Agriculture Reference
In-Depth Information
TABLE 7.10
Shoot Dry Weight of 10 Tropical Cover Crops as Influenced by N and Bradyrhizobial
Inoculants
Shoot Dry Weight (g Plant
−
1
)
Cover Crops
N
0
N
1
N
2
N
3
Average
1. Crotalaria
0.98e
1.36de
1.95g
1.66e
1.48f
2. Smooth crotalaria
2.89bcd
3.05cd
3.84ef
3.56cd
3.33de
3. Showy Crotalaria
3.59bc
2.67cde
5.83d
4.00c
4.02cd
4. Calopo
2.27cde
3.01cd
2.78fg
2.13de
2.55e
5. Pueraria
1.25de
1.17e
1.21g
0.73e
1.09f
6. Pigeon pea
4.64b
4.46c
4.69de
3.56cd
4.33c
7. Lablab
10.89a
9.82b
11.89b
13.73a
11.58a
8. Black velvet bean
9.42a
9.16b
9.33c
13.37a
10.32b
9. Gray velvet bean
9.52a
11.90a
12.90b
12.66a
11.74a
10. Jack bean
9.85a
13.23a
16.73a
8.16b
11.99a
Average
5.53c
5.98bc
7.11a
6.36b
F-test
N rate (N)
**
Cover crops (C)
**
**
N × C
CVN (%)
11.64
CVC (%)
10.89
Source:
Adapted from Fageria, N. K. et al. (In press).
Commun. Soil Sci. Plant Anal
.
**Significant at the 1% probability level. Means in the same column followed by the same letter are not significantly different
at the 5% probability level by Tukey's test. Average values were compared in the same line for significant differences among
N rates. N
0
= 0 mg N kg
−1
; N
1
= 0 mg N kg
−1
+ Bradyrhizobial inoculants; N
2
= 100 mg N kg
−1
+ Bradyrhizobial inoculants;
and N
3
= 200 mg N kg
−1
.
Overall, the maximal shoot dry weight was produced at N
2
treatment (100 mg N kg
−1
+ inoculant).
The increase in the shoot dry weight with the N
2
treatment was 29% compared to control treatment
(N
0
). Variation in the shoot dry weight among tropical legume cover crops has also been reported
by Fageria et al. (2011). Similarly, improvement in the shoot dry weight of annual crops (cereals and
legumes) with the addition of N was associated with an increase in the leaf area with the addition
of N and improvement in the photosynthetic efficiency of plants (Marschner, 1995; Fageria et al.
2011). Engles and Marschner (1995) and Fageria et al. (2006) reported that N greatly influences the
leaf growth, leaf area duration, and photosynthetic rate per unit leaf area to control the production of
carbohydrates and other photosynthetic products (source activity), as well as the number and sizes
of vegetative and reproductive storage organs (sink capacity).
Fageria et al. (2014) also studied the influence of N and rhizobia treatments on the maximum root
length and root dry weight of 10 tropical legumes. The N × cover crops root length interaction was
significant for root length (Table 7.11), indicating that some crop species were highly responsive to
the applied N and Bradyrhizobial inoculants while others were not. In control treatment (N
0
), maxi-
mal root length varied from 22 cm produced by showy crotalaria to 33 cm produced by smooth cro-
talaria, with an average value of 26.17 cm. At N
1
(0 mg N kg
−1
+ Bradyrhizobial inoculants) and N
2
treatment (100 mg N kg
−1
+ Bradyrhizobial inoculants), minimal root length was produced by the
black velvet bean and maximum root length was produced by the pigeon pea. At N
3
(200 mg N kg
−1
)
treatment, the situation changed and the minimal root length of 20 cm was produced by the jack
bean and maximum root length of 33.33 cm was produced by the gray velvet bean. Across four N
