Effects of water and nitrogen treatments on the yield of Isatis indigotica
As shown in Table 3, in the two-year experiment, both the water input and the nitrogen application rate had significant effects on the yield of Isatis indigotica.
As shown in Fig. 4, with increasing water and nitrogen, the yield first increased and then decreased. The interaction between the water input and the nitrogen application rate reached a significant level (P < 0.05). The yield of the W2N2 treatment was the highest, with a value of 7137–7417 kg/ha, followed by that of the W2N3 treatment, with a value of 6679–6962 kg/ha, and the yield of the W3N1 treatment was the lowest, with a value of 5688–6413 kg/ha. The yield of Isatis indigotica in the W2N2 treatment increased by 13.7–21.2% compared with that in the W3N3 treatment (P < 0.05).
The effects of the different treatments on the yield of Isatis indigotica. The values shown are the mean ± SD, n = 3. Asterisks indicate a significant difference at the P ≤ 0.05 level.
At the same irrigation level, the yield performance was N2 > N3 > N1. At the levels of W1, W2, and W3, the yield of the N2 treatment increased by 5.3–7.9%, 6.5–6.9%, and 5.0–9.0% compared with those of the N3 treatment, respectively, and the yield of the N3 treatment increased by 1.4–1.9%, 1.5%-4.5%, and 1.7–3.5% compared with those of the N1 treatment, respectively. At the same nitrogen application level, the yield performance was W2 > W1 > W3. At the levels of N1, N2, and N3, the yield of the W2 treatment increased by 6.9–12.4%, 8.3–11.3%, and 6.8–13.5% compared with those of the W3 treatment, respectively, and the yield of the W3 treatment decreased by 1.6–3.9%, 1.5–1.6%, and 1.3–2.4% compared with those of the W1 treatment, respectively.
Effects of the water and nitrogen treatments on the quality of Isatis indigotica
As shown in Table 4, in the two-year experiment, the water input and nitrogen application rate had significant impacts on the contents of indigo, indirubin, (R,S)-epigoitrin and polysaccharide in Isatis indigotica.
As shown in Fig. 5, The impacts decreased with increasing irrigation amount and nitrogen application rate. Compared with those in the W3N3 treatment, the contents of indigo, indirubin, (R,S)-epigoitrin and polysaccharide in the W2N2 treatment increased by 4.5–5.9%, 2.7–3.1%, 5.2–6.0% and 1.8–2.1%, respectively. At the same irrigation level, the contents of indigo, indirubin, (R,S)-epigoitrin and polysaccharides all decreased in the order N1 > N2 > N3. At the W2 level, the contents of indigo, indirubin, (R,S)-epigoitrin and polysaccharide in the N1 treatment increased by 0.5–1.7%, 0.8–0.9%, 0.8–1.1% and 0.1–0.4%, respectively, compared with those in the N2 treatment. Compared with those in the N3 treatment, the contents of indigo, indirubin, (R,S)-epigoitrin and polysaccharide in the N2 treatment increased by 1.9–2.1%, 1.5–2.2%, 2.1–2.2% and 0.6–1.1%, respectively.
The effects of the different treatments on the quality index of Isatis indigotica. The values shown are the mean ± SD, n = 3. Asterisks indicate a significant difference at the P ≤ 0.05 level.
At the same nitrogen level, the contents of indigo, indirubin, (R,S)-epigoitrin and polysaccharides all decreased in the order W1 > W2 > W3. At the N2 level, the contents of indigo, indirubin, (R,S)-epigoitrin and polysaccharides in the W1 treatment increased by 1.5–2.0%, 1.8–2.1%, 3.0–3.1% and 0.4–0.9% compared with those in the W2 treatment, respectively. Compared with those in the W3 treatment, the contents of indigo, indirubin, (R,S)-epigoitrin and polysaccharides of the W2 treatment increased by 2.3–3.5%, 1.8–2.3%, 2.0–4.0% and 1.0–1.4%, respectively.
