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11. [Article] Impacts of crop level and vine vigor on vine balance and fruit composition in Oregon Pinot noir
Vineyard management strategies, including vineyard floor management and crop level management, can be used to influence vine vigor and fruit composition. Two studies were conducted to evaluate the impact ...Citation Citation
- Title:
- Impacts of crop level and vine vigor on vine balance and fruit composition in Oregon Pinot noir
- Author:
- Vance, Amanda J.
Vineyard management strategies, including vineyard floor management and crop level management, can be used to influence vine vigor and fruit composition. Two studies were conducted to evaluate the impact of these practices on Pinot Noir in Oregon's Willamette Valley. Managing crop levels is common in cool climate vineyard production though it is a costly practice. With economic pressures, the premium winegrape industry is questioning whether they can reduce production costs and increase yields without compromising quality. A crop thinning trial was conducted in 2010 and 2011 to address these concerns and to better understand the role of vine balance on fruit composition. Crop levels were moderately (35% crop removed) or severely (65% crop removed) thinned at pre-bloom, fruit set, lag phase, or véraison and compared to full crop treatments. In both years, crop thinning reduced yields but had no effect on berry weight or cluster size. In 2010, poor fruit set reduced overall yields, and thinning treatments resulted in very few differences in vine growth, cluster architecture or fruit composition, including total soluble solids (TSS), pH, titratable acidity (TA), yeast assimilable nitrogen (YAN), anthocyanins, phenolics and tannins. In 2011, yields were much higher due to high fruit set and larger cluster size. No differences were found in vine growth (leaf areas or pruning weights) or fruit YAN, but thinned vines had higher TSS and pH and lower TA than full crop vines at harvest. Fruit thinned at lag phase and véraison had higher TSS and lower TA than fruit thinned pre-bloom. Intensity of thinning had a stronger influence on anthocyanin and tannin concentration than timing, while phenolics were not impacted by either factor. Ravaz index values (fruit yield/pruning weight) below 2.25 and leaf area to yield ratios of 2.25 to 3.25 m²/kg improved fruit composition in 2011 as did later season thinning, though data from the remaining years of this study will provide more insight into appropriate crop load metrics for cool climate Pinot Noir. A second study was implemented in 2011 to determine the impact of crop thinning in vines with different levels of vegetative vigor caused by three vineyard floor management techniques: permanent grass (Festuca rubra spp. rubra) cover (grass), alternating grass cover and tillage (grass & tilled), and tillage of every alleyway (tilled). Crop was thinned at the BB stage of berry development (EL stage 73) to one cluster per shoot (half crop) or not thinned (full crop); all cluster wings were removed at the time of thinning. Tillage treatments had been in place four years prior to the start of the study and competition for nitrogen in grass caused reduced early season vine growth, leaf chlorophyll and canopy size at both bloom and véraison while crop thinning increased canopy size at véraison. Yields were altered by tillage and crop thinning treatments, as grass had fewer clusters per shoot and berries per cluster, and crop thinning reduced yields to 64.7% of full crop across all tillage treatments. At harvest, grass had the lowest TA while TSS and pH were not affected by tillage. Crop thinning increased TSS but did not impact pH or TA. Anthocyanins were affected by both tillage and thinning and were found to be related to vine yield, YAN, leaf N, and leaf area index. Tannins were highest in grass but were not affected by crop thinning, and phenolics were not changed by either factor. Few interactions between tillage and crop thinning were found, but as variables such as yield per vine were impacted by both treatment factors, monitoring long term effects of crop
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Root rot of sweet corn in western Oregon and Washington is a significant disease that can reduce yield of intolerant cultivars of processed sweet corn by fifty percent. Root rot is caused by a complex ...
