Improving Soil Quality to Increase Yield and Reduce Diseases in Organic Rice Production

Improving Soil Quality to Increase Yield and Reduce Diseases in Organic Rice Production

Summary

We have completed our third year of this project to determine the impact of winter cover crops, soil amendments, and rice varieties on organic rice production at Beaumont, TX and Charleston, South Carolina. In Texas, the 2013-14 winter cover crops were established. The amounts of dry biomass were 4,525 and 5,152 kg/ha for clover and ryegrass, respectively. The cover crop yields were comparable to these in 2013 but lower than 2012. Due to poor rice stands, replanting was conducted in 2014 but in a field without the effect of winter cover crops. Rice variety had a significant effect on all tested aspects of rice production. Tesanai had higher grain yield and 1,000 grain weight than Presidio and XL753. The averaged grain yields for Tesanai, XL753, and Presidio were 9,949, 8,614, and 6,505 kg/ha, respectively. Compared to conventional cultivars, the hybrid, XL753, had greater spikelets per panicle and filled grain per panicle than Tesanai and Presidio. Although there was a trend for increasing yield with nitrogen application, it was not statistically significant. However, application of soil amendments reduced the severities of narrow brown leaf spot and brown spot on the susceptible variety, Presidio compared to the nonamended fertilizer control. Also, rice cultivars varied in susceptibility to diseases with the lowest in the hybrid and highest in Presidio. No symptoms of straighthead were observed in plots with any treatments. Thus, as seen in previous years, although fertilizer amendments may have some positive impact on yield and disease control, these are not consistent nor likely economically cost effective. Choice of variety is much more important in optimizing yield and minimizing disease pressure. Moreover, an economic analysis based on our field results and farmer-survey indicated that production costs are not as much an issue for organic rice as for conventional rice due to use of fewer costly inputs in organic production systems. Profitability does however hinge on obtaining a guaranteed monetary premium. In addition, having good control of irrigation resources for weed control is necessary for achieving profitability in organic rice production. In South Carolina, six varieties were tested in 2014. As in TX, Tesanai and XL753 had significantly higher yield than other cultivars (10,842 ~ 11,399 kg/ha) demonstrating that research results are applicable between these two southern locations.

Objectives/Performance Targets

Texas

• Establishment of cover crop trials and determine the above ground biomass of clover and ryegrass at termination and their N content,

• Conduct field trial to determine cover crop, rice variety, and soil amendment application on organic rice production, grain yield, and milling quality, and

• Monitor the effects of cover crop, rice variety, and soil amendment application on rice disease occurrence.

South Carolina

• Establish an organic rice field testing site and expertise at the Clemson Coastal Research and Extension Center (CCREC),

• Evaluate yield potential of 6 rice varieties under organic management,

• Identify yield limiting production issues, and

• Compare results from the SC trial and previous trials in TX to determine how transferable results are between the two states.

Accomplishments/Milestones

Beaumont, Texas

Cover crop production: Two selected winter cover crops, Durana white clover and ryegrass, were planted on November 6, 2013. Both cover crops were terminated on March 14, 2014 and the fallow field of indigenous weeds, ryegrass, and some clover was cultivated. The amount of dry biomass at termination was 4,525 and 5,152 kg/ha for clover and ryegrass, respectively. The average moisture at harvest was around 81%. The biomass yields were comparable to those in 2013 but lower than 2012. After termination, the cover crops were left for three weeks to decompose prior to incorporation. Our previous research has shown this is important to mitigate potential straighthead (physiological disease) occurrence in the subsequent organic rice crop.

