Timothy K. Hartz

Extension Specialist/Agronomist 103 Asmundson Hall 530-752-1738 530-752-9659

Education

BS, Bowling Green State University, Biology, 1973
MS, Colorado State University, Horticulture, 1977
PhD, Virginia Polytechnic Institute, Horticulture, 1980

Professional Experience

Extension Specialist, Dept. of Horticulture, Texas A&M Univ., 1981-87
Extension Specialist, Dept. of Botany & Plant Science, UC Riverside, 1988-91
Extension Specialist, Dept. of Vegetable Crops, UC Davis , 1991-Present

Research & Outreach

I conduct an applied research and outreach program to aid California's large, diverse commercial vegetable industry. The overall goal of my program is to help the industry maintain productivity and profitability, while meeting the mounting environmental and political pressure to adopt more sustainable production practices. My research focus is on improving irrigation and fertility management.

California agriculture will face increasing competition for water from urban and environmental interests. Conversion from conventional furrow or sprinkler irrigation to drip irrigation is one approach to improve water use efficiency; currently at least 40,000 ha of vegetables are drip irrigated annually in the state, and the pace of conversion is accelerating. We have studied many aspects of drip irrigation management: irrigation scheduling (Breschini and Hartz, 2002; Hartz, 1993, 1997), fertigation (Hartz et al, 1994) nutrient monitoring (Hartz et al, 1993), modified tillage practices, etc. The results of these investigations have been widely disseminated, and have had substantial impact on the commercial vegetable industry, in California and beyond.

Conventional vegetable production relies heavily on synthetic fertilizer inputs, particularly nitrogen. Inefficient fertilizer use is not only a waste of a non-renewable resource, but also a significant contributor to groundwater pollution. I have worked extensively to document crop nutrient requirements under conventional production practices, and to develop practical diagnostic techniques (for both laboratory and on-farm use) to improve fertility management (Breschini and Hartz, 2002; Hartz et al., 2001 a, b; Hartz et al., 2002). Examples of these diagnostics include: petiole sap analysis for NO3-N, and an alternative soil K test based on the rate of K release.
In my role as Extension Specialist I provide support to industry groups, individual growers, and county-based UC Farm Advisors on a wide range of vegetable production problems. This support takes several forms: diagnosing individual field problems, conducting field trials and demonstrations, organizing field days and educational meetings, etc. The bulk of my activities relate to cucurbits, solanaceous crops, lettuce, and celery.

Selected References

Breschini, S.J. and T.K. Hartz. 2001. Drip irrigation management affects celery yield and quality. HortScience 37:894-897.

Breschini, S.J. and T.K. Hartz. 2002. Presidedress soil nitrate testing (PSNT) reduces nitrogen fertilizer use and nitrate leaching hazard in lettuce production. HortScience 37:1061-1064.

Hartz, T.K. 1993. Drip irrigation scheduling for fresh-market tomato production. HortScience 28:35-37.

Hartz, T.K. 1997. Effects of drip irrigation scheduling on muskmelon yield and quality. Sci. Hortic. 69:117-122.

Hartz, T.K., M. LeStrange and D.M. May. 1993. Nitrogen requirments of drip-irrigated peppers. HortScience 28:1097-1099

Hartz, T.K., R.F. Smith, M. LeStrange and K.F. Schulbach. 1993. On-Farm monitoring of soil and crop nitrogen status by nitrate-selective electrode. Commun. Soil Sci. Plant Anal. 24:2607-2615.

Hartz, T.K., W.E. Bendixen and L. Wierdsma. 2000. Pre-sidedress soil nitrate testing as a nitrogen management tool in irrigated vegetable production. HortScience 35:651-656.

Hartz, T.K., E.M. Miyao, R.J. Mullen and M.D. Cahn. 2000. Potassium fertilization effects on processing tomato yield and fruit quality. Acta Horticulturae 542:127-133.

Hartz, T.K., C. Giannini, R.O. Miller and E.M. Miyao. 2001. Estimating soil K availability for processing tomato production. Commun. Soil Sci. Plant Anal. 33:1389-1400.

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