CHAPTER 4: Field performance of bambara groundnut landraces under irrigated and
5.3 Results
4.3.3 Growth and development
Figure 4. 4: The effect of seed coat colour and landraces on plant growth under (A) irrigated and (B) rainfed field conditions. NB: RF=rainfed, IRRI= irrigated, J= Jozini provenance, T= Tugela Ferry provenance, B=brown colour, LB=light brown colour, R=red colour.
0 20 40 60 80 100 120 140
Plant height (mm) IRRI JB
IRRI JLB IRRI JR IRRI TB IRRI TLB IRRI TR A
0 20 40 60 80 100 120 140
4 5 6 7 8 9
Plant height (mm)
Weeks after planting
RF JB RF JLB RF JR RF TB RF TLB RF TR B
SED (WAP)(P=0.05)=2.2 SED (treatment)(P=0.05)=1.3 SED (seed colour& provenance)(P=0.05)=2.2
99 Measurement of plant height and leaf number started 4 weeks after planting (WAP) when plants had fully established. There were highly significant differences (P<0.001) between water treatments, landraces as well time (WAP), with respect to plant height (Figure 4.4).
Although plants had been receiving equal amounts of irrigation during establishment, results showed that, on average, at 4 WAP plant height was higher under irrigated conditions compared with rainfed (Figure 4.4). At 4 WAP, the Tugela Ferry red landrace selection had the highest plant height (99 mm) followed by Jozini red (92 mm), Tugela Ferry brown (88 mm), Jozini brown (85 mm), Tugela Ferry light brown (81 mm) and Jozini light-brown (75 mm) landrace selections, respectively. A similar trend was observed under rainfed conditions during the corresponding period. At 6 WAP, plant height under irrigated conditions started to decrease while plants under rainfed conditions continued to grow (Figure 4.4). By 9 WAP, plant height was higher under rainfed compared with irrigated conditions (Figure 4.4). Under irrigated conditions, the Tugela Ferry red landrace selection had the highest plant height (84 mm) followed by Jozini red (78 mm), Jozini brown (76 mm), Jozini light brown (73 mm), Tugela Ferry light brown (62mm) and Tugela Ferry brown (53 mm) landrace selections, respectively. Under rainfed conditions, the trend was such that Tugela Ferry red (118 mm) > Tugela Ferry brown (117 mm) > Jozini red (113 mm) > Jozini brown (104 mm) > Tugela Ferry light-brown (104 mm) > Jozini light- brown (100 mm) landrace selections, respectively. Over-all, plant height decreased significantly under irrigated conditions relative to rainfed conditions. A comparison of landrace provenances showed that, based on mean values, the Tugela Ferry provenance generally performed better than the Jozini provenance with regards to plant height. For both provenances and under both irrigated and rainfed conditions, the red landrace selections had taller plants relative to the brown and light-brown selections.
100 Figure 4. 5: The effect of seed coat colour and landraces on plant growth under irrigation and rainfed. NB: RF=rainfed, IRRI= irrigated, J= Jozini provenance, T= Tugela Ferry provenance, B=brown colour, LB=light brown colour, R=red colour.
0 5 10 15 20 25
Leaf number
IRRI JB IRRI JLB IRRI JR IRRI TB IRRI TLB IRRI TR A
0 5 10 15 20 25
4 5 6 7 8 9
Leaf number
Weeks after planting
RF JB RF JLB RF JR RF TB RF TLB RF TR B
SED (WAP)(P=0.05)=0.2 SED (treatment)(P=0.05)= 0.1
SED (seed colour& provenance)(P=0.05)=0.2
101 There were highly significant differences (P<0.001) between treatments, seed colour and days with respect to leaf number (Figure 4.5). By the fourth week, leaf number was the same (4) under both irrigated and rainfed conditions. Similar to this, seed colours, for all provenances, had the same leaf number (4) under both irrigated and rainfed conditions.
Leaf number continued to increase by the 5th week under both water regimes. However, at 6 WAP difference in leaf number started to show between irrigated and rainfed plants.
Under irrigated conditions, leaf number was shown to decrease over time while under rainfed conditions leaf number was shown to increase over time. Under irrigated conditions, at 9 WAP, all landrace selections (brown, light-brown and red) had the same leaf number (3). Under rainfed conditions, during the same period, the Tugela Ferry red landrace selection had the highest leaf number (18) followed by Jozini light-brown (17), Tugela Ferry brown (16), Jozini red (15), Tugela Ferry light brown and Jozini brown (12) landrace selections, respectively. Despite the lower leaf number under irrigated conditions, the red colour selections, for both provenances, had the highest leaf number under both irrigated and rainfed conditions.
102 Figure 4. 6: The effect of seed coat colour and provenances on leaf area index (LAI) under two water treatments, (A) Rainfed and (B) Irrigated. NB: RF=rainfed, IRRI= irrigated, J=
Jozini provenance, T= Tugela Ferry provenance, B=brown colour, LB=light brown colour, R=red colour.
There were highly significant differences (P<0.001) between water regimes, provenances and seed colours with respect to leaf area index (figure 4.6). There were significant differences (P<0.05) in leaf area index over time (Figure 4.6). The trend observed for LAI was similar to observations for leaf number (Figure 4.5). At 4 WAP, LAI was higher under irrigated than rainfed conditions (Figure 4.6). During this period (4 WAP), under irrigated conditions, the Tugela Ferry brown landrace selection had the highest LAI (1.313)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
LAI
JB JLB JR TB TLB TR
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
4 5 6 7
LAI
Weeks After Planting
JB JLB JR TB TLB TR SED(treatment)(P=0.05)= 0.0372
SED(WAP)(P=0.05)= 0.0527
SED(provenance & seed colour)(P=0.05)= 0.0645 A
B
103 followed by Tugela Ferry red (1.066), Jozini brown (1.063), Jozini red (0.870), Jozini light-brown (0.613) and Tugela Ferry light brown (0.580) landrace selections, respectively.
On the other hand, under rainfed conditions, the Tugela Ferry light-brown landrace selection had the highest LAI (0.510) followed by Jozini light-brown (0.397), Tugela Ferry brown (0.393), Jozini red (0.347), Tugela Ferry red? (0.332) and Jozini brown (0.243) landrace selections, respectively. As growth a progress, LAI under irrigated conditions was observed to decline while LAI under rainfed conditions was increasing. The observed decline in LAI corresponded with observations of lower plant height (Figure 4.4) and leaf number (Figure 4.5) observed under irrigated as compared to rainfed conditions.