the crop cycle. This should open the door to more advanced yield models that account for additional possibilities of adaptation and thus provide a more nuanced outlook on the potential impacts of climate change on crop yields.agriculture, climate change, corn, degree-days, phenology, proxy, yield, Production Economics, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy, Q54, C23,

Genetic dissection of photoperiod response based on GWAS of pre-anthesis phase duration in spring barley

Heading time is a complex trait, and natural variation in photoperiod responses is a major factor controlling time to heading, adaptation and grain yield. In barley, previous heading time studies have been mainly conducted under field conditions to measure total days to heading. We followed a novel approach and studied the natural variation of time to heading in a world-wide spring barley collection (218 accessions), comprising of 95 photoperiod-sensitive (Ppd-H1) and 123 accessions with reduced photoperiod sensitivity (ppd-H1) to long-day (LD) through dissecting pre-anthesis development into four major stages and sub-phases. The study was conducted under greenhouse (GH) conditions (LD; 16/8 h; ∼20/∼16°C day/night). Genotyping was performed using a genome-wide high density 9K single nucleotide polymorphisms (SNPs) chip which assayed 7842 SNPs. We used the barley physical map to identify candidate genes underlying genome-wide association scans (GWAS). GWAS for pre-anthesis stages/sub-phases in each photoperiod group provided great power for partitioning genetic effects on floral initiation and heading time. In addition to major genes known to regulate heading time under field conditions, several novel QTL with medium to high effects, including new QTL having major effects on developmental stages/sub-phases were found to be associated in this study. For example, highly associated SNPs tagged the physical regions around HvCO1 (barley CONSTANS1) and BFL (BARLEY FLORICAULA/LEAFY) genes. Based upon our GWAS analysis, we propose a new genetic network model for each photoperiod group, which includes several newly identified genes, such as several HvCO-like genes, belonging to different heading time pathways in barley

Effect of substrates on germination and seedling emergence of sunflower (Helianthus annuus L.) at the Yongka Western Highlands Research/Garden Park, Bamenda-Cameroon

A study was carried out at the Yongka Western Highlands Research Garden Park, Nkwen­Bamenda in Cameroon to evaluate the effect of substrates on the germination and seedling emergence of sunflower (Helianthus annuus L.). Seeds of African Giant variety were used with six substrate media (sawdust, sand, soil, sawdust­sand, sawdust­soil and sand­soil). The experiment was laid out in a Randomized Complete Block Design in three replications. Germinated seeds were counted daily for a 15 days period. To estimate seedling emergence from two Weeks After Sowing (WAS) up to four WAS, data on seedling height and number of leaves were recorded. The results showed that germination started 8 days after sowing for all substrates. Germination rate was significantly affected by the substrates but the rates were less than 80%. The highest germination rate was recorded on the soil substrate (75%) while the lowest rate (25%) was recorded on the sawdust substrate. Seedlings on the sawdust substrate were also less vigorous and had less leaves (12.67 cm height and 4.7 leaves) than those on other substrates at four WAS (50–63 cm and 12.6–15.3 leaves). Based on the results, it is recommendable to use the soil substrate to nurse African Giant seeds

Impact of the quality of organic amendments on size and composition of the weed seed bank

In addition to improving the soil quality, organic amendments of soils may affect weed seed survival, emergence, growth and reproduction. This study evaluated the effects of applications of different qualities of organic amendments on size and composition of the weed seed bank in a field under sequential cropping over 4 years. Fertilisation systems tested included farmyard manure, vegetable fruit and garden waste compost, two types of farm compost differing in carbon:nitrogen (C:N) ratio, cattle slurry and mineral fertiliser. All organically amended plots received equal amounts of C. Crop growth was equalised on all plots by applying supplemental mineral N. Seed bank sampling took place in May 2009 to a depth of 10 cm. The weed seed bank was analysed using the seedling emergence method. Despite equal crop growth in fertilised plots, total seed bank density was lowest in plots amended with compost with low C:N ratio and highest in slurry-amended plots. Observed differences in seed bank densities reflected differences in soil organic carbon content and microbial biomass. At plot level, hard-coated seeds in the seed bank (e.g. Chenopodium spp.) were inversely related to soil microbial activity. Observed differential responses of species to applied fertilisers might be attributed to interspecific differences in resistance against microbial seed degradation. Compost-based fertilisation systems could be sustainable tools for incorporation into integrated weed control strategies aiming at depleting the weed seed bank

Disease control with quality compost in pot and field trials

Quality compost can have a positive effect on soil fertility and plant growth and health. This positive effect is not only observable in the laboratory, but also by growers. Phytopathological problems could be solved with the use of compost. Durable success can only be obtained if a quality management is resolutely followed. Further research is needed to optimize the quality management of compost production and utilization. For example, very little is known about the long-term effect of the different composts on soil fertility and disease receptivity

