Allelopathic sorghum aqueous root extracts inhibit germination and seedling growth of crops and weeds

Allelopathic sorghum aqueous extracts can be used as sprays against weeds of arable lands. Water-soluble allelochemicals in the aqueous extracts may also negatively affect crops. Root aqueous extracts from the South African landrace sorghum IS9456 and the Botswanan commercial variety Mahube, with high (584.69 μg mg-1 root fresh weight) and low (17.38 μg mg-1 root fresh weight) sorgoleone contents respectively, were tested on germination, radicle length, plumule length and dry weight of goosegrass [Eleusine indica (L.) Gaertn], blackjack [Bidens pilosa (L.)], maize [Zea mays (L.)], soya bean [Glycine max (L.) Merr.] and wheat [Triticum aestivum (L.)]. Factors in five glasshouse experiments were the two sorghum varieties and four root extract solutions (0%, 5%, 10% and 20%) (w/v) arranged in a randomised complete block design with six replications. There was no significant effect (P>0.05) of variety and root aqueous extract on germination, radicle length, plumule length and dry weight of maize and on germination of wheat and goosegrass. The sorghum accession IS9456 significantly (P<0.05) reduced plumule length and dry weight of wheat and goosegrass and germination, plumule length and dry weight of soya bean and blackjack compared to Mahube. Increasing strength of root aqueous extract solution significantly (P<0.001) reduced plumule length and dry weight of wheat and goosegrass as well as germination and dry weight of soya bean and blackjack. Extracts from IS9456 had greater inhibitory effects on crop and weed germination and growth compared to those from Mahube. Due to its low sorgoleone content and weak weed suppression from its root aqueous extracts, Mahube may have low potential for use in allelopathic weed control. The sorghum accession IS9456, which also produces very high sorgoleone content, may be used in integrated weed management exploiting allelopathy from both sorgoleone and water-soluble allelochemicals, although farmers will have to be careful in terms of crop rotations since the aqueous extracts also inhibit germination and growth of some crops. Field studies may be required to further confirm allelopathic effects of root aqueous extracts from IS9456

Allelopathic sorghum aqueous root extracts inhibit germination and seedling growth of crops and weeds

Allelopathic sorghum aqueous extracts can be used as sprays against weeds of arable lands. Water-soluble allelochemicals in the aqueous extracts may also negatively affect crops. Root aqueous extracts from the South African landrace sorghum IS9456 and the Botswanan commercial variety Mahube, with high (584.69 μg mg-1 root fresh weight) and low (17.38 μg mg-1 root fresh weight) sorgoleone contents respectively, were tested on germination, radicle length, plumule length and dry weight of goosegrass [Eleusine indica (L.) Gaertn], blackjack [Bidens pilosa (L.)], maize [Zea mays (L.)], soya bean [Glycine max (L.) Merr.] and wheat [Triticum aestivum (L.)]. Factors in five glasshouse experiments were the two sorghum varieties and four root extract solutions (0%, 5%, 10% and 20%) (w/v) arranged in a randomised complete block design with six replications. There was no significant effect (P>0.05) of variety and root aqueous extract on germination, radicle length, plumule length and dry weight of maize and on germination of wheat and goosegrass. The sorghum accession IS9456 significantly (P<0.05) reduced plumule length and dry weight of wheat and goosegrass and germination, plumule length and dry weight of soya bean and blackjack compared to Mahube. Increasing strength of root aqueous extract solution significantly (P<0.001) reduced plumule length and dry weight of wheat and goosegrass as well as germination and dry weight of soya bean and blackjack. Extracts from IS9456 had greater inhibitory effects on crop and weed germination and growth compared to those from Mahube. Due to its low sorgoleone content and weak weed suppression from its root aqueous extracts, Mahube may have low potential for use in allelopathic weed control. The sorghum accession IS9456, which also produces very high sorgoleone content, may be used in integrated weed management exploiting allelopathy from both sorgoleone and water-soluble allelochemicals, although farmers will have to be careful in terms of crop rotations since the aqueous extracts also inhibit germination and growth of some crops.Field studies may be required to further confirm allelopathic effects of root aqueous extracts from IS9456

The manipulation of irrigation and drying-off schedules of sugar cane to increase sucrose yields

