Capítulo 4. Resultados y análisis de investigación
4.4 Resultados implementación Segundo ciclo
4.4.5 Conclusiones grupales segundo ciclo.
Unlike the results presented earlier representing the above ground properties, the results presented below for the adventitious roots properties are from the analysis of the data of 10 replications out of 12, as two replications were used for the visual evaluation of the soil structure used in this experiment.
3.3.3.1 Total length of roots (greater than 1 mm in diameter)
The results of data analysis in Table 3.5 shows that soil type significantly (p < 0.001) affected the total length of roots (greater than 1 mm in diameter). The total length of plants grown in sandy loam soil was 46.9% greater compared to the total length of the roots of plant grown in clay loam soil. The total length of the roots (greater than 1 mm in diameter) was significantly influenced by soil bulk density (p < 0.001). The total length of the roots in 1.3 Mg m-3 bulk density treatments surpassed the total length of the roots grown in both low and high bulk density treatments by 41.3% and 35.7%, respectively. However, the difference between high bulk density treatments and low density treatments was not significant. The greatest total length of the roots (261.1 mm) was recorded for plants grown in the moderate density sandy loam soil, which was 67.1% greater than the total length of the roots of plants grown in the low density and high density clay loam soil.
3.3.3.2 Root plate diameter
Root plate diameter was not statistically affected by soil type; the mean value of the root plate diameter in clay loam soil was only by 1.5% greater than in sandy loam soil. Plants grown in moderate bulk density soils had a significantly (p < 0.05) greater average root plate diameter than plants grown in low bulk density, being 14.5 % larger. Plants grown in moderate bulk density soil had root systems 10.8% greater on average than those in high bulk density soils, but the difference was not significant.
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Plants grown in sandy loam soil with moderate bulk density showed the greatest root plate diameter and were significantly (p = 0.002) greater than those grown in low bulk density sandy loam soil by 26.3% and not significantly greater from the rest of the treatments.3.3.3.3 Number of roots (greater than 1 mm in diameter)
The impact of soil type on the number of roots (greater than 1 mm in diameter) was highly significant (p < 0.001). The number of roots (greater than 1 mm in diameter) of plants grown in sandy loam soil was 58.2% higher than the number of the roots (greater than 1 mm in diameter) of plants grown in clay loam soil.
The results of data analysis indicates that the number of the roots (greater than 1 mm in diameter) was significantly influenced by soil bulk density (p = 0.004). The moderate bulk density treatments resulted in the highest number of roots (11.1) which was significantly greater than the number of the roots in the low and high bulk density treatments by 26.1% and 29.7%, respectively. Despite the significant effects of soil type and soil bulk density on the number of the roots (greater than 1 mm in diameter), the effect of the interaction of these two factors was statistically non significant, because of the similar pattern of the trend followed in sandy loam soil and clay loam soil with increasing soil bulk density (Figure 3.18).
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Figure 3.18. The effect of soil type and bulk density on the number of the roots (greater than 1 mm in diameter), (S.E.M.) = 1.016, degree of freedom (d.f.) = 45,p = 0.277, n = 10 for each treatment.
3.3.3.4 Angle of spread of the roots
The angle of spread of the roots in sandy loam soil was greater than the angle of spread of the roots in clay loam soil by an average of 25.2% (Table 3.5). Moreover, the greatest angle of spread of the roots recorded at the moderate bulk density treatments was 22.5% greater compared to the angle of spread of the roots in the high bulk density treatments and non-significantly by 13.9% compared to the low bulk density treatments.
The angle of spread of the roots of plants grown in moderate bulk density sandy loam recorded the biggest angle (81.3°) which was significantly greater (p = 0.008) from the rest of the treatments, except the angle of the roots of plants grown in high bulk density sandy loam soil (Table 3.5). The angle of spread of roots of plants grown in high bulk density clay loam soil had the lowest angle of spread of the roots and was significantly lower by 31.3%, 49.5% and 37.5% from the angle of spread
b c b a a a 0 2 4 6 8 10 12 14 16 18 1.1 1.3 1.5 N um ber of t he root s great er than 1 m m /pl an t (i n di am et er) bulk density (Mg m-3) Sandy loam Clay loam
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of the roots of plants grown in low, moderate and high bulk density sandy loam, respectively.3.3.3.5 Number of roots (diameter between 0.5 - 1 mm)
Soil type had no statistical effect (p = 0.969) on the number of roots (diameter between 0.5 - 1 mm). However, the data analysis in Table 3.5 revealed that, soil bulk density significantly affected the number of roots (diameter between 0.5 - 1 mm). Moderate bulk density treatments yielded the greatest average number of roots (diameter between 0.5 - 1 mm) which was 23.1% and 37.2% greater compared to the number of the roots in high and low density treatments, respectively. The lowest number of roots (diameter between 0.5 - 1 mm) of the plants grown in low bulk density sandy loam soil was 53.9% lower than the number of the roots (diameter between 0.5 - 1 mm) of the plants grown in moderate bulk density sandy loam, which recorded the highest number of roots (108.5) among the treatments. Moreover, the number of the roots (diameter between 0.5 - 1 mm) in sandy loam moderate bulk density was 22.7% and 38.5% significantly higher compared to the low and high bulk density clay loam soil, respectively.
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Table 3.5. The effect of soil type and bulk density on the adventitious root properties of winter wheatSandy Loam Clay loam S.E.M. at (d.f. = 45) p value
1.07* 1.3 1.5 1.13 1.3 1.5 Soil
type
Bulk
density Interaction Soil type
Bulk
density Interaction Total length of roots/plant
(greater than 1 mm in diameter) (mm)
144.0 261.1 165.9 85.9 131.0 85.9 11.97 14.66 2.07 ˂ 0.001 ˂0.001 0.216 Root plate diameter/plant
(mm) 43.7 a** 59.3b 55.9b 56.0b 57.4b 48.1ab 1.54 1.89 2.67 0.693 0.007 0.002 Number of roots/plant (greater than 1 mm in diameter) 11.4 15.8 11.1 5.1 6.5 4.5 0.58 0.71 1.01 ˂ 0.001 0.004 0.277
Angle of the spread of the
roots/plant (°) 59.7 b 81.3c 65.6bc 59.1b 56.4ab 41.0a 2.44 2.99 4.22 ˂ 0.001 0.002 0.008 Number of roots/plant (diameter between 0.5 - 1 mm) 50.0a 108.5d 97.3cd 83.8bc 104.8cd 66.7ab 3.01 3.69 5.21 0.969 ˂ 0.001 ˂ 0.001 *Soil bulk density (Mg m-3), ** Values in a row followed by the same letter are not significantly different at p ˂ 0.05 as determined by Tukey test, S.E.M. represents standard error of means, d.f. represents degree of freedom, n = 10 for each treatment.