Combining biophysical and price simulations to assess the economics of long-term crop rotations

Long-run rotational gross margins were calculated with yields derived from biophysical simulations in APSIM over a period of 100+ years and prices simulated in @Risk based on subjective triangular price distributions elicited from the Jimbour Plains farmer group. Rotations included chickpeas, cotton, lucerne, sorghum, wheat and different lengths of fallow. Output presented to the farmers included mean annual GMs and distributions of GMs with box and whisker plots found to be suitable. Mean-standard deviation and first and second-degree stochastic dominance efficiency measures were also calculated. Including lucerne in the rotations improved some sustainability indicators but reduced profitability.Crop Production/Industries, Farm Management,

An agronomic evaluation of new safflower (Carthamus tinctorius L.) germplasm for seed and oil yields under Mediterraean climate conditions

Interest in oilseed crops for agro-industrial research and development projects has increased in the Mediterranean area, in recent years. Saffloower (Carthamus tinctorius L.) is of potential interest for agriculture mainly due to fatty acid content variability in the seed oil. The aim of this study was to assess the agronomic performance of 16 new safflower accessions together with safflower variety Montola 2000, used as a reference, in a semi-arid environment. Research was carried out in Sicily (Italy) from 2013–2014. Hierarchical cluster analysis carried out on the fatty acid composition of safflower accessions resulted in their division into four main groups. Linoleic, oleic and palmitic acids were the main fatty acids present in the accessions. Seed yield was 1.11 t ha-1 on average and seed oil content was found to be approximately 35.01% of dry matter on average. Positive and significant relationships between seed/oil yield and other tested traits were found. The carbon, hydrogen and nitrogen content as a percentage of dry matter varied greatly both for the above- and belowground plant parts on average. This study confirms the interest of safflower for both food and non-food applications, offering interesting prospects in semi-arid regions

Comparing Hemp Seed Yields (Cannabis sativa L.) of an On-Farm Scientific Field Experiment to an On-Farm Agronomic Evaluation Under Organic Growing Conditions in Lower Austria

Hemp seed yields of the variety Fedora-19 in an on-farm scientific field experiment on small plots and in an on-farm evaluation in 11 hemp fields under practical organic growing conditions in Lower Austria were compared to give a realistic view of the variability of yields. Dry matter seed yields from the on-farm field experiment ranged from 127 to 143 g/m2. Under practical growing conditions, yields ranged from 34 to 151 g/m2 in the sample plots. The reported hemp seed yield after combine harvesting, drying, and cleaning was between 324 kg/ha and 717 kg/ha. The results of the experiment show that harvesting by hand considerably influences yields. Yields of the manual harvest in sample plots indicate a high correlation with yields harvested by the combine harvester (R2 = 0.91). The commercial yield is 71% of the yields recorded in sample plots in the fields. Our data questions the transfer of results and conclusions drawn from the data of scientific field experiments that employ manual harvest to that of practical circumstances, and support the notion of on-farm research

Desk study to apply knowledge developed for conventional horticulture to the control of pests in organic vegetables (OF0179)