Organic rice production: In the 2014 Beaumont field trials, we continued to examine cover crops (Durana white clover, ryegrass, and fallow), soil amendments (Nature Safe vs. Rhizogen) with three levels (untreated control, 150 kg N/ha, and 210 kg N/ha), and three rice varieties (Tesanai – high yield, used for flour market, Presidio – superior long grain quality, and XL753 – high yield, new released hybrid that was suggested by the Organic Rice Production Advisory Board) on rice production. Winter cover crop treatments served as main plots with rice varieties as sub-plots. Soil amendment treatments were applied as sub-sub-plots. Each treatment had four replications. Cover crops were managed as in the previous section. Soil amendments were broadcast by hand and incorporated just after planting using a rake in the drill-seeded plots that were approximately 5 m^-2. Plots were flush irrigated to encourage uniform germination and after stand establishment were maintained under a flood until harvest to help with weed control. In addition, we treated all the seed with OMRI certified gibberellic acid (GA) to promote seed germination. Organic rice was drill seeded on April 22, 2014 using a high seeding rate (160 kg/ha for Presidio and Tesanai, and 80 kg/ha for XL753 which is double the recommended rate for hybrids). Although the three varieties were successfully planted, the sudden drop in temperature severely impacted the emergence of rice seed which caused very poor stands; therefore, the trials were terminated.

We replanted the organic rice trial at a different part of the organic field but which had not been planted with cover crops in the previous fall. Thus, in the new plots (trials) we only tested the effect of cultivar and nitrogen rate on organic rice production.

Rice variety had a significant effect on all tested aspects of rice production (Table 1). Tesanai had higher grain yield and 1,000 grain weight than Presidio and XL753 (Table 2). The averaged grain yields for Tesanai, XL753, and Presidio were 9,949, 8,614, and 6,505 kg/ha, respectively. Compared to conventional cultivars, the hybrid, XL753, had greater spikelets per panicle and fertility per panicle than Tesanai and Presidio. Presidio had higher milling yield and percentage of filled grain on the panicle than the other cultivars and was not significantly different from XL753 for harvest index (Table 2).

There were no significant differences among the nitrogen applications (Table 1) although there was a trend for increased rice grain yield, milling quality, percentage of filled grain, and harvest index with the split application of nitrogen as compared to the control (Table 3).

Disease monitoring:

A trial was established in a certified organic field at Beaumont, TX in 2014 to evaluate the effects of rice cultivar and soil fertilizer amendment on the severities of narrow brown leaf spot, brown spot, and straighthead. Application of Rhizogen at either 90+60 (N two way split) or 150 kg N/ha (one time at planting) equally reduced the severities of narrow brown leaf spot and brown spot on Presidio compared to the nonamended fertilizer control (Table 4). Application of the fertilizer at either 90+60 or 150 kg N/ha also reduced brown spot severity on XL753. Severity of narrow brown leaf spot was highest (3.5 on a scale of 0 to 9) on Presidio, least (0.8) on XL753, and in intermediate (2.0) on Tesanai. Tesanai (1.5) has a significantly lower severity of brown spot than Presidio (3.0) and XL753 (2.7). No symptoms of straighthead were observed in plots with any treatments. The results of this field study indicate that resistant cultivars such as Tesanai and XL753, optimum fertilizer N level and cover crop can be effective tools to reduce the damage caused by diseases in organic rice.

Economic Summary:

Little is known about the costs associated with organic rice production. In 2014, production costs for organic rice were estimated for key counties producing organic rice in Texas and were compared with those for conventional rice. Crop budgets for both organic and conventional rice are reported in Table 5, and breakeven yields necessary to cover total specified organic rice production costs for varying organic rice prices are reported in (Table 6). The budget results were presented to participants of an organic rice workshop held July 10, 2014 at the Beaumont, Texas Rice Field Day. The presentation was entitled “Economics of Organic Rice Production.”

The budgetary analysis indicated production costs are not as much an issue for organic rice as for conventional rice due to use of fewer costly inputs in organic production systems. Achieving yields comparable with conventional rice is also not as much a profitability issue due to the higher prices received for organic rice relative to conventional rice. In short, organic rice producers do not need to have conventional rice yields to achieve profitability.

Profitability does however hinge on obtaining a guaranteed monetary premium. Prices for organic rice can be double those obtained for conventional rice, but the producer must have a buyer already at hand to obtain the premium. The guaranteed premium is obtained either through a contract with an organic rice mill or through vertical integration (growing rice, milling and packaging it, and selling at retail to identified buyers). The premium will likely be based on the variety or varieties desired by the buyer, and this can make the task of growing organic rice more difficult.

