The Salinas Valley along the central coast of California produces more than 100,000 ha of cool-season vegetables per year. The mild Mediterranean climate allows an extended growing season, and production of two to three crops per year is the norm. With little precipitation during the main production season (March–November), frequent irrigation is required. Fields are typically fallow during the winter when most of the annual precipitation occurs. This intensive production system has led to serious environmental problems. Nitrate contamination of groundwater has become widespread; it has been estimated that NO3-N loading to groundwater exceeds 100 kg·ha−1·yr−1 (Rosenstock et al., 2014). Additionally, excessive extraction of groundwater for irrigation has resulted in significant seawater intrusion, endangering aquifers used for both irrigation and urban needs (Harter, 2015).
Extensive research has been conducted to improve N fertilization and irrigation management of lettuce (Lactuca sativa L.), the predominant crop in this region (Bottoms et al., 2012; Breschini and Hartz, 2002; Hartz et al., 2000; Jackson et al., 1994). Less attention has been given to cole crops (broccoli, cabbage, and cauliflower), which are important rotational crops. Cole crops represent both an opportunity and a challenge. They are relatively deep rooted (Greenwood et al., 1982; Thorup-Kristensen, 2001), have the ability to take up more than 300 kg N/ha (Bakker et al., 2009b; Bowen et al., 1999; Thompson et al., 2002a), and consequently may be able to scavenge residual SMN from a substantial depth. Conversely, a large amount of N is contained in crop residue after harvest, and rapid mineralization from this N-rich residue has been recognized as a nitrate leaching hazard (Bakker et al., 2009b; Congreves and Van Eerd, 2015; Everaarts, 2000).
Yield-maximizing N fertilization rates for cole crops have been reported to range from <150 to >400 kg·ha−1 (Bakker et al., 2009a; Bowen et al., 1999; Cutcliffe and Munro, 1976; Kahn et al. 1991; Sorenson, 1999; Thompson et al., 2000a, 2002a; Zebarth et al., 1991). This wide range undoubtedly reflects differences among studies in field environment, soil fertility, plant population, and yield potential. Residual SMN has been recognized as a major determinant of the N fertilizer requirement of cole crops (Bakker et al., 2009b; Everaarts and van den Berg, 1996; Heckman et al., 2002; Zebarth et al., 1995). In an intensive production system like that of the Salinas Valley, where high levels of residual SMN are common (Bottoms et al., 2012; Breschini and Hartz, 2002), efficient N management requires consideration of field-specific factors rather than prescriptive recommendations.
Irrigation management is closely linked to N efficiency in cole crop production (Thompson et al., 2000b, 2002b). Marketable yield is maximized by maintaining relatively low soil moisture tension (10–25 kPa; Smittle et al., 1994; Thompson et al., 2000a, 2002a), but irrigation in excess of crop evapotranspiration (ETc) can result in significant NO3-N leaching in heavily fertilized fields. Documentation is lacking on cole crop irrigation requirements under coastal California conditions, and on current irrigation practices.
Improved cole crop N management requires a more complete understanding of soil and crop N dynamics of these crops within the intensive crop production scheme of this region. This study was undertaken to document cole crop growth, rooting depth, N uptake and partitioning, and patterns of soil N availability in representative commercial fields of the Salinas Valley.
Agneessens, L., Viaene, J., Vanden Nest, T., Vandecasteele, B. & De Neve, S. 2015 Effect of ensilaged vegetable crop residue amendments on soil carbon and nitrogen dynamics Scientia Hort. 192 311 319
Bakker, C.J., Swanton, C.J. & McKeown, A.W. 2009a Broccoli growth in response to increasing rates of pre-plant nitrogen. I. Yield and quality Can. J. Plant Sci. 89 527 537
Bakker, C.J., Swanton, C.J. & McKeown, A.W. 2009b Broccoli growth in response to increasing rates of pre-plant nitrogen. II. Dry matter and nitrogen accumulation Can. J. Plant Sci. 89 539 548
Bottoms, T.G., Smith, R.F., Cahn, M.D. & Hartz, T.K. 2012 Nitrogen requirements and N status determination of lettuce HortScience 47 1768 1774
Bowen, P.A., Zebarth, B.J. & Toivonen, P.M.A. 1999 Dynamics of nitrogen and dry-matter partitioning and accumulation in broccoli (Brassica oleracea var. italica) in relation to extractable soil inorganic nitrogen Can. J. Plant Sci. 79 277 286
Breschini, S.J. & Hartz, T.K. 2002 Presidedress soil nitrate testing reduces nitrogen fertilizer use and nitrate leaching hazard in lettuce production HortScience 37 1061 1064
Chaves, B., De Neve, S., Boeckx, P., Van Cleemput, O. & Hofman, G. 2007 Manipulating nitrogen release from nitrogen-rich crop residues using organic wastes under field conditions Soil Sci. Soc. Amer. J. 71 1240 1250
Congreves, K.A., Vyn, R.J. & Van Eerd, L.L. 2013 Evaluation of post-harvest organic carbon amendments as a strategy to minimize nitrogen losses in cole crop production Agronomy 3 181 199