Citation Citation
- Title:
- Cover crop effects on root rot of sweet corn and soil properties
- Author:
- Miyazoe, Mikio
Root rot of sweet corn in western Oregon and Washington is a significant disease that can reduce yield of intolerant cultivars of processed sweet corn by fifty percent. Root rot is caused by a complex of soilborne organisms, including Drechslera sp., Phoma terrestris, and Pythium arrhenomanes. Processors have adopted tolerant cultivars but farmers continue to seek cultural management strategies that reduce inoculum potential. High rate manure and compost amendments (16.8 - 56.0 Mg ha⁻¹) suppress root rot of corn through general suppression but this practice is not agronomically viable. General suppression is typically associated with high rates of organic amendment and high microbial (FDA) activity. Processed vegetable farmers currently grow winter cover crops to improve soil and water quality and are interested in identifying cover crops that suppress root rot of corn and increase yield. High biomass cover crops can yield up to 12 Mg ha⁻¹ dry matter; this rate of organic amendment may or may not be sufficient to generate general suppression. However, specific cover crops, such as species and cultivars of crucifers and oats, have been shown to more suppressive than other cover crop species and cultivars against specific soilborne diseases. Oat is grown as a winter cover crop in the Willamette Valley and contains avenecin, a chemical that has been shown to have activity against pathogen propagules. In addition, in previous work in containers oat cover crops suppressed root rot of sweet corn. However, there is a concern that oat cover crops immobilize N and reduce corn yield. The objectives of this research were to 1) identify high biomass cover crops with agronomic potential for western Oregon processed vegetable cropping systems, 2) evaluate the impact of high biomass cover crops on root rot severity and yield of sweet corn, 3) determine whether there is a correlation between dry matter, soil microbial activity and root rot severity and 4) determine whether cover crops immobilize nitrogen and reduce corn yield. Research station field trials were conducted in 2003-04, 2004-05 and 2005-06 at the Oregon State University vegetable research farm in Corvallis, Oregon and an on-farm experiment was conducted in 2004-05 at Kenagy Family Farm in Albany, Oregon. Oat 'Saia' winter-killed in 2005-06 and mustard mix 'Caliente' winter-killed every winter except 2004-05, when winter temperatures never dropped below -7 °C. Rape 'Dwarf Essex', mustard 'Braco', and arugula are reliably winter-hardy. All mustard cover crop species are susceptible to white mold caused by Sclerotinia sclerotiorum, causal agent of white mold of snap bean. Oat (Avena sativa) is susceptible to barley yellow dwarf virus (BYDV), an important pathogen of grass seed crops. Mustard cover crops could contaminate cruciferous seed crops. All of the cover crop species evaluated demonstrated some potential to suppress root rot of corn. Oat 'Saia' was the most consistently suppressive; it suppressed root rot in 4 of 6 experiments. Sudangrass was suppressive in the only year it was evaluated as well as in container experiments in previous work. In general, cover crops increased or had no impact on shoot and root dry matter in greenhouse bioassays. There was only one significant cover crop treatment effect on yield; in 2006, the oat treatment increased yield by 11.6% compared to the fallow. Overall, cover crop aboveground dry matter (DM) ranged from 4.2 Mg ha⁻¹ (summer R 2003) to 12.2 Mg ha⁻¹ (winter O 2004). Overall, there was a significant relationship between cover crop DM and radicle rot severity in greenhouse bioassay but not in field experiment. Cover crop treatments consistently increased soil microbial activity. Overall, there was a significant negative correlation between microbial activity and root rot severity in greenhouse bioassays early after cover crop incorporation, but the correlation weakened over time and ultimately was lost by about 80 days after incorporation. The C:N of oat and rape residues was 51 and 21, respectively. Soil nitrogen was immobilized by both the oat and rape cover crops, but oat immobilized more N than rape. Corn grown in the oat treatment soils had lower SPAD values, but it is not clear whether foliar N was sufficiently low to reduce yield potential. There was no consistent trend in above- or below-ground corn dry matter after oat incorporation over the three years. In 2006, the oat treatment had no significant effect on corn DM but increased yield by 11.1%. More work is required to better understand the impact of oat cover crop N immobilization on corn N status and yield. Oat 'Saia' has the potential to suppress root rot of sweet corn and maintain or increase corn productivity. However, this oat cultivar is not reliably winter-hardy and is susceptible to BYDV. Future research should screen Avena species and/or cultivars for improved winter hardiness, BYDV resistance, and root rot suppressive potential.