Effects of the water and nitrogen treatments on the WUE of Isatis indigotica
As shown in Table 5, in the two-year experiment, the water input and nitrogen application rate had significant impacts on the WUE of Isatis indigotica (P < 0.05).
As shown in Fig. 6, WUE decreased with increasing irrigation amount. The WUE first increased and then decreased with increasing nitrogen application rate. The WUE of the W1N2 treatment was the highest, with a value of 1.95–2.21 kg/m3, followed by the WUE of the W2N2 treatment, with a value of 1.90–2.02 kg/m3. The WUE of the W3N1 treatment was the lowest, with a value of 1.28–1.46 kg/ m3. The WUE of the W1N2 treatment increased by 7.8–8.1% compared with that of the W2N2 treatment, and the WUE of the W2N2 treatment increased by 24.3–27.2% compared with that of the W3N3 treatment.
The effects of the different treatments on the WUE of Isatis indigotica. The values shown are the mean ± SD, n = 3. Asterisks indicate a significant difference at the P ≤ 0.05 level.
At the same irrigation level, the WUE performance was N2 > N3 > N1. At the W1, W2, and W3 levels, the WUE of the N2 treatment increased by 6.5–8.6%, 7.8–8.1%, and 7.4–10.4% compared with that of the N3 treatment, respectively, and the WUE of the N3 treatment increased by 2.9–3.1%, 3.9–6.0%, and 4.5–5.3% compared with that of the N1 treatment, respectively. Under the same nitrogen application rate level, the WUE performance was W1 > W2 > W3. At the N1, N2, and N3 levels, the WUE of the W1 treatment increased by 5.0–11.7%, 2.8–9.2%, and 2.0–10.9% compared with that of the W2 treatment, respectively, and the WUE of the W2 treatment increased by 24.2–29.5%, 24.3 -27.2%, and 23.5–30.3% compared with that of the W3 treatment, respectively.
Effects of water and nitrogen treatments on NUE of Isatis indigotica
As shown in Table 6, in the two-year experiment, the water input and nitrogen application rate had significant impacts on the nitrogen fertilizer use efficiency (NUE) of Isatis indigotica (P < 0.05).
As shown in Fig. 7, With the increase in irrigation amount, NUE increased first and then decreased. With the increase in the nitrogen application rate, NUE decreased gradually. The NUE of the W2N1 treatment was the highest, reaching 33.1–38.1%, followed by those of the W3N1, W1N2, W1N1 and W2N2 treatments, which were in the range of 20.0–35.9%. The differences in NUE among these treatments were not significant. The NUE of the W3N1 treatment was the lowest, at 20.1–22.7%. Compared with that of the W2N2 treatment, the NUE of the W2N1 treatment increased by 9.6–13.0%, and the NUE of the W2N2 treatment increased by 31.8–34.5% compared with that of the W3N3 treatment.
The effects of the different treatments on the NUE of Isatis indigotica. The values shown are the mean ± SD, n = 3. Asterisks indicate a significant difference at the P ≤ 0.05 level.
At the same irrigation level, the NUE performance was N1 > N2 > N3. At the levels of W1, W2, and W3, the NUE of the N1 treatment increased by 9.9–11.8%, 9.6–13.0%, and 6.3–11.6% compared with that of the N2 treatment, respectively, and the NUE of the N2 treatment increased by 31.0–37.6%, 28.8–29.2%, and 28.3–28.6% compared with that of the N3 treatment, respectively. At the same nitrogen application level, the NUE performance was W2 > W3 > W1. At the N1, N2, and N3 levels, the NUE of the W2 treatment increased by 5.7–6.1%, 2.5–4.8%, and 2.3–4.1% compared with that of the W3 treatment, respectively, and the NUE of the W3 treatment decreased by 3.4–8.0%, 6.9–8.2%, and 10.5–14.5% compared with that of the W1 treatment, respectively.
Ethical guideline
The authors confirm that relevant ethical guidelines were followed for plant usage.
Land permit statement
The experimental land belongs to the Yimin Irrigation Experimental Station, in Minle County, Gansu Province, China.
Source: Ecology - nature.com
