Summary When conditions for N losses were high SD and CRN management strategies were superior. Under extremely warm conditions some CRN technologies have the potential to cause stand reduction. Under some production scenarios, the use of CRN strategies were economically favorable.
Thermal detector aerial image collected on Oct. 23, 2001
Highly Organic Clay Clay Loam Silt Loam Loam Sandy Loam Loamy Sand Sand Soil Texture Variation in Lettuce Field
02004006008001000 1200 Distance (ft) 0 200 400 600 D i s t a n c e ( f t ) Volumetric Soil moisture before irrigation on Oct. 18 2001
020040060080010001200 Distance (ft) 0 200 400 600 D i s t a n c e ( f t ) GPS referenced lettuce yield in Imperial Valley
Summary N uptake patterns are useful for developing efficient N management strategies Depending on the production scenario, split sidedress N application, fertigation, and CRN are all viable options for enhancing fertilizer use efficiency Soil and plant testing can be useful in guiding post plant N applications Efficient Irrigation is an important prerequisite for efficient N management
Summary P added to soil is quickly rendered insoluble. Both physical sorption and precipitation reactions appear to be involved. At high soil pH values P fixation is associated with the carbonate fraction. Soil temperature can influence P availability to crops under some circumstances.
Summary (continued) Soil and plant tissue tests are viable tools for P management of vegetable crops. The P fertilizer required should be applied preplant P placement is often an effective management strategy for improving fertilizer use efficiency.
III. Understanding Why Crops in the Desert Rarely Respond to K Fertilization
Properties of Selected Soils Soil SeriesTotal K (g kg-1) Exchangeable K (mg kg-1) Clay Mineralogy Antho22.0366S>MI>K Gilman21.1280S>MI>K Glenbar20.1257S>MI=K>Q Grabe24.8549S>MI>K=CA Indio17.3315S>MI=K>Q Pima26.0430S>MI K Q Casa Grande29.9560S KMI=K=PG>Q Gadsden18.1460S>MI=K>Q S-SMECTITE; MI-MICA; K-KAOLINITE; Q-QUARTZ; CA-CALCITE;PG-LYGORSKITE
Calculated Sufficiency and K Desorption Soil SeriesSufficiency Level K (mg kg -1 ) Difference between Exchangeable and Sufficiency (mg kg -1 ) K Desorbed Per 30 min. (mg kg -1 ) Antho14322318 Gilman13614417 Glenbar13811915 Grabe17137816 Indio15815712 Pima16926113 Casa Grande13742333 Mohall14116816 Superstition120-2011 Gadsden17328713
Summary of Clay Mineralogy Clay mineralogy was a mixed composition of smectitie, mica, kalonite, palygorskite, calcite, and quartz. All soils contained K bearing mica, typically associated with high K release rates. These soils contained negligiable amounts of vermiculite, known for a high capacity to fix K.
Comparison of K Applied in Irrigation Water and Amount Accumulated by Crop CropIrrigation K (kg ha -1) Crop Accumulation (kg ha -1) Broccoli50238 Melon52176 Carrots42409 Lettuce21192 Onions59196 Sweet Corn50119
Celery (Harmer and Benne, 1945; Harmer et al. 1953). Cabbage (Costigan and McBurney, 1983; Costigan and Mead, 1987). Lettuce (Pereira and Westerman, 1978; Burns, 1986; Burns and Hutsby, 1986; 1987; Costigan and Mead, 1987). Tomatoes (Figdore et al., 1987;1989). Other Vegetable Crops Showing Responses to Na when K Limiting
Sodium Applied in Irrigation Water CropIrrigation Water (cm) Irrigation Na (kg ha -1) Broccoli55719 Melon60785 Carrots62806 Lettuce27355 Onions791030 Sweet Corn60780 Irrigation =ET/(1-LR)
Summary Many agricultural soils in the southwestern desert have soil test K levels sufficient for optimal crop production. Many agricultural soils have a high capacity to replenish K to the soil solution and exchange sites due to their clay content and clay mineralogy. Irrigation water used in the area has the potential to contribute significant amounts of K (and Na) for crop production. In addition, Na can partially substitute for K for some important crops produced in the region.