Enhancing rangeland productivity through integrated Management of Kongwa weed (astripomoea hyoscyamoides vatke Verdc.): a case study of Kongwa ranch

Abstract

Introduction Kongwa weed (Astripomoea hyoscyamoides Vatke Verdc.) is noxious weed species in Tanzania which is defined as an unusual species that pose harmful effect to other species and ecosystems hence causing significant economic damage in grassland and cropland as well as natural areas. Recently, there is a decline of livestock production due to insufficient animal feeds resulting from diminishing of pasture in range land caused by weeds infestation. This study aimed to develop integrated management strategies and technologies for management of Kongwa weed so as to increase livestock production by improving the natural pasture in grazing land. Specifically, the study sought: (1) To determine efficacy of selected plant species for allelopathic effects against Kongwa weed, (2) To evaluate the effectiveness of selected cultural, biological and chemical methods singly or in combination as management options against Kongwa weed and (3) To establish the most economical integrated weed management option(s) for controlling the Kongwa weed. The first chapter contains general introduction, the second, third and fourth chapter in the dissertation comprise manuscripts in the form of publishable papers which cover the first, second and third specific objectives while chapter five covers general conclusion and recommendation. Methods With respect to specific objective 1, the study was conducted in a screen house in two phases. The experiment was laid out in factorial experiment; the pots were 2 arranged in a randomized complete block design with 12 treatment combinations replicated four times. Factor A contained three types of plant extracts (M. azedarach, R. communis and N. tabacum) and factor B contained four concentration levels (0.0, 2.5, 5.0 and 10 g l-1). Data were collected for plant growth parameters14 to 60 days after sowing in seven days intervals. Data was analyzed using GenStat software (version 16). Turkey's significant test at 5% level of significance. The study was conducted in two sites located in Sejeli ward, Kongwa district. Site A and B contained five and 12 treatments as weed management options applied in paddocks occupied with Cenchrus ciliaris and Cynodon dactylon, respectively. The experimental layout in site A and B followed a randomized complete block design with four replications. Data were collected for plant growth parameters 7 to 35 days after treatment application at seven days interval. Data was analyzed using GenStat software (version 16). Turkey's significant test at 5% level of significance. The economic analysis of natural pasture production and weed management package were carried out based on benefit cost ratio using partial budget analysis per objective 3. The variable costs for purchasing inputs, acquiring of plant materials and labour cost calculated by working out expenditure using prevailing price on different aspects of weed management and gross income under different treatments. The net return and cost-benefit ratio were also calculated to determine the feasibility of the treatments. Data collected from two sites were used to estimate the profitability of pasture yield under different weed management options. The return produced from each treatment was found by multiplying the pasture yield by the market price. 3 Findings Results revealed that, the allelopathic effect of M. azedarach, R. communis at 10 g l- 1concentration showed significant effect at (P≤0.05) on weed height, girth, leaves, leaf area and chlorophyll contents in phase I and II. Significant effect at (P≤0.05) were recorded for treatments applied at concentration level of 10 g l-1 followed by 5 g l-1. Similar effects were observed on chlorophyll contents and number of survived weed at the same concentration in phase I and II. Results showed that, at site A treatment M. azedarach significantly affected the number of Kongwa weed survivors (5) and number of weed leaves (7). Similar effect was observed on pasture DM yield of (8.9 ton ha-1) in the same treatments at P<0.001. However results on site B showed that, number of weed leaves (14), height (37.55 cm) and girth (3 mm) were significantly affected at P<0.001 by 2,4-D treatment, while cutting + M. azedarach treatment significantly affected weed survivor (10) at P<0.001 compared to other applied treatments. Further, hand pulling + M. azedratch and cutting + 2, 4-D had significant influence on pasture DM yield of 14.02 ton ha-1 at P<0.001 compared to other treatments. However, the highest profits of controlling Kongwa weed was obtained from M. azedarach (TSh. 435 555.00 ha-1) and 2, 4-D (TSh. 232 053.00 ha- 1) treatments resulted from the mean pasture MD yield of 8.94 t ha-1 and 6.58 respectively. While at site B, the highest net profit were recorded from treatments on hand pulling + M. azedarach TSh.928 328.00 ha-1 followed by cutting + 2, 4-D TSh. 749 577 ha-1), 2, 4-D (TSh.682 949.00 ha-1) and hand pulling + 2, 4-D (TSh. 648 281.00 ha-1) with the average pasture DM yield of 14.02 t ha-1, 14.02 t ha-1, 12.76 t ha-1 and 12.10 t ha-1 table 4.3 and 4.4 respectively. 4 Conclusion The study concludes that M. azedarach is an important plant species in controlling Kongwa weed due to its allelopathic effect and thus it can be used as a bio-herbicidal plant for controlling the weed compared to R. communis and N. tabacum. However, all allelochemicals activities depend on the level of concentration applied. Therefore, appropriate weed control provided a favourable environment for the pasture growth and development. Integrated weed management option was more effective than single treatment when applied in high weed infestation. Where single treatment was applied, lower yield and marginal return was consistently achieved compared to where supplemented by a combination of treatments. Recommendations For sustainable ecosystems, M. azedarach and R. communis should be used as bioherbicides in managing Kongwa weed in rangelands as an alternative to industrial herbicides. Concentration (10 g l-1) of M. azedarach and R. communis should be used in open field particularly grazing lands. Integrated weed management option applied in high weeds infestation and herbicides or plant extracts applied singly in low weeds infested range lands are recommended. The study suggests weeds management practices; cutting + 2, 4-D, Hand pulling + M. azedarach and hand pulling + 2, 4-D to reduce Kongwa weed in grazing lands consequently minimising the cost of production required for forage optimum yield and increased profitability.