A research paper on the manipulation of irrigation in order to achieve higher sugar-cane yields in Zimbabwe.Perusal of sugar cane production records in the sugar cane belt located in the low-veld of Zimbabwe indicated that sucrose yield was generally lower when water was abundant compared to drought years. It was therefore hypothesized that sucrose yield would be increased by restricting irrigation compared to current practice. Three irrigation treatments, namely, irrigating at crop factor t.00 (current practice), irrigating at crop factor 0.85 and Irrigating at crop factor 0.70, were tested in factorial combination with three drying-off treatments: drying- off to 55 per cent moisture depletion (current practice), to 60 per cent and, to 65 per cent moisture depletion. The experiment was laid out as a split-plot. A standard cane variety NCO 376, which forms 97 per cent of the area under cane was used in the experiment. The results clearly indicated that it is possible to manipulate sucrose concentration and hence sucrose yield by restricting the amount of water applied to the sugar cane crop. Highest sucrose concentration and sucrose yield per hectare was achieved by irrigating at crop factor 0.85 and drying-off to 60 per cent depletion. It is concluded that inducing mild stress by restricting water to levels that do not fall below crop factor 0.85 will increase sucrose yield in the low-veld

Reduced dosages of atrazine and narrow rows can provide adequate weed control in smallholder irrigated maize (Zea mays L.) production in South Africa

An on-farm experiment was conducted in Zanyokwe irrigation scheme to investigate the effects of row spacing (45 and 90 cm) and atrazine dosage (33, 67 and 100% of the label recommended dosage) on weed density and biomass and on maize yield. Overall percent kill of weeds increased with increase in atrazine dosage and with reduction in row spacing. Percent kill varied according to weed species with a 100% kill of broad leaf weeds such as Amaranthus hybridus, Nicandra physaloides and Bidens pilosa regardless of herbicide dosage while Digitaria sanguinalis, Cyperus esculentus, Cynodon dactylon and Oxalis latifolia could not be controlled even at the LRD. Weed density at maize physiological maturity decreased by 11% when row spacing was decreased from 90 to 45 cm. Atrazine dosage and row spacing did not have significant interactive effects and their main effects did not significantly affect weight of green cobs, cob length or grain yield. The study demonstrated the possibility of incorporation of reduced herbicide dosages and narrow rows to achieve adequate weed control and optimise on yields in smallholder farming systems.Key words: Row spacing, reduced atrazine dosages, weed density, weed biomass, maize yield

Impact of participatory research on assessment of farming systems on overall adoption of new cropping technology by smallholder farmers in semi-arid area of Zimbabwe

A research paper on the farming systems of Zimbabwe vis-a-vis the adoption of modern scientific technology to boost yields in rural area small- holder farmlands.Participatory rural appraisal (PRA) techniques were used in Matibi II Communal Area in Natural Region V of Zimbabwe in December 1994 to obtain a sound knowledge of the existing cropping systems and crop production constraints. In these PRA farmers were also asked to rank the value of the crops they grow based on researcher defined, but mutually agreed, criteria relating to agronomy, socio-economic, use and production reliability. Major crops in the area were sorghum, maize and sunflower, grown by 83,92 and 76 percent of the farmers, respectively, and occupied 39, 25 and 20 percent of the land, respectively. Farmers in the area preferred maize for making theirtraditional dish (sadza) and yet realised that sorghum was the most suitable crop for their environment. Farmers realised that sunflower can be grown to generate household income yet its production lagged behind. Major production constraints identified were poor stand establishment, low yields, shortage of household income, seed, draught power, labour, poor and unreliable rainfall, poor infrastructure and market facilities in maize, sorghum and sunlfower. Farmer managed and farmer implemented participatory on-farm trials were conducted in Matibi II communal area of Zimbabwe during 1994/95 season to compare economic performance of sunflower, sorghum and maize; and to compare local and improved sorghum varieties. Farmers’ participation was not easily available until farmers’ initial suspicion was overcame. Involvement of extension agents in all aspects improved rapport and farmer participation in technology testing, adapting and adoption. Evaluation of the technologies by farmers involved focus group discussions (FGD), interviews, farm walks, matrix ranking exercises and field days. Farmers used high seed rates than recommended for sorghum and sunflower - perhaps a reflection of their experiences in obtaining poor crop stands. This impacted negatively on the adoption of improved varieties as adoption implied a high cash outlay in the purchase of seed. Improved sorghum varieties showed yield superiority over traditional landraces. Although maize had the highest variation in grain yield of all the three species it gave farmers the best return per labour hour- reflecting that maize may be agroecoiogically unfit but returns to scarce resources may be attractive. If net income is based on official prices, sunflower seemed to perform betterthan maize and sorghum. During FGD and fields days farmers who participated in this study indicated that they were willing to adopt improved sorghum varieties and were eager to increase area under sunflower in the following seasons. A study conducted after 1995 96 season in Matibi II showed that 40 percent of the sorghum varieties grown by farmers were improved varieties suggesting that farmer participatory approach used in this study was highly effective in allowing farmers to test adapt and adopt new cropping technologies

Participatory variety selection of maize genotypes in the Eastern Cape Province of South Africa

