Linda Benedict, Deliberto, Michael, Linscombe, Steven D., Salassi, Michael | 9/12/2013 1:30:59 AM
Michael E. Salassi, Steven D. Linscombe and Michael A. Deliberto
Crop lodging is a condition under which plant stems at the base of a crop plant weaken to the point of no longer being able to support the weight of the upper portion of the plant, causing it fall in the field. Lodging usually occurs in grain crops when the plant is mature and with filled grain heads, in the days or weeks before harvest. It is usually the result of adverse weather conditions from high winds and pounding rain. Although incidences of crop lodging can vary greatly from year to year or farm to farm, lodging of rice plants in Louisiana is a significant factor to contend with in the production of a rice crop.
The variation in physical plant structural characteristics among rice varieties directly influences the optimal production practices best suited to individual rice varieties or groups of similar rice varieties. Relationships among plant characteristics – including plant height, stem strength and potential grain yield – interact with production practices to significantly influence a rice plant’s ability to remain standing in the field at crop maturity and be easily harvested, despite high grain yields. The production practices include date of planting, seeding rates and fertilization rates. As a result, considerable research at the LSU AgCenter’s Rice Research Station is devoted to developing rice varieties t that grow well in Louisiana with some level of plant structure resistance to lodging at high grain yields.
Although usually not widespread in a field, lodging can result in significant yield losses. It has been generally known that lodging adversely affects rice grain quality and eventual market price. However, no specific research studies have been conducted recently in the southern U.S. rice-growing region to document the relational impact of lodging on rice milling quality and on the resulting market price received from the sale of the rough rice.
In 2011 and 2012, the LSU AgCenter led a four-state research project to specifically evaluate and document the economic consequences of rice lodging on rice milling yield and rough rice market price. Field trials evaluating lodging impacts on several rice varieties commonly grown in the southern U.S. rice-growing region were conducted at the LSU AgCenter Rice Research Station in Crowley, the Mississippi State University Delta Research and Extension Center in Stoneville, the University of Arkansas Rice Research Station in Stuttgart, and the Texas A&M University Rice Research Station in Eagle Lake. These four study locations represent the range of rice-growing environments and conditions typical for southern U.S. rice production.
Three lodging treatments were evaluated in this study: early lodging, late lodging and standing (no lodging). For the early and late lodging treatments, the rice crop was manually lodged in the plots at a specified time in relation to harvest. The timing of early lodging occurred when the rice panicles were first observed turning yellow (approximately five to seven days prior to field drainage). The timing of late lodging occurred approximately one week prior to harvest maturity. For the standing treatment to be used as a check, no lodging was conducted. Two planting dates were also evaluated in the study. The first planting date was at the earliest typical planting date for the specific production area and the second planting date was approximately 30 days later. For the study in Louisiana, these planting dates were approximately March 15 and April 15 of each year.
Several rice varieties were evaluated for each lodging treatment and planting date at each location. For the test location in Louisiana, the following seven rice varieties were evaluated: CL151, Cheniere, Presidio, Jupiter, Wells, Cocodrie and LAH10. The majority of these varieties are long-grain rice varieties. CL151 is a long-grain herbicideresistant Clearfield variety. Cheniere, Presidio, Wells and Cocodrie are conventional long-grain rice varieties. Jupiter is a conventional medium-grain rice variety, and LAH10 is a hybrid rice variety. Estimates presented here are from the results of the project, averaged over all rice varieties evaluated, for the two years of the study conducted at the Rice Research Station in Crowley, La.
Rice milling yield is estimated as the proportional quantity of whole rice kernels and total milled rice (whole kernels and broken kernels combined) produced in the milling process of rough rice. A standard rough rice milling yield reference value can be stated as a “55/70” milling yield. This value implies that the milling of 100 pounds of rough rice yielded 55 pounds of whole kernel milled rice, commonly referred to as head rice yield, and 70 pounds of total milled rice grain, with the difference being 15 pounds of broken kernel milled rice. Rice milling yield is directly affected by factors that can lead to the breakage of rice kernels during the milling process. One of the primary factors is the moisture content of the rough rice at the time of milling. Research conducted at the Rice Research Station identifies the optimal harvest moisture content for rice varieties that would minimize the breakage of rice kernels during the milling process. Crop lodging just prior to harvest, which could cause grain moisture content in the affected plants to either rise above or fall below optimal grain moisture ranges because of weather conditions at the time of harvest, would be expected to directly affect rough rice milling yield.
Rough rice milling yields from the lodging studies conducted at the AgCenter Rice Research Station are presented in Figure 1. For both rice planting dates evaluated, the reduction in both head rice milling yield and total grain milling yield from crop lodging was found to be statistically significant from the nonlodged standing crop. In the early planting date trial, rough rice milling yields were 50.2/67.6 and 51.1/67.5 for the early and late lodged treatments compared with a nonlodged standing crop milling yield of 56.0/68.9. Corresponding milling yields for the late planting date trial were 50.3/66.8 and 52.0/66.6 for the early and late lodged treatments compared with a milling yield of 53.4/67.8 for the nonlodged standing crop.
Milling yield has been shown to be a significant factor in establishing the market price for specific lots of rice. Whole grain milled rice is most commonly sold for direct food use as a stand-alone product, while broken grain rice is sold for use in more processed foods. Because of this differential product demand, whole grain rice commands a higher price in the market compared with broken grain rice. Distinct from other grains, the milling yield for rice must also be included to completely specify the market price (value) of a specific sample of rice. In the lodging study conducted at the Rice Research Station in 2011 and 2012, the effects of crop lodging on rice milling yields were estimated to reduce the market price received for the rough rice by an average of $0.28 to $0.60 per hundredweight (Figure 2). Assuming an average rough rice harvest yield of 6,500 pounds per acre, the adverse consequences of lodging on rough rice market price alone can reduce crop revenue from the affected area by an average of $18 to $39 per acre.
Lodging of rice plants, oftentimes caused by adverse weather before crop harvest, although sporadic in occurrence and severity, can represent a significant reduction in crop net returns. Reduction in crop yield, decrease in market price and increase in harvest cost all combine to reduce net returns in areas of rice fields affected by lodging. As new farm risk management tools, particularly in the area of crop insurance, are developed for use by rice producers to manage crop production and market price risk in the future, being able to quantify the probability of occurrence and likely magnitude of the effects of adverse conditions on crops is critical to the development of risk management programs which would protect producers from adverse weather impacts on crops such as lodging. Results from this two-year lodging study will provide useful information to the rice industry as new crop risk management tools are developed for use by rice producers in managing crop production risks.
Michael E. Salassi is J. Nelson Fairbanks Professor and Michael A. Deliberto is a research associate in the Department of Agricultural Economics & Agribusiness. Steven D. Linscombe is American Cyanamid Professor for Excellence in Plant Genetics, Breeding and Variety Development at the Rice Research Station, Crowley.
(This article was published in the summer 2013 issue of Louisiana Agriculture magazine.)