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Submitted to: Government Publication/Report
Publication Type: Other Publication Acceptance Date: 7/7/2007 Publication Date: 7/23/2007 Citation: Banuelos, G.S. 2007. Organic Broccoli Production can be Optimized to Achieve High Yield and More Efficient Water Use. Government Publication, California Agri. Research Initiative Report, ARF #03-2001, pgs 0-5. Interpretive Summary: Organic agriculture is steadily increasing its acreage throughout California. Water and nitrogen (N) management are major tools for improving crop yields, especially for crops requiring high nitrogen application, e.g., broccoli. Broccoli has a shallow root system which limits its ability to take up water and N from the deeper soil profile. Broccoli growers tend to over apply both N and water to achieve a desired yield, which results in a high risk of nutrient and water loss from the system. Our study examined the influences of different forms of nitrogen side-dresses and irrigation rates on organic broccoli in two different regions of California, USCS farm in Santa Cruz, CA and Harris farm in Five Points, CA. Side-dress treatments consisted of compost only (CO) fish powder (FP), phytamin (BF), phytamin and NaNO3 (SN), and seabird guano (SG); and irrigation rates consisted of 80,100, 150% crop evapotranspiration (Etc). All organic N sidedresses increased broccoli yields at UCSC and to a lesser extent at Harris farm. Overall, we observed a more significant response of crop yield to both N source and irrigation rates at UCSC farm than at Harris farm. The study shows that the application of N side-dress may not be as essential to improve yield on Harris farm with a long history of applying organic amendments whereas the application of N side-dress is essential to a newly-converted organic farm like UCSC. Moreover, precipitation must also be taken into consideration when determining rates of water application in a specific region of California. Technical Abstract: Organic farming is a viable agronomic option in central and north coastal California. Organic agriculture is dependent upon the application of organic amendments for providing nutrients and water management for sustaining successful organic production on a multitude of crops. Our multi-year field study examined the effects of different forms of organic N fertilizers applied as side-dress with different irrigation rates (80,100, 150% Etc) on organically-grown broccoli in two regions of California; Santa Cruz (UCSC farm) and Five Points (Harris farm). Compost only (CO) was applied at 140kg N/ha with an additional 112 kg N/ha applied as side-dress as either fish power (FP), phytamin(BF), Phytamin and NaNO3 (SN), or seabird guano (SG). Yields from UCSC farm had a greater response to all side-dresses and irrigation treatments than yield responses observed at Harris farm. Excessive precipitation reduced potential effects of water treatments at Harris farm. Water use efficiency rates were achieved with 80 and 100% Etc at UCSC farm and with 100% Etc at Harris farm. Our results clearly demonstrate that application of organic N as a side-dress has a much greater impact on yield in newly-converted organic farms like UCSC farm and exerts less of an impact on well-established organic farms like Harris farm. Moreover, water management must be adjusted and modified in accordance to precipitation received at a specific growing site. |
