Nitrogen and Water Rates for Subsurface Trickle-irrigated Romaine Lettuce

Abstract

<jats:p>Two field experiments were conducted with subsurface trickle-irrigated romaine lettuce (<jats:italic>Lactuca sativa</jats:italic> L. cv. Parris Island Cos) during the 1990–92 winter growing seasons in southern Arizona. The objectives were to determine 1) yield and quality response to varying combinations of soil water tension (SWT) and N fertilizer, 2) seasonal patterns of N uptake, and 3) unutilized fertilizer N. During 1990–91, N rates were 35, 120, and 205 kg·ha<jats:sup>–1</jats:sup>. During 1991–92, the experiment was factorial with N levels from 50 to 300 kg·ha<jats:sup>–1</jats:sup> and target SWT levels of 7.0 and 4.0 kPa. Unutilized fertilizer N was the difference between fertilized and nonfertilized plots in total N inputs not harvested in the crop. When excessive irrigation was not applied (SWT between 6.5 and 7.4 kPa), 95% of the maximum crop yield and yield quality (head length and fresh mass) response occurred at N rates of 156 to 193 kg·ha<jats:sup>–1</jats:sup>, with unutilized fertilizer N &lt;60 kg·ha<jats:sup>–1</jats:sup>. Excessive irrigation (4.6 kPa) resulted in lower yields and yield quality and higher unutilized fertilizer N. Romaine accumulated &gt;74% of its total N uptake in the 38 days before harvest. Unutilized fertilizer N increased sharply when adequate N and water rates were exceeded. These results suggest that a target SWT of no wetter than 6.5 kPa is appropriate for subsurface trickle-irrigated romaine lettuce.</jats:p>

Plant Population and Nitrogen Fertilization for Subsurface Drip-irrigated Onion

“…In New Mexico on a sandy loam, with one drip tape per bed (tape to onion row distance of 0.2 m) and irrigations on alternate days, the water application efficiency was 0.45 when the irrigation system was operated for maximum onion yield and to keep the full bed surface wet (Al-Jamal et al, 2001). For caulifl ower (Brassica oleracea L.) (Thompson et al, 2000), collard (Brassica oleracea L.), mustard (Brassica juncea L.), and spinach (Spinacea oleracea, L.) (Thompson and Doerge, 1995b), lettuce (Lactuca sativa L.) (Thompson and Doerge, 1995a), and watermelon (Citrullus lanatus Thumb.) (Pier and Doerge, 1995) drip irrigated daily on a sandy loam in Arizona, irrigating for maximum yield was just below or at the soil water potential that resulted in N leaching.…”

Increasing Water Use Efficiency in Vegetable Crop Production: From Plant to Irrigation Systems Efficiency

“…Use of subsurface drip irrigation has progressed from being a novelty used only in experimental fields to an accepted method of irrigation for both tree and vegetable crops (Lamm and Camp, 2007). Subsurface drip irrigation on lettuce (Thompson and Doerge, 1995), tomato, sweet corn (Z. mays), and cantaloupe (Ayars et al, 1999) has significantly increased yield and WUE in all these crops. Subsurface drip irrigation may increase WUE in semiarid environment under saline conditions by increasing yield (Ayars et al, 1999).…”

Fertility Management of Drip-irrigated Vegetables

“…Application of N and K in excess of crop requirements can have significant adverse consequences in addition to the added fertilizer expense. Nitrate contamination of groundwater has become a serious environmental issue in some areas, and excessive fertigation increases NO 3 -N leaching loss (Pier and Doerge, 1995;Thompson and Doerge, 1995). Heavy N application, particularly when NH 4 -N predominates, can induce blossomend rot in crops like tomato and pepper and stimulate vegetative growth at the expense of fruit yield.…”