Having good water availability is also necessary for achieving profitability in organic rice production. Flood is the most effective means of controlling weeds and diseases in organic rice production, as organic producers cannot use conventional pesticides. The organic rice producer needs both a consistent source of water and good control in moving water across the field. Precision leveling may be necessary to achieve the water control necessary for most organic rice systems, and this will likely be an additional initial capital expense.

Plans are underway to conduct a similar budgetary analysis for organic rice production in Arkansas in 2015. Organic rice production costs will be developed based on input from organic growers in both Arkansas and Missouri. Plans are also underway to evaluate the economics of incorporating cover crops, alternative soil amendments, and different varieties in organic rice systems.

Charleston, South Carolina

Fall of 2013, a certified organic field located at the Clemson Coastal Research and Extension Center, with organic matter of approximately 7% was disked twice, leveled and seeded with ‘White Dutch Clover’ (Trifolium repens) at 12 lbs/Ac (13.4 kg/ha). In the spring 2014, the field was flail mowed and disked multiple times. Based on soil test results, Nature Safe 8-5-5 fertilizer was broadcast at 160 Units N/Ac, tilled into the soil profile and then flooded. On May 9, 2014 pregerminated seed of six rice cultivars: Carolina Gold, Charleston Gold, Presidio, Tesanai II, IAC 600, and XL 753 were broadcast in plots 9.3 m². A completely randomized block design with four replications was used. After the rice was pegged, the field was re-flooded. However the study was completely lost due to weeds and had to be replanted in the same manner on June 6, 2014. Serenade Max (Bacillus subtilis. strain QST 713) was applied every 1 or 2 weeks throughout the season for disease control. Days to flowering, heading and height data were collected prior to harvest. At harvest, 0.03 m² area plot subsamples were hand harvested and graded for narrow brown leaf spot, brown leaf spot, bacterial panicle blight and straight head. The graded bundles were then hung in a drying greenhouse for approximately 36hrs until rice kernels achieved 12% moisture and then the bundles were threshed with a Kincade plot combine and then weighed. Plot yields were then shipped to USDA Agricultural Research Service, Dale Bumpers National Rice Research Center, to determine milling quality.

Field yields per acre were as follows;1) Carolina Gold = 2,809, 2) Charleston Gold = 7,434, 3) Presidio = 6,913, 4) Tesanai = 11,399, 5) IAC 600 = 3,927, and 6) XL753 = 10,842. Tesanai and XL753 had significantly higher yields than the other four cultivars. Charleston Gold and Presidio had similar yields and were significantly greater than IAC 600 and Carolina Gold which were not significantly different from one another. All but IAC 600 (purple bran variety) were milled to determine whole milling yields. The chart demonstrates crop value (whole grain rice x yield per acre) using head rice yields, except for IAC 600 which is presented as brown (hulled) rice yield (Fig. 1). These results demonstrate wide differences in economic yields among the varieties.

Of the three years the study was conducted, yields were greater in 2014 than the other two. There were no significant differences for disease pressure and physiological disorders (i.e. straighthead) with ranking of severity generally not exceeding 0.75 on a 0-5 scale. Although weed pressure early caused an initial crop failure in 2014 resulting in replanting, the weeds that were present in the final stands did not result in a noticeable loss in yields. Based on the past three years of data, recommendations are now being made to growers in South Carolina and there has been a rise in conventional rice production as well as transitional and organic rice acreage. Further work is needed for cultivar trials to further this progress in South Carolina.