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13. [Article] Irrigation choices for major West Coast crops : water scarcity and climatic determinants
Recent climate change forecasts have aroused growing interest in the influence of water scarcity and climate on agricultural production and irrigation practice. However, it is common in the economic literature ...Citation Citation
- Title:
- Irrigation choices for major West Coast crops : water scarcity and climatic determinants
- Author:
- Olen, Beau
Recent climate change forecasts have aroused growing interest in the influence of water scarcity and climate on agricultural production and irrigation practice. However, it is common in the economic literature to aggregate disparate crops when modeling irrigation choices. That approach confounds the crop-specific effects of climate and water scarcity that govern such choices. Given the sensitivity of agricultural production to water scarcity and climate, understanding their influence on irrigation choices is a key contribution to policy evaluation. This paper addresses the impact of water scarcity and climate on irrigation choices through estimated models of cropland proportion irrigated (PI), and crop-specific irrigation technology choice (TC) and water application rates (AR). This approach is applied to agricultural production data for major crops (orchard/vineyard, vegetable, wheat, alfalfa, hay, and pasture) on the West Coast (California, Oregon, and Washington). Crop-specific modeling provides information about the distributional impacts of agricultural policy and climate change. This advantage is particularly important for the diverse agricultural landscape of the West Coast, where the distributional impacts of policy can be complex. The most important policy implications that are found involve asset heterogeneity and the distributional impacts of agricultural policy. Several findings provide valuable information about how irrigators would respond and adapt to climate change. The current findings also lead to commonly advocated revisions to federal water subsidy policies. Some key differences between the irrigation choices of higher- and lower-value crops are also identified. Identifying these differences sheds further light on the distributional consequences of agricultural policy. Many findings from this research are crop-specific and will have a high degree of policy relevance to irrigation districts or other agricultural jurisdictions that cultivate some of the West Coast's major crops. Furthermore, the data used in this research has a large degree of variation in water scarcity and climate, making the findings applicable to other Mediterranean climates in the world. It is found that specific crops have a proclivity for certain irrigation technologies that can mitigate particular climatic stressors (i.e., frost damage and heat stress). For example, the results indicate that water pricing policies will tend not to encourage water conservation by technology adoption for many orchards, vineyards, and vegetable farms, thereby imposing pure costs to these producers. In essence, climate heterogeneity limits options available to farmers and reduces the set of production technologies that a farm can use. This finding exemplifies that with climate heterogeneity, the distribution of water policy impacts depends on prior land allocation decisions such as crop choices. Heterogeneity in land quality is also found to have important influences on TC. The effects of temperature on irrigation choices are found to be more profound than the effects of precipitation. Because of the large study region used, the effects of temperature and precipitation on irrigation choices are often found to be quadratic-like. These quadratic-like relationships reveal thresholds where irrigators begin to respond very differently to climate. However, this was not the case for all crops. Thus, it is demonstrated that the effects of climate on irrigation choices are crop-dependent. The results indicate that for several crops, the discontinuance of irrigation water (i.e., water supply or price uncertainty) creates an option value that delays and discourages adoption of water-saving technologies. The discontinuance of irrigation water is also shown to reduce water demand at the farm-level extensive proportion (i.e., PI) and crop-level intensive margin (i.e., AR). Water price is found to impact all three irrigation choices as well. Well depth is found to facilitate adoption of water-saving technologies for several crops. This paper demonstrates that irrigation choices are highly dependent on water scarcity and climate. Institutional arrangements, geographic qualities of the farm, and demographic characteristics of the farmer also exhibit important influences on irrigation choices. By using crop-specific equations, quadratic climate variables, and a study region with large variation in climate conditions, this research resolves many inconsistent findings regarding the determinants of irrigation choices. Furthermore, this study establishes a research agenda for crop-specific analysis of irrigation choices. Some of the estimated results warrant verification with further studies. Future crop-specific irrigation choice studies would benefit from panel micro data with improved land quality variables, and seasonal or monthly climate variables that are better able to identify the effects of climate stress (e.g., heat stress and frost damage) on irrigation choices.
