Rocket: a Mediterranean crop for the world - Bioversity International

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46 ROCKET GENETIC RESOURCES NETWORK )JJIGX SJ RMXVSKIR JIVXMPM^EXMSR No yield response occurred in the 1995 trial while in 1996 the yields were slightly higher with 200 kg/ha of nitrogen. This response can be explained by the high soil fertility. In 1996, dry matter was lowered by nitrogen application and stems were heavier and taller (200 kg/ha) than those of the unfertilized plants (Table 2, Fig. 2). There were no statistical differences between nitrogen sources for all the considered parameters. During the 1996 experiments, the weight of leaves per plant was affected by the planting method. In the transplanted crop, it was higher in the nitrogen rates trial and lower in the plant density experiment (Fig. 3). The stems per plant were heavier in the transplanted crop and with 200 kg/ha of nitrogen (Table 2). As always, yields were decreasing from first to last cuttings, and in the 1995 trial a linear trend was observed. In 1995, the fibre content of the unfertilized plants did not show any significant difference among cuttings: on average it was 9.3% in the first two cuttings and 7.6% in the last two. Although wild rocket accumulates a large amount of nitrates – as much as other leafy vegetables such as lettuce, spinach and rocket salad (Ventrella et al. 1993; Santamaria et al. 1995; 1996) – no significant differences were detected between the two nitrogen sources and among the nitrogen rates. On average, nitrate content was 4000 mg/kg of fresh leaf weight. The SO - content (3412 mg/kg ) was higher with ammonium sulphate than with 4 ammonium nitrate (2771 mg/kg). Leaves (g plant -1 ) Leaves (g plant -1 ) 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 B B A 0 100 200 Plant density A N rates (kg ha-1) Pl. method Cuttings B B B S T Nitrogen rates A A B A B 1st 2nd 0 100 200 S T 1st 2nd N rates (kg ha-1) Pl. method Cuttings A B Fig. 3. Effect of plant density, planting method, time of cutting and nitrogen rate on weight of leaves of wild rocket in the two trials (top = 1995; bottom = 1996). Bars with different letters are significantly different at P=0.01 according to SNK.
+)2)8-' 6)7396')7 &6))(-2+ %2( '908-:%8-32 7EPMRI [EXIV IJJIGX Salinity influenced significantly the different parameters taken into account. 7EPMRMX] ERH WIIH KIVQMREXMSR Total germination decreased as salinity increased and varied between 62% for control and 22% for the most stressed treatment (20 dS/m). This decrease was significant compared with the control (ECw >10 dS/m (Fig. 4). The ATG (Fig. 5) seemed to increase with higher salinity with values ranging between 4.5 (ECw=6 dS/m) and 6.2 days (ECw=20 dS/m). Precocity germination values (Fig. 6) showed a steady upward trend (up to ECw=12 dS/m), increasing for ECw >12 dS/m and varying from 3.1 to 3.4, 3.3 to 3.9, 3.6 to 4.9, 3.9 to 6.0, 5.1 to 7.4 days for T , T , T , T , T , respectively, passing 10 25 50 75 90 from the control to the most concentrated solutions. 7EPMRMX] ERH QEVOIXEFPI ]MIPH The increase of salinity caused a strong decrease of marketable yield of wild rocket. The marketable yield ranged between 399 and 130 g/plant, passing from the control to the more stressed treatment (T 6 ) (Fig. 7). The yield reduction, compared with the control, was 10, 40, 49, 62 and 67% from T 2 to T 6 (Fig. 7), respectively. Germinated seeds (%) 70 60 50 40 30 20 10 0 A A B A D A C A D A D B D 0 2 4 6 8 101214161820 ECw (dS/ m) Fig. 4. Germinability of wild rocket seeds trend vs. ECw. Number of days C E D E 8 7.5 7 6.5 6 5.5 5 4.5 4 3.5 3 E F F ATG (days) 0 4 8 12 16 20 ECw (dS/ m) 7 6.5 6 5.5 5 4.5 4 DE E CE E BC BD CE CE CE 0 2 4 6 8 10 12 14 16 18 20 ECw (dS/m) Fig. 5. Average time of germination (ATG) vs. ECw of wild rocket seeds. T10 T25 T50 T75 T90 Fig. 6. Germination precocity trend vs. ECw of wild rocket seeds. B A
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