Effects of foliar fertilization of biostimulants obtained from sewage sludge on olive yield

Figures & data

Table 1. Chemical characteristics and protein molecular weight distribution (mean ± standard error, n = 3) of sewage sludge and the two experimental biostimulants

	SS	BS1	BS2
Organic matter (g kg^−1)	475a ± 19	479a ± 17	473a ± 12
N (g kg^−1)	30.7a ± 3.3	29.4a ± 2.1	29.0a ± 4.2
P (g kg^−1)	14.1a ± 1.9	15.1a ± 2.2	16.3a ± 1.7
K (g kg^−1)	6.4a ± 1.4	6.8a ± 1.0	6.3a ± 1.1
Ca (g kg^−1)	44.3a ± 2.7	44.9a ± 3.9	43.7a ± 2.9
Mg (g kg^−1)	7.5a ± 1.7	7.9a ± 1.4	7.7a ± 1.1
Fe (g kg^−1)	17.5a ± 1.5	16.8a ± 1.9	18.1a ± 1.6
Mn (mg kg^−1)	164a ± 16	162a ± 21	169a ± 18
Cu (mg kg^−1)	298a ± 22	301a ± 19	311a ± 16
Zn (mg kg^−1)	131a ± 17	127a ± 11	124a ± 20
Cd (mg kg^−1)	3.5a ± 1.4	3.1a ± 0.9	3.3a ± 1.9
Ni (mg kg^−1)	12.9a ± 2.7	13.8a ± 1.3	13.4a ± 1.1
Pb (mg kg^−1)	6.3a ± 2.0	6.5a ± 1.7	6.2a ± 2.6
Protein molecular weight distribution (Da)
> 10,000	98.2a ± 1.4	39.9b ± 2.9	34.8c ± 3.6
10,000–5000	0.70a ± 0.12	17.0b ± 3.2	16.9b ± 1.7
5000–1000	1.1a ± 0.2	11.7b ± 2.1	11.6b ± 1.7
1000–300	0.0a ± 0.0	2.7b ± 0.9	3.3b ± 1.1
< 300	0.0a ± 0.0	28.7b ± 2.9	33.4c ± 3.3

Files followed by the same letter(s) are not significantly different according to the Tukey test (p < 0.05).

SS: sewage sludge; BS1: biostimulant 1; BS2: biostimulant 2

Figure 1. Design of the experimental layout.

Table 2. Chemical composition (mean ± standard error, n = 3) of olive tree leaves (on a dry matter basis) for all treatments during the experiment. Columns followed by the different letter(s) are significantly different according to the Tukey test (p < 0.05)

