Yield and nitrogen recovery of lettuce under different irrigation regimes.

Abstract

Studies were conducted to determine the effect of irrigation regime on yield and nitrogen recovery of field grown lettuce in the Bekaa Valley of Lebanon, under non limiting soil N conditions. Within the experimental plots, irrigation differentiation was made upon crop evapotranspiration (ETc) measured on a non-weighing lysimeter of 16 m². The treatments included a control, I-100, irrigated at 100% of ETc, and two water deficit treatments, I-80 and I-60, irrigated at 80% and 60%, of ETc, respectively. Prior to planting, all plots received fertilizers broadcast at a rate of 250 kg ha -1 of NPK-fertilizer (17%). At 6-leaf and 12-leaf stages, ammonium nitrate (34.5%) was applied with irrigation water in two applications of 125 kg ha -1 each. Local groundwater containing 10 mg l -1 N-NO 3 was used for irrigation. Yield was determined in a final destructive harvest. Crop evapotranspiration reached on the lysimeter a total of 433 mm for a total growing period of 70 days. Results showed that water stress caused by the deficit irrigations significantly reduced leaf number, leaf area index and dry matter accumulation (p<0.05). Water deficit also reduced final fresh weight by 20% to 30% with comparison to the control. Nitrogen recovery reached 218 kg N ha -1 at maturity as compared to control, while consistent reductions averaging 35% and 40% were observed on I-80 and I-60, respectively. Nitrogen use efficiency (NUE) also decreased markedly in to the less irrigated treatments. Finally, it could be concluded that nitrogen inputs from groundwater was considerable as a component of the soil nitrogen balance and increased the potential of N loss with leaching as a source of point pollution.

EFFECT OF IRRIGATION LEVELS AND RICE STRAW COMPOST RATES ON YIELD, CHEMICAL COMPOSITION AND WATER USE EFFICIENCY OF CABBAGE (Brassica oleraceae var. Capitata L.)

“…Therefore, the decreasing of nutrients content in cabbage plant at 65% DASM may be due to redacting the solubility of mineral in the soil; hence movement of cations to root is reduced (Frank and Viets, 1967). The same trend was found by Karam et al (2002) who found that the highest nitrogen uptake was observed in lettuce plants of the well-irrigated treatment and it decreased with increasing water stress level. As regard to nitrate accumulation, the results show that there is a general significant negative effect on the nitrate content in inner leaves due to increasing each of available soil water in root zone (Table,5).…”

Root Water Uptake by Romaine Lettuce in a Muck Soil: Linking Tip Burn to Hydric Deficit

“…The results of this study are, therefore, consistent with the literature (Karam et al, 2002; Coelho et al, 2005; Kuslu et al, 2008; Capra et al, 2008; Mansuroğlu et al, 2011; Bozkurt et al, 2009; Bozkurt and Mansuroğlu, 2011) concerning the importance of eliminating root water uptake deficit by managing irrigation to meet 100% of the ET demand. The results are also consistent with the general understanding that Ca‐related physiological disorders are associated with short periods of limited Ca 2+ supply to the plant, which is itself associated with limited water fluxes.…”

The effects of drip line depths and irrigation levels on yield, quality and water use characteristics of lettuce under greenhouse condition

“…The rates of Et were low at the early stages of vegetative growth (from 1 to 15 days after transplanting, DAT), then increased gradually (from 16 to 57 DAT) by the end of the growing season, when crops had reached the maximum number of mature leaves in the experiment. Likewise, Karam et al (2002) and Bozkurt et al (2009) demonstrated similar results in their study. There was a significant polynomial relationship (R 2 =0.96 in TDI, R 2 =0.82 in SDI 10 and R 2 =0.93 in SDI 20 treatments) between the lettuce yield and the crop Et as shown in Figure 2.…”