Participatory variety selection (PVS) is important in understanding farmers’ selection criteria, raising awareness, and facilitating adoption of improved varieties. This study aimed to understand farmers’ maize selection criteria, identify superior varieties based on farmers’ selections, combined with use of agronomic yield data. The study was conducted in Jixini and Mkhwezo in the Eastern Cape Province of South Africa. Focus group discussions (FGD) and semi-structured questionnaires were used to identify maize selection criteria. Seven maize open pollinated varieties (OPVs) from CIMMYT-Zimbabwe (ZM 305, ZM 423 ZM 501, ZM 525, Obatanpa, ZM 621, ZM 627), two from IITA-Nigeria (BR 993, and Comp 4), three locally grown maize OPVs (Okavango, Afric 1 and Nelson’s Choice) and a hybrid check (Pan 6479) were evaluated together with farmers in each of the villages. Farmer-selection criteria common to both villages were ear traits such as taste, long cobs, and big kernels. Other traits, such as prolificacy, early maturity, retainability of seed and dark leaves were village specific. Three varieties (Okavango, ZM 305 and ZM 501) were selected by farmers. In addition, there were no significant differences between the highest yielding varieties within each site. Farmers’ choices were, therefore, consistent with selections made based on yield performance. However, some of the important traits for farmers, such as taste, were not normally prioritised, but should be considered when developing or recommending varieties. This will increase the likelihood of their adoption in marginal areas of South Africa.Keywords: Participatory variety selection, selection criteria, farmer, maiz

Reduced atrazine doses combined with sorghum aqueous extracts inhibit emergence and growth of weeds

Combining low doses of herbicides with allelopathic plant extracts subject weeds to different mechanisms of action, which reduces herbicide resistance. The effects of reduced atrazine doses combined with sorghum aqueous extracts (sorgaab) from sorghum accessions IS9456, IS22320 and Mahube on emergence and growth of Bidens pilosa and Eleusine indica were evaluated in a greenhouse experiment at the University of Zimbabwe in 2017. Two experiments were set up as a 3 ˟ 5 factorial arrangement in a completely randomized design testing sorghum varieties as sources of sorgaab, and five atrazine-sorgaab mixtures (100% sorgaab, 10% of the label recommended dosage (LRD) of atrazine for maize + 90% sorgaab, 30% LRD atrazine + 70% sorgaab, 100% LRD atrazine, and untreated check). Percent emergence, height, and total chlorophyll content in leaves significantly decreased (P<0.001) as influenced by sorghum variety in the order IS22320>Mahube>IS9456, for B. pilosa and E. indica. Sorghum variety significantly (P<0.001) affected dry weight of B. pilosa similarly to other parameters but did not significantly (P>0.05) affect dry weight of E. indica. Percent emergence, height, total chlorophyll content and plant dry weight significantly (P<0.001) decreased in the order untreated control>100% sorgaab>10% LRD atrazine + 90% sorgaab>30% LRD atrazine + 70% sorgaab>100% LRD atrazine. There were significant (P<0.05) effects of sorghum variety as source of sorgaab ˟ atrazine-sorgaab mixture interactions on B. pilosa emergence and height and E. indica height. There is potential to exploit sorghum allelopathy using aqueous extracts alone, and in mixture with reduced doses of atrazine in controlling certain weeds. However, the allelopathic efficacy of sorgaab was dependent on sorghum variety. The sorghum variety IS9456 possibly produces high amounts of water soluble allelochemicals, making it a suitable candidate for use in integrated weed management

Agronomic practices, major crops and farmers’ perceptions of the importance of good stand establishment in Musikavanhu Communal Area, Zimbabwe

A journal article on Zimbabwe farmers’ perceptions of the importance of good stand establishment.Surveys were conducted of rain-fed crops growing in farmers’ fields in the Musikavanhu Communal Area in Natural Region V of Zimbabwe during and after the 19S5/96 cropping season. The major crops were sorghum, maize and sunflower grown by 94.36 and 15 per cent of the farmers, respectively, and occupied 82.12 and seven per cent of the land. Eleven sorghum cultivars were grown in the area during the 1995/96 season, although only four were grown by more than 10 per cent of the farmers. The most popular maize variety was grown by 28 per cent of farmers on 10 per cent of the land, but had been distributed as part of a drought relief package. Stand establishment was identified as a major crop production constraint in this area. More than 50 percent of the farmers gap-filled at least once and there was a good correlation (R2 = 0.73) between frequency of re-sowing of sorghum and the number of varieties present in fields because seed of the initial, preferred variety was not available for later sowings. On-farm seed priming was fairly common in maize and transplanting, using thinnings, was almost universal in sorghum