	N^† (g kg^−1)	P (g kg^−1)	K (g kg^−1)	Ca (g kg^−1)	Mg (g kg^−1)	Fe (mg kg^−1)	Cu (mg kg^−1)	Mn (mg kg^−1)	Zn (mg kg^−1)
	2017 year
A0 treatment	9.3a ± 1.1	0.77a ± 0.05	7.1a ± 1.9	4.2a ± 1.2	15.4a± 2.1	308a± 25	4.2a ± 1.2	18.7a ± 2.1	13.5a ± 1.8
A1 treatment	11.2b ± 1.8	0.90b ± 0.09	8.9b ± 1.5	4.8a ± 1.4	18.9b ± 2.4	334b ± 21	4.9a ± 1.2	25.0b ± 2.5	15.3ab ± 1.5
A2 treatment	13.7c ± 1.5	1.1b ± 0.08	9.4b ± 1.2	5.0a ± 1.2	20.6b ± 1.9	345b ± 18	4.9a ± 1.4	29.2b ± 2.2	16.4b ± 1.1
	2018 year
A0 treatment	11.1a ± 1.9	1.1a ± 0.2	8.9a ± 1.2	6.0a± 1.8	21.3a± 2.2	353a± 32	5.8a ± 1.1	26.9b ± 2.7	19.8a ± 1.6
A1 treatment	15.5b ± 2.1	1.7b ± 0.2	11.1b ± 2.0	6.9a ± 1.5	23.9b ± 2.1	386b ± 25	6.5a ± 1.3	31.4c ± 2.4	24.3a ± 1.9
A2 treatment	18.7c ± 2.5	1.9b ± 0.3	12.8b ± 1.9	7.1a ± 1.6	25.4b ± 2.3	441c ± 33	6.7a ± 1.2	33.8c ± 2.9	27.5b ± 1.7
	2019 year
A0 treatment	9.0a ± 0.8	0.80a ± 0.07	7.5a ± 1.4	4.2a ± 1.0	14.9a± 2.4	312a ± 22	4.3a ± 1.0	17.7a ± 1.9	14.8a ± 1.5
A1 treatment	11.4b ± 1.9	0.92ab ± 0.07	9.1b ± 1.3	4.7a ± 1.1	18.7b± 1.9	347b ± 24	5.0a ± 1.3	25.4b ± 2.4	15.7ab ± 1.2
A2 treatment	13.5c ± 1.6	0.99b ± 0.08	9.4b ± 1.1	5.1a ± 1.3	20.0b± 2.0	359b ± 19	5.2a ± 1.3	29.7b ± 2.0	16.7b ± 1.4
	2020 year
A0 treatment	10.8a ± 1.5	1.2a ± 0.2	9.3a ± 1.5	6.2a ± 1.4	22.4a ± 2.5	349a ± 37	5.5a± 1.4	28.3b ± 2.1	20.1a± 1.7
A1 treatment	15.1b ± 1.3	1.9b ± 0.3	11.3b ± 1.7	6.9a ± 1.3	24.1b ± 1.9	382b ± 18	6.4a ± 1.2	32.1c ± 2.7	24.1a ± 1.5
A2 treatment	18.3c ± 1.2	1.9b ± 0.2	12.5b ± 1.4	7.1a ± 1.2	25.3b ± 1.7	445c ± 24	6.6a ± 1.3	34.7c ± 2.2	27.7b ± 1.8

^†Fresh matter

BS1: biostimulant 1; BS2: biostimulant 2

Table 3. Evolution of chlorophylls A and B and carotenoids (mean ± standard error, n = 3) of olive tree leaves (on a dry matter basis) for all treatments during the experiment. Columns followed by the different letter(s) are significantly different according to the Tukey test (p < 0.05)

	Chlorophyll A(mg g^−1)	Chlorophyll B(mg g^−1)	Carotenoids(mg g^−1)
	2017 year
A0 treatment	0.48a ± 0.08	0.19a ± 0.07	8.2a ± 0.5
A1 treatment	0.52ab ± 0.1	0.26ab ± 0.1	9.3b ± 0.8
A2 treatment	0.57b ± 0.2	0.29b ± 0.06	9.6b ± 0.7
	2018 year
A0 treatment	0.51a ± 0.1	0.22a ± 0.07	8.8a ± 0.9
A1 treatment	0.63b ± 0.2	0.30b ± 0.06	10.1b ± 0.4
A2 treatment	0.75c ± 0.2	0.34b ± 0.1	10.9b ± 0.6
	2019 year
A0 treatment	0.46a ± 0.1	0.21a ± 0.09	8.0a ± 0.5
A1 treatment	0.50ab ± 0.3	0.28ab ± 0.07	9.5b ± 0.8
A2 treatment	0.58b ± 0.2	0.30b ± 0.1	9.9b ± 1.0
	2020 year
A0 treatment	0.50a ± 0.2	0.24a ± 0.05	8.6a ± 0.8
A1 treatment	0.62b ± 0.2	0.31ab ± 0.08	10.2b ± 1.0
A2 treatment	0.77c ± 0.3	0.36b ± 0.07a	11.1b ± 1.1

BS1: biostimulant 1; BS2: biostimulant 2

Figure 2. Olive yield during the four experimental seasons (mean ± standard error, n = 3). Columns followed by the different letter(s) are significantly different according to the Tukey test (p < 0.05).