This is the final report for Defra project OF0179. The demand for organic vegetable and salad crops is likely to increase as a result of the projected requirements of the multiple retailers. The threat of yield and quality reductions due to pest damage is a major constraint to increasing the organic vegetable crop area. The aim of this project is to demonstrate how methods of pest control developed for conventional vegetable production can be adapted for use by organic growers. The project concentrates on the pest insects that cause damage to umbelliferous and cruciferous vegetable crops. Umbelliferous crops are attacked by one major pest insect, the carrot fly (Psila rosae), and two minor pests, whereas cruciferous crops are attacked by about eight major, and over 40 less important pests. A strategy for reducing carrot fly damage in organically grown umbelliferous crops was produced. The strategy is based on the existing carrot fly forecast, on published data and on information collected previously at HRI. This includes the contribution that can be made by partial host plant resistance. Commercial breeding lines of carrots now have levels of partial resistance up to 75% and, if used in combination with late sowing, could reduce infestations by more than 90% when compared with a susceptible variety sown early. The carrot fly forecast was adapted to predict 1) the proportion of the first generation of flies that will lay eggs on crops sown on different dates and 2) the timing of emergence of the subsequent (second) fly generation within the crop. Field experiments confirmed that late sowing is an effective method of reducing carrot fly damage. The model was modified to identify the times at which crops should be covered to reduce damage by carrot fly larvae. Previous experiments have shown that to avoid damage by carrot fly larvae, crop covers should be applied to susceptible crops before the start of fly emergence. Although third generation carrot flies may be active after the end of September, their progeny do not damage overwintering crops, so late control is unnecessary. The strategy for reducing carrot fly damage in umbelliferous crops grown organically was evaluated in 2001. Participating growers grew plots of a partially resistant variety and applied/removed crop covers according to the carrot fly forecast. At harvest, the experimental plots, with one exception, suffered similar or less damage than the main area of crop, that had been grown according to standard practice. A strategy for controlling the pest insects of organically-grown cruciferous crops was developed. This is based on existing forecasts for several crucifer pests. The pest forecasts were verified in a field experiment in 2000. The literature was reviewed to 1) identify crop/pest combinations where it would be advantageous to apply covers to exclude pests, 2) find simple ways of sampling crops to detect the presence of each species, and 3) indicate the best time to apply the control measures available to organic growers. Crop covers can be used to exclude many crucifer pests. However, if aphids are able to penetrate the covers then infestations may be greater than if the crop was left uncovered. The crucifer pest control strategy was evaluated in 2001 in the organic areas at HRI Kirton and HRI Wellesbourne using forecasts for several pests and pheromone traps to monitor diamond-back moths. Plants were inspected for aphids and caterpillars. Treatments (crop covers or garlic for cabbage root fly, soft soap for aphids, Bacillus thuringiensis for caterpillars) were applied as necessary. In general, pest damage was not severe and where a large percentage of the crop was unmarketable, this was due to non-pest damage. A workshop on carrot fly control was held at HDRA, Ryton in January 2002. As a result of this project, and the conclusions drawn from this workshop, two factsheets (carrot fly and crucifer pest control in organic crops) have been produced for publication by the HDC. Other sources of information, such as the HDC/HRI pest forecasts, will be publicised through the HDRA pest and disease e-mail group. There is a more detailed summary at the start of the attached report document

Growth and competition model for organic weed control

There is a more detailed Executive Summary at the top of the attached document, which is the final report for Defra Project OF0177. The project aimed to examine the organic extension of a simple mechanistically-based growth and competition model, calibrated to data originally gained from conventional vegetable production. Essentially the model simulation follows the growth of each crop and weed plant as they compete for space and light during and after canopy closure. The growth and competition model has been modified to simulate crop and weed growth of multiple cohorts so that the onset of crop weed competition can be predicted. This onset of competition marks the point when it is essential to remove weeds (i.e. critical weeding time); otherwise, there will be a penalty to crop yield. The model can be applied to determine the onset of competition between competing species (i.e. crop and weed). In organic crops this would be the time when physical removal of the weeds (either by means of mechanical or hand weeding methods) was essential to prevent yield loss. To test the ability of the model to identify critical weeding times, model predictions were compared with historical experimental data. The inputs to the model are starting plant weights and the numbers of individuals per unit area of the crop and weed species for each cohort at each day of the simulation. Solar radiation was used to drive the model. All the growth parameters were species specific and where a number of weed species are competing with the crop in a mixed population, then a general set of parameters representing the mean of a range of parameterised weed species were used. Repeatedly running the simulation with different starting inputs from a range of historical data sets indicated that the observed critical weeding time was described well by the model. To examine the applicability of the principle of the growth model to an organic cropping situation, the predicted optimum timing of weed removal simulated by the model was incorporated as a treatment into an existing organic carrot trial. The aim was to see whether the weeding time simulated by the model achieved comparable or better results than the weeding by the unaided judgement of the grower.The results demonstrated that there was certainly no disadvantage to using the model in that year to aid in the decision making process. A small-scale trial was made in year 3, incluing cabbage plus three previously unparameterised crops; broccoli, cauliflower and leeks. The crop parameters for cabbage were used to drive the cauliflower and broccoli simulations and onion parameters for leeks. Three treatments were; weeding once as recommended by advisors at HDRA, weeding once as predicted by the model and left weedy throughout to test the competitive level of the weed flora. Inputs into the model were solar radiation, crop transplant weights and numbers, and weed weights and numbers during the early weeks of crop growth. Adjustment of the model using the final crop weights was related to the different relative growth rates of the crops in organic soils, compared with the higher N levels in conventional soils from where the parameters had been originally derived. After recalibration, the model re-confirmed the mid-August onset of competition, but tended to over predict the degree of weed competition. The notable exception was the leek crop which was more sensitive to competition than its brassica counterparts and gave a good illustration of the potential power of the model. As part of the project several presentations have been made to growers during the final year, which have allowed a dialogue and awareness to develop highlighting the practical and scientific implications of the model