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14. [Article] The effect of precipitation variation and fertilization level on the nutritive value of wheat residue
Five simulated precipitation patterns characteristic of the Columbia Basin and Plateau region and six fertilization rates were evaluated for their effect on percent crude protein, percent in vitro dry ...Citation Citation
- Title:
- The effect of precipitation variation and fertilization level on the nutritive value of wheat residue
- Author:
- Carey, Anne C.
Five simulated precipitation patterns characteristic of the Columbia Basin and Plateau region and six fertilization rates were evaluated for their effect on percent crude protein, percent in vitro dry matter digestibility, fiber content, and yield of wheat aftermath on a commercial farm in north central Oregon. The higher moisture regimes showed the greatest increase in percent crude protein with increasing nitrogen fertilizer levels. Chaff and straw values were significantly higher for the dry fallow-normal crop precipitation pattern than for normal fallow-dry crop pattern and significantly higher for the wet fallow-normal crop pattern than for normal fallow-wet crop. Percent in vitro dry matter digestibility also increased under the high moisture precipitation patterns and there was a positive relationship between fertilization level and digestibility. The digestibility values for chaff and straw were higher for the dry fallow-normal crop precipitation regime over the normal fallow-dry crop only at the higher fertilization levels. Examination of wet fallow-normal crop vs. normal fallow-wet crop showed increased digestibility for the pattern receiving more moisture in the fallow period, also at only the higher fertilization levels. This study indicated that higher moisture regimes resulted in increased straw and chaff yields. Although not significant for every precipitation pattern, there was indication of a positive relationship between fertilization level and straw and chaff yields. For both straw and chaff yield, no difference was seen when comparing dry fallow-normal crop and normal fallow-dry crop regimes. Testing wet fallow-normal crop vs. normal fallow-wet crop patterns revealed increased chaff yields at higher fertilization levels under the pattern receiving less moisture in the fallow period, but increased straw yields at higher fertilization levels under the pattern receiving more moisture in the fallow period. Percentages of acid detergent fiber, lignin, and cellulose were not significantly affected by precipitation variation or level of fertilization. The fertilization by precipitation pattern interaction was not a significant source of variation, with the exception of percentage crude protein of wheat straw in the first year.
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15. [Article] Weed control in nursery field production
Published November 2005. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalogCitation -
16. [Article] An ecosystem service approach to inform reactive nitrogen management in the lower Yakima River Basin, Washington
Spatially explicit ecosystem service valuation (ESV) allows for the identification of the location and magnitude of services provided by natural ecosystems to human activities along with a measure of their ...Citation Citation
- Title:
- An ecosystem service approach to inform reactive nitrogen management in the lower Yakima River Basin, Washington
- Author:
- Crowell, Morgan
Spatially explicit ecosystem service valuation (ESV) allows for the identification of the location and magnitude of services provided by natural ecosystems to human activities along with a measure of their significance based upon economic valuation. While ESV has been used to provide new insight into land use management, few studies have identified the connections between the values of ecosystem services and ecological sensitivity to nitrogen loading despite a growing body of ecosystem service literature. This research combines a GIS-based, value transfer approach to map ecosystem services in the Lower Yakima River Basin (LYRB), Washington, USA, along with estimates of nitrogen loading to identify how nitrogen management may affect ecosystem services in the basin. This analysis combines values of ecosystem services with estimates of nitrogen loading and identifies subwatersheds and specific parcels within a Groundwater Management Area (GWMA) most susceptible to reductions in ecosystem services due to excess nitrogen loading. Based on the benefit transfer analysis, wetlands and forested areas have disproportionately high values of ecosystem services when compared to their land area in the LYRB, while pasture and cultivated crops contribute much less to the total value of ecosystem service flows in proportion to the total area in the LYRB. Across the study area estimated nitrogen loads are strongly driven by the location of concentrated animal feeding operations (CAFOs) and cultivated crops. Areas of particularly high nitrogen loading and high ESV may highlight specific areas for achieving immediate success in increasing or maintaining ecosystem services through appropriately focused regulatory mechanisms. The land cover analysis however, completely neglects the values and importance of subsurface processes and groundwater resources in ecosystem service assessment, and therefore an econometric model is applied to estimate willingness to pay (WTP) to maintain safe nitrate levels in private wells. Through the incorporation of WTP estimates for groundwater quality, a more complete economic and ecological perspective on the effects of landscape N loading in the study site is highlighted. The results of these estimates clearly indicate that ecosystem services from groundwater should be considered to have significant value in the LYRB. Further economic valuation data on specific land cover types and the value of groundwater quality, whether from primary studies or meta-analysis, is needed to refine relative measures of ecosystem service values and more confidently describe these values in specific dollar amounts. Additionally, limits in spatial data resolution may contribute to errors in location and magnitude of ecosystem services, and is an area in need of further development. Despite these potential limitations, this analysis highlights a promising direction for combining spatially explicit ecosystem service valuation with nutrient loading data to identify the location and potential magnitude of effects on ecosystem services from management practices.
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In conventional cropping systems in the Willamette Valley, slow establishing grass species, such as Kentucky bluegrass (Poapratensis L.) are planted in the spring and seed is not harvested until the following ...
Citation Citation
- Title:
- Establishment of grass seed crops with cereal companion crops
- Author:
- DeHaas, Jeroen A. M.
In conventional cropping systems in the Willamette Valley, slow establishing grass species, such as Kentucky bluegrass (Poapratensis L.) are planted in the spring and seed is not harvested until the following year. Due to increasing annual production costs, it is necessary to generate a cash return from each field each production year. This can be achieved by establishing the grass seed crop with a cereal companion crop either in fall or spring. The objective of this study was to identify the suitability of establishing grass seed crops with cereal companion crops in the Willamette Valley. To realize this objective, combinations of companion crop species, seeding rates, planting arrangements and grass species were examined for suitability in a companion cropping system. In addition, competitive effects of the companion crop on undersown grasses were studied. Three field experiments were conducted at two locations in the Willamette Valley over a two-year period (1980-1982). Percent light transmittance was measured in companion crop canopies developed under different seeding rates (67.2 and 100.8 kg/ha) and planting arrangements (parallel with and across grass rows) and in different types of companion crops (winter wheat, spring wheat and spring barley). Soil water potential was determined to investigate moisture patterns due to crop competition. Tiller samples were taken from undersown grasses and from these samples the following growth parameters were determined: tiller number, tiller height, leaf weight and leaf area per tiller, Specific Leaf Weight (SLW), and Leaf Area Index (LAI). Companion crop and grass seed yields were determined to obtain information for the economic feasibility of the companion cropping system. Parallel planting of the grass and companion crops gave higher light transmittance values than cross planting. However, no beneficial effects on grass crop growth parameters were detected. Companion crop seeding rates did not result in different percent light transmittance values, or was there an effect on growth parameters of undersown Kentucky bluegrass and orchardgrass (Dactylis glomerata L.). Soil water potential was higher in Kentucky bluegrass plots established with a companion crop at Gervais than in plots established without a companion crop. Tiller number for Kentucky bluegrass was suppressed by the companion crop for the experiment in Gervais. Tiller number and LAI for Kentucky bluegrass and orchardgrass was lower when established with a companion crop in the fall of 1981 at Hyslop Farm. Tiller height, leaf weight and leaf area per tiller of Kentucky bluegrass was higher when established with a wheat companion crop at Gervais. Leaf weight per tiller and SLW of orchardgrass were suppressed by the wheat companion crop at Hyslop Farm. Differential effects on growth parameters due to different companion crops were not detected. Low companion crop yields did not offset a lower subsequent Bristol Kentucky bluegrass seed yield in Gervais. This resulted in a lower mean annual gross return for the bluegrass seed crop when established with a companion crop. Wheat companion crop yields were approximately 10,000 kg/ha and 6,300 kg/ha when planted with Kentucky bluegrass and orchardgrass, respectively, at Hyslop Farm. Grass seed yields were not obtained for this study due to time constraints. Further investigation is needed to study the effect of companion crop planting arrangements on undersown grasses. The necessity of irrigation and nitrogen fertilization immediately after companion crop harvest for companion cropping systems in the Willamette Valley also need to be further investigated.
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18. [Article] Evaluation of four quality factors in a selected winter x spring wheat cross (Triticum aestivum Vill., Host)
The nature of the genetic variation associated with a cross involving winter and spring wheat parents for four quality factors was evaluated. Yamhill, a soft white winter wheat, and Inia 66, a hard red ...Citation Citation
- Title:
- Evaluation of four quality factors in a selected winter x spring wheat cross (Triticum aestivum Vill., Host)
- Author:
- Schumaker, Karen Sue
The nature of the genetic variation associated with a cross involving winter and spring wheat parents for four quality factors was evaluated. Yamhill, a soft white winter wheat, and Inia 66, a hard red spring wheat, were selected as parents for this study. They represented distinctly different phenotypes for the attributes measured. Parents, F₁, F₂ and reciprocal backcrosses were examined for protein and lysine content, kernel hardness, and sedimentation value. Significant differences were observed between the two parents for protein content. The F₁ mean was lower than the low protein parent with the F₂ mean intermediate between the two parents. This latter factor plus a high narrow sense heritability estimate suggest that the genetic variation associated with protein content was largely due to genes which act in an additive manner. Backcrosses to either parent shifted the population toward the mean of the recurrent parent. Transgressive segregation was observed in the F₂ for both low and high protein content suggesting that selection for this trait should be effective in early generations. Parents differed significantly for lysine content with the winter parent, Yamhill displaying lysine values approaching the highest previously reported for wheat. Intermediate F₁ and F₂ population means and a high narrow sense heritability estimate suggest the genes involved function in an additive manner. The backcross progeny to Yamhill had a mean value approaching that of the recurrent parent. No transgressive segregation was observed in the F₂ for lysine content higher than Yamhill. It appears that lysine content in this cross is qualitatively inherited and that selection for improved lysine content above Yamhill appears limited. The genetic variation associated with kernel hardness appears to be largely additive with F₁ and F₂ means intermediate between the two parents and a high narrow sense heritability estimate. Transgressive segregation was observed in the F₂ generation for both soft and hard kernel types. Selection for this trait should be effective in early generations. Significant differences were observed for the parental types for sedimentation value. The F₁ and F₂ means were below the midparent value. No transgressive segregation was observed in the F₂ for either low or high sedimentation value. One backcross to the low sedimentation parent brought the population back to the low parent mean. One backcross to the high sedimentation parent shifted the population toward the recurrent parent but no individuals were recovered that approached the high parent. From this study it appears that selection for high sedimentation value types would be very difficult. Evidence provided in this study supports the concept that winter x spring crosses can provide useable genetic variation for desirable quality factors.
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19. [Article] Enhancement of the weed competitive ability of lowland rice (Oryza sativa L.) cultivars
Most of the presently grown cultivars of rice (Oryza sativa L.) have poor competitive ability against weeds if compared with traditional cultivars. Therefore, effective weed control is an important but ...Citation Citation
- Title:
- Enhancement of the weed competitive ability of lowland rice (Oryza sativa L.) cultivars
- Author:
- Ranasinghe, Lakshman L.
Most of the presently grown cultivars of rice (Oryza sativa L.) have poor competitive ability against weeds if compared with traditional cultivars. Therefore, effective weed control is an important but often costly and difficult management practice in rice crop production. If weed competitive ability of rice cultivars could be improved by changing the plant morphology and some agronomic practices, crop losses and the cost of weed control in rice production would be reduced. Three field experiments were conducted to identify weed competitive morphological traits of rice and to evaluate the effect of delaying starter fertilizer application on weed competition in rice. The nature of rice-barnyardgrass competition varies greatly with rice cultivar morphology. In an addition series experiment, the semi-dwarf, erect leaved, high yielding cultivar BG 350, which possesses much of the plant characteristics required for a high yield was affected much more than the cultivar BG 94-2, which has a tall stature, high leaf area index and good seedling vigor. In the varietal testing experiment, as predicted by the sensitivity analysis, cultivars with rapid height growth, high leaf area growth and plant dry weight increase during seedling stage, height and leaf area at maturity were associated with high competitive ability. The weed competitive ability of tested cultivars varied from relatively high in cultivars PPL and BG 94-2, moderate in BW 267-3 to poor in BG 1611 and BG 350. The delay of starter fertilizer application by 14 days in cultivar BG 350 improved its competitive ability against barnyardgrass (BYG). Under BYG competition, a 14-day delay of starter fertilizer application reduced the percent crop loss by weed competition 6.64 and 22.99% under the normal planting density in the Maha and Yala cultivation seasons, respectively. The crop-weed competition model INTERCOM simulated yield losses for the tested cultivars followed the trends observed in field experiments. However the simulated values were always higher than the observed values.
