Preliminary nitrogen (N) management experiments with spinach, leaf lettuce, romaine collard and mustard were conducted on a Casa Grande s.l. soil at the Maricopa Agricultural Center in the winter and spring of 1990-91. The purpose of this N rate experiment was to develop initial Best Management strategies for N fertilizer use for emerging high value crops grown in Arizona using subsurface drip irrigation. Three rates of urea, ammonium nitrate were applied to each cultivar to provide deficient (N1), adequate (N2) and supraoptimal real (N3) levels of N. All cultivars responded dramatically to the application of N. Fresh weight yields in the N1 and N2 treatments averaged 45 and 53% of the N3 treatment The average N3 yields recorded in these trials were 23.1, 12.8 and 21.8 tons of marketable produce per acre for greens, spinach and leaf lettuce/romaine crops, respectively. Preliminary plant tissue test results indicated that for all five crops, whole plant total N (TN) levels and midrib + petiole NO₃-N and leaf blade TN concentrations in the youngest mature leaf were responsive to differences in soil N supply and show promise as diagnostic N tissue test procedures. The midrib + petiole NO₃-N test appeared to be the best indicator of plant N status throughout the growing season for all five crops studied.

Two field studies were conducted to evaluate metolachlor (Dual®) for preemergence weed control in spinach to provide support to gain registration through the IR-4 program. Dual® at 1.0 to 1.5 lb a.i./A gave acceptable control of London rocket, black mustard, lambsquarters, and knotweed. Nettleleaf goosefoot, cheeseweed, and yellow sweetclover control was not acceptable. In one test, dimethenamid (Frontier® or SAN -582H, Sandoz) controlled London rocket, lambsquarters, knotweed, and goosefoot at 0.25 lb ai. /A and did not control cheeseweed or sweetclover. Spinach was not injured by Dual® or Frontier®.

Several newly introduced insecticides that have potential for use in vegetable crops for aphid control were evaluated and demonstrated very good efficacy against green peach aphid (Myzus persicae). Field testing in spinach showed that CGA-293343 (Novartis) at the two rates tested significantly reduced the number of aphids relative to the untreated check. CGA-215944 (pymetrozine -Novartis) effectively reduced the number of aphids after two applications. Aphistar (RH- 7988 - Rohm and Haas) demonstrated the greatest reduction in the number of aphids per plant after each application. Provado (imidacloprid) and Thiodan (endosulfan) were applied as commercially available standard treatments and effectively reduced the number of aphids relative to the untreated check. Pirimor (pirimicarb) numerically reduced the number of aphids but was not significantly different relative to the untreated check.