Cutcliffe, J.A. & Munro, D.C. 1976 Effects of nitrogen, phosphorus and potassium on yield and maturity of cauliflower Can. J. Plant Sci. 65 127 131
De Neve, S. & Hoffman, G. 1996 Modelling N mineralization of vegetable crop residues during laboratory incubations Soil Biol. Biochem. 28 1451 1457
De Neve, S., Dieltjens, I., Moreels, E. & Hoffman, G. 2003 Measured and simulated nitrate leaching on an organic and a conventional mixed farm Biol. Agr. Hort. 21 217 229
de Ruijter, F.J., ten Berg, H.F.M. & Smit, A.L. 2010 The fate of nitrogen from crop residues of broccoli, leek and sugarbeet Acta Hort. 852 157 161
Everaarts, A.P. 1993 Strategies to improve the efficiency of nitrogen fertilizer use in the cultivation of Brassica vegetables Acta Hort. 339 161 173
Greenwood, D.J., Rahn, C., Draycott, A., Vaidyanathan, L.V. & Paterson, C. 1996 Modelling and measurement of the effects of fertilizer-N and crop residue incorporation on N-dynamics in vegetable cropping Soil Use Mgt. 12 13 24
Hartz, T.K., Bendixen, W.E. & Wierdsma, L. 2000 The value of presidedress soil nitrate testing as a nitrogen management tool in irrigated vegetable production HortScience 35 651 656
Heckman, J.R., Morris, T., Sims, J.T., Sieczka, J.B., Krogmann, U., Nitzsche, P. & Ashley, R. 2002 Pre-sidedress soil nitrate test is effective for fall cabbage HortScience 37 113 117
Hofer, S. 2003 Determination of ammonia (salicylate) in 2M KCl soil extracts by flow injection analysis. QuikChem Method 12-107-06-2-A. Lachat Instruments, Loveland, CO
Jackson, L.E., Stivers, L.J., Warden, B.T. & Tanji, K.K. 1994 Crop nitrogen utilization and soil nitrate loss in a lettuce field Fert. Res. 37 93 105
Johnson, L., Cahn, M., Martin, F., Benzen, S. & Farrara, B. 2016 Evapotranspiration-based irrigation scheduling of head lettuce and broccoli HortScience 51 935 940
Kahn, B.A., Shilling, P.G., Brusewitz, G.H. & McNew, R.W. 1991 Force to shear the stalk, stalk diameter and yield of broccoli in response to nitrogen fertilization and within-row spacing J. Amer. Soc. Hort. Sci. 116 222 227
Knepel, K. 2003 Determination of nitrate in 2M KCl soil extracts by flow injection analysis. QuikChem Method 12-107-04-1-B. Lachat Instruments, Loveland, CO
Krusekopf, H.H., Mitchell, J.P., Hartz, T.K., May, D.M., Miyao, E.M. & Cahn, M.D. 2002 Pre-sidedress soil nitrate testing identifies processing tomato fields not requiring sidedress N fertilizer HortScience 37 520 524
Lemaire, G. & Gastal, F. 1997 N uptake and distribution in plant canopies, p. 3–41. In: G. Lemaire (ed.). Diagnosis of nitrogen status in crops. Springer-Verlag, Berlin, Germany
Little, G.E., Hills, D.J. & Hanson, B.R. 1993 Uniformity in pressurized irrigation systems depends on design, installation Calif. Agr. 47 3 18 21
Rather, K., Schenk, M.K., Everaarts, A.P. & Vethman, S. 2000 Rooting pattern and nitrogen uptake of three cauliflower (Brassica olearacea var. botrytis) F1-hybrids J. Plant Nutr. Soil Sci. 163 467 474
Rosenstock, T.S., Liptzin, D., Dzurella, K., Fryjoff-Hung, A., Hollander, A., Jensen, V., King, A., Kourakos, G., McNally, A., Pettygrove, G.S., Quinn, J., Viers, J.H., Tomich, T.P. & Harter, T. 2014 Agriculture’s contribution to nitrate contamination of California groundwater J. Environ. Qual. 43 895 907
Thompson, T.L., Doerge, T.A. & Godin, R.E. 2000a Nitrogen and water interactions in subsurface drip-irrigated cauliflower: I. Plant response Soil Sci. Soc. Amer. J. 64 406 411
Thompson, T.L., Doerge, T.A. & Godin, R.E. 2000b Nitrogen and water interactions in subsurface drip-irrigated cauliflower: II. Agronomic, economic and environmental outcomes Soil Sci. Soc. Amer. J. 64 412 418
Thompson, T.L., Doerge, T.A. & Godin, R.E. 2002a Subsurface drip irrigation and fertigation of broccoli: I. Yield, quality and nitrogen uptake Soil Sci. Soc. Amer. J. 66 186 192
Thompson, T.L., Doerge, T.A. & Godin, R.E. 2002b Subsurface drip irrigation and fertigation of broccoli: II. Agronomic, economic and environmental outcomes Soil Sci. Soc. Amer. J. 66 178 185
Vagen, I.M., Skjelvag, A.O. & Bonesmo, H. 2004 Growth analysis of broccoli in relation to fertilizer nitrogen application J. Hort. Sci. Biotechnol. 79 484 492
Willcutts, J.F., Overman, A.R., Hochmuth, G.J., Cantliffe, D.J. & Soundy, P. 1998 A comparison of three mathematical models of response to applied nitrogen: A case study using lettuce HortScience 33 833 836
Wyland, L.J., Jackson, L.E., Chaney, W.E., Klonsky, K., Koike, S.T. & Kimple, B. 1996 Winter cover crops in a vegetable cropping system: Impacts on nitrate leaching, soil water, crop yield, pests and management costs Agr. Ecosyst. Environ. 59 1 17
Zebarth, B.J., Bowen, P.A. & Toivonen, P.M. 1995 Influence of nitrogen fertilization on broccoli yield, nitrogen accumulation and apparent fertilizer-nitrogen recovery Can. J. Plant Sci. 75 717 725
Zebarth, B.J., Freyman, S. & Kowalenko, C.G. 1991 Influence of nitrogen fertilization on cabbage yield, head nitrogen content and extractable soil inorganic nitrogen at harvest Can. J. Plant Sci. 71 1275 1280