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The North Atlantic zone of Costa Rica is an alluvial plain, whose fairly good soils and warm, extremely wet climate generate serious weed problems in cultivated crops and pastureland. Basic foods - corn, ...
Citation Citation
- Title:
- The agronomic, economic and social effects of the availability of new weed control treatments to small corn farmers in the North Atlantic Zone of Costa Rica
- Author:
- McCarty, Thomas Vere
The North Atlantic zone of Costa Rica is an alluvial plain, whose fairly good soils and warm, extremely wet climate generate serious weed problems in cultivated crops and pastureland. Basic foods - corn, beans, rice and yuca - are important small farm crops. New land is still being opened for small farming, encouraged by a government-sponsored homesteading program. Research was initiated in 1976 by the International Plant Protection Center, in cooperation with CATIE, to determine whether the weed control practices currently used by small farmers could be improved. Agronomic results indicate that tilling the soil gives no advantage over the farmers present no-tillage methods. Pre-plant treatments with the herbicides glyphosate and paraquat have been shown to save labor in corn crops. There is little evidence that the new treatments raise corn yields. A survey of small farmers was conducted in the region in 1977 and 1978. A random sample of 21 farmers were selected for interviews. The information included a general description of each farm family and the complete farm operation and detailed descriptions of cultural practices in corn and beans crop, with special emphasis on weed control. Social and economic information was also obtained. Small farms in the sample are in various stages of development. The first step is usually to brush out the native timberland and fence off areas for a few cattle to graze. Then parcels are cleared for annual crops, especially corn, which is the most dependable cash crop. The farmer rotates parcels for annual crops, weedy fallow and pasture. He constantly attempts to build up his beef herd. Development of perennial plots is limited by the quantities demanded for home and local use. Nearly half the labor, and half the cash resources, expended in corn production are for weed control. The farmers typically cut the weeds with machete and leave the vegetation as mulch before planting, weed the crop with machete or with very light applications of 2,4-D, and cut the weeds once more with machete before doubling the ears and harvesting. Some temporary local shortages of labor occur in the peak periods, when harvesting for one season overlaps with soil preparation and planting for the next, although general underemployment prevails in the long slack periods. Weed conditions influence greatly the quantities of labor used for weed control. Rottboellia exaltata is the most noxious weed in corn cropping. The quantitative information from the survey was tabulated in partial budgets or detailed accounting sheets of variable costs and revenues, for corn parcels on each sample farm. Analysis of variance and regression models were used to test hypothetical relationships among the variables. These results were then compared with estimated capabilities and costs of the experimental weed control treatments for the corn crop on each sample farm. Reported wage rates and calculated returns to family labor were used to estimate the values of family labor. It was found that a minority of the small corn farmers - those who currently use relatively high quantities of cash resources - might be able to reduce costs with the new treatments, without losing revenue. Their increases in cash income would not always exceed the losses in gainful employment suffered by the farmworkers. For the majority of small farmers in the region - those who raise corn with family labor as the main resource - the new treatments do not appear to offer any economic advantages. The treatments are expensive, they offer little promise for raising yields, and their labor-saving effects do not fall squarely in the peak labor periods. It is suggested, therefore, that recommendation of the new treatments should be subject to the farmers' financial conditions and to their actual objectives in growing corn. The use of soil samples and research in the control of pasture weeds are also suggested for further research by the IPPC. Finally, it is suggested that assistance in the development of extra-local banana markets for small farmers might be of great value.