• Table 2. Cultivar Effect on Organic Rice Production under Fallow.
• Table 4. Effects of application of N levels of Rhizogen on the severity of narrow brown leaf spot (NBLS) and brown spot on Presidio, Tesanai and XL753 in 2014.
• Table 1. Significance of the main effects of seeding rate and cultivar and interactions among the main effects for organic rice production.
• Table 5. Estimated costs, conventional versus organic rice, Jefferson-Liberty Counties in Texas, 2013.
• Fig. 1. Crop value of different cultivars grown under organic production in Charleston, SC 2014.
• Table 3. Nitrogen Rate Effect on Organic Rice Production Following Fallow.
• Table 6. Break-even yields required to cover total specified costs at varying rice prices, organic rice, Jefferson-Liberty Counties in Texas, 2013.

Impacts and Contributions/Outcomes

Our results have been presented at scientific conferences, field days, extension meetings, and scientific journal. During our 2014 field day, an organic rice workshop at the Texas A&M AgriLife Research Center at Beaumont attracted more than fifty (50) rice producers, county agents, millers, industrial consultants, and researchers. At the 2014 ASA-SSSA-CSA annual meeting, two PIs gave talks on organic rice production which attracted more than one hundred (100) in the audience. Additional presentations were made by all PI’s at the Rice Technical Working Group meeting in February 2014. In addition, William Tarpley, a college student, participated in this program for his intern training to gain experience in sustainable agriculture and presented a poster to the S-SARE supported by the Southern SARE Young Scholar Enhancement Program.

• Dou, F., X. G. Zhou, A. M. McClung, J. Storlien, Y. Lang, A. Torbert, F. Hons, B. Ward, S. Kresovich, and J. Wight. 2014. Cover crop, soil amendments, and variety effects on organic rice production in Texas. 35rd Rice Technical Working Group Meeting. New Orleans, Louisiana, USA. Feb. 18-21, 2014. P. 119-120.

• Dou, F. 2014. Summary of 2013 organic rice production. Presentation made at the Organic Rice Workshop of the 67th Annual Beaumont Field Day. Beaumont, TX, July 10, 2014.

• Zhou, X. 2014. Effects of cover crops, fertility, and cultivars on organic rice diseases. Presentation made at the Organic Rice Workshop of the 67th Annual Beaumont Field Day. Beaumont, TX, July 10, 2014.

• McClung, A.M. 2014. Impact of variety and organic production methods on yield, quality, and grain arsenic. Presentation made at the Organic Rice Workshop of the 67th Annual Beaumont Field Day. Beaumont, TX, July 10, 2014.

• Watkins, K.B. 2014. Economics of organic rice production. Presentation made at the Organic Rice Workshop of the 67th Annual Beaumont Field Day. Beaumont, TX, July 10, 2014.

• Ward, B. 2014. System of Rice Intensification Cultivar Trials 2014. Presentation made at the Organic Rice Workshop of the 67th Annual Beaumont Field Day. Beaumont, TX, July 10, 2014.

• Dou, F., Zhou, F. Hons, A.M. McClung, S. Wang, Y. Lang, G. Li, J. Storlien, J. Wight, K. Landry, and G. Liu. Improving organic rice production through combining cover crop, soil amendment, and variety selection. The 67th Annual Beaumont Field Day. Beaumont, TX July 10, 2014.

• Dou, F., F. Hons, X. Zhou, A. McClung, S. Wang, A. Torbert, Y. Lang, G. Li, J. Storlien, and J. Wight. 2014. Effects of cover crop and soil amendment on organic rice production. Annual Meeting of the Soil Science Society of America. Long Beach, CA. November 2014.

• McClung, A.M., Gerads, R., Chaney, R.L., Dou, F., Zhou, X., Duke, S.E. November 2-5, 2014. Organic rice production: minimizing exposure to grain arsenic. ASA-CSSA-SSSA Annual Meeting Abstracts, Long Beach, CA. 61-4.

• Storlien, J., F. Dou, G. Liu, and F. Hons. 2014. Organic rice management effects on greenhouse gas emissions in southeast Texas. Annual Meeting of the Soil Science Society of America. Long Beach, CA. November 2014.

• Chen, Ming-Hsuan and McClung, Anna. 2015. Effects of cultivars, organic cropping management, and environment on anti-oxidants in whole grain rice. Cereal Chemistry (accepted  March 17, 2015).

Collaborators: