Search

Earthworms are a major component of soil fauna communities with positive effects on soil chemical, biological and physical processes. A study was carried out to investigate the medium-term effects of cultural practices on earthworm communities in an agricultural field. Data were collected in the 2018/2019 cropping season from a six-year-old experiment with tillage system, fertiliser application rate and weeding intensity as the main, sub- and sub-subplots, respectively. Lumbricus (34.4%) and Diplocardia (38.3%) were the dominant genera, while endogeic earthworms (48.4%) dominated the community structure among other earthworm functional groups. Clean weeded plots under the basin planting system had higher Lumbricus abundance (quadruple), genus richness (76.4%) and Shannon diversity index (56.0%) than all other treatments. Inorganic fertiliser application in the conventional tillage system reduced Eisenia abundance and genus evenness by 100.0% and 73.3%, respectively. These results suggest that in minimum tillage systems, frequent hand weeding confers positive effects on earthworms including increased abundance. In conventional tillage systems, application of high doses of inorganic fertiliser is detrimental to earthworm communities. Further studies need to focus on identifying the most sustainable and cost-effective hand weeding frequency for enhanced earthworm diversity and increased crop productivity. [ABSTRACT FROM AUTHOR]

Integrating forage legumes with maize has the potential to restore soil fertility and increase grain yield among smallholder farming systems. A study was conducted over two cropping seasons to determine the effect of intercropping maize with forage legumes on soil fertility restoration, weed biomass and maize yield. Treatments involved: four cropping systems (sole maize, maize-velvet bean, maize-silverleaf, maize-cowpeas) and four fertiliser regimes (no fertiliser, 150 kg ha−1 of compound D fertiliser (7% N: 14% P2O5: 7% K2O) + 150 kg ha−1 ammonium nitrate (34.5% N), 100 kg ha−1 single super phosphate (SSP, 17.5% P2O5) and 200 kg ha−1 SSP). Maize-velvet bean intercropping reduced weed biomass by 80% relative to sole maize and maize-silverleaf intercropping. Maize-cowpea and maize-velvet bean intercropping reduced maize grain yield by 25.9% and 64.7%, respectively, compared to sole maize and maize-silverleaf intercropping. In 2017/2018, maize-silverleaf intercropping increased resin-extractable P2O5 by 60.1% compared to other cropping systems while the three fertiliser treatments increased the levels of this nutrient by 41.9–100%. The results of this study show that intercropping maize with silverleaf has the potential to restore soil fertility and control weeds, without reducing maize grain yield. [ABSTRACT FROM AUTHOR]

Surface-dwelling beetles are among some beneficial arthropods inhabiting agricultural fields, but they can be negatively affected by agricultural practices. In this study, we investigated the effects of plant residue application rates and weeding intensity on surface-dwelling beetle communities and maize yield under two tillage systems, using a long-term experiment at Chinhoyi University of Technology experimental farm, northern Zimbabwe. The experiment was established in December 2012 as a split-split plot in randomized complete blocks replicated three times, and data for our study were collected during two growing seasons (2013/14 and 2014/15). Beetle species such as Abacetus spp., Ancophthalmus oncotipes and Renatiella reticulata showed increased while Dromica limpompoipana had decreased abundances under no- relative to conventional tillage. Abundances of Zophosis boei decreased while those of Gonocephalum simplex , R. reticulata , Stenethmus tentyriniformis and Trachynotus reticulatus increased under plant residue application. During the third growing season of annual runs of the treatments, maize yield was least (4620 kg ha−1) in plots without plant residues and highest (10,978 kg ha−1) in plots treated with 8 t ha−1 of plant residues. During the same growing season, maize grain yield was positively correlated with total abundance of beetles and those of R. reticulata , S. tentyriniformis and T. reticulatus. The effect of tillage system and weeding intensity on beetle abundance and maize grain yield under the environmental conditions of this specific study was minimal, but plant residue application promoted beetle species abundance while increasing maize grain yield. • Plant residue application was the strongest factor affecting beetle community composition • Plant residues increased beetle abundance and maize grain yield • Beetles sampled during the cool season beetles were important regulators of maize yield • Tillage and weeding had some effect on beetle communities [ABSTRACT FROM AUTHOR]

Abstract Soil dwelling beetles contribute greatly to biodiversity and offer important services in agroecosystems including predation, weed herbivory and decomposition. An experiment was conducted in the 2013/2014 and 2014/2015 cropping seasons at Chinhoyi University of Technology experiment station, Zimbabwe, to investigate the impact of tillage system (conservation tillage and conventional tillage), fertilizer application rate and weeding intensity on beetle communities in maize. The experiment was laid out in a split-split plot using a randomized complete block design and replicated three times. Beetles were sampled using un-baited pitfall traps. A total of 6020 beetles were collected comprising 53 species, nine families and four functional groups. Tillage system had the strongest effects on beetle diversity. Advanced constrained analysis using principal response curves revealed that the abundances of Anchophthalmus oncotipes decreased under conservation tillage. In contrast, abundances of Zophosis boei , Gonocephalum simplex , Renatiella reticulata and Stenethmus tentyriniformis increased under conservation tillage relative to conventiona tillage (CT). Detritivore abundances were 50.8% and 45% greater under rip line seeding than CT during the hot dry season of 2014 and cold dry season of 2015, respectively. Predator abundances were almost double in basin planting relative to CT during the cold dry season of 2014 and hot humid season of 2015. In the 2014/2015 cropping season, maize grain yield significantly increased (P < 0.05) from 4963 kg ha−1 in CT to 7848 kg ha−1 in basin planting tillage. Application of a high rate of fertilizer increased maize grain yield by 31.2% compared to the low and medium fertilizer application rates. Weeding twice resulted in the highest maize grain yield but there was no yield benefit in increasing weeding intensity more than twice per season. Our results suggest that there is potential for increasing density and diversity of beneficial beetle species through conservation tillage with crop residue retention. [ABSTRACT FROM AUTHOR]

Highlights • Tillage and mulching were the strongest factors affecting spider community composition. • Lycosidae, Gnaphosidae and Salticidae were high under minimum tillage. • Gnaphosidae and Thomisidae were highest in plots treated with the lowest mulching level. • Fertilizer and weeding treatments had no effect on abundance and diversity. • Minimum tillage increased diversity and richness but did not affect evenness. Abstract Most spiders are generalist predators and important biological control agents of various insect pests of agricultural crops. A study was conducted to determine the impact of cultural practices on the abundnace and diversity of soil surface-dwelling spiders (Araneae). Two experiments were conducted at the Chinhoyi University of Technology experimental farm, Zimbabwe, over the 2013/2014 and 2014/2015 cropping seasons. The two experiments were conducted using a split-split-plot design arranged in randomized complete blocks using tillage, mulching, fertilizer and weeding management as factors, with spider diversity being a response variable. Tillage and mulching had strong effects on spider composition. In the first experiment that involved tillage system as the main plot factor, conventional tillage had a negative effect on ground dwelling taxa as evidenced by high negative taxon weights of Lycosidae, Gnaphosidae and Salticidae. In the second experiment, mulching had strong positive effects on ground dwelling spiders with the strongest being Lycosidae followed Gnaphosidae and Thomisidae. The no-tillage option increased richness by 14.5% compared to conventional tillage. The effective number of species was higher in the no-tillage option (exp^Hʹ = 2.2) than in conventional tillage (exp^Hʹ = 1.8). Our results suggest that no-tillage and retention of plant residue on the soil surface facilitate the abundance of ground and plant wandering spiders. More research is required to assess the specific benefits associated with this increased abundance, such as biological pest control. [ABSTRACT FROM AUTHOR]

field study was carried out with the potato (Solanum tuberosum L.) variety BP1 to determine the influence of plant population density and seed tuber size on the crop's physiological growth components and yield performance under optimal field conditions. Two factors considered were seed tuber size and population density. The first factor involved four seed sizes; S1 (small), 200-350 mm in diameter; S2 (medium), 350-450 mm in diameter; S3 (large), 450-550 mm in diameter and S4 (very large), greater than 550 mm in diameter. The second factor was population density (E) and it was at three levels; level 1 (E1) at 90 by 15 cm, level 2 (E2) at 90 by 30 cm, level 3 (E3) at 90 by 45 cm spacing. Parameters measured included shoot emergence (germination), haulm growth and yield. There were significant differences in mean percentage germination at 9, 10, 11 and 12 days after planting across the four seed sizes. Plants from larger seed potato tubers exhibited greater physiological growth and yield (kg/ha) compared to smaller seed tubers when the experiment was terminated at 95 days after emergence. Large and very large seed potato tubers exhibited greater overall resource use efficiency of allocation of metabolites as measured by growth components and yield at all plant density levels compared to small and medium sized seed tubers. This had implications on the duration of the bulking, physiological growth and consequently on yields obtained at harvest. At the same time, plant population density had no significant (p>0.05) effect on the number of days to emergence. From the results obtained in this study, it can be concluded that the optimum plant population density for good yield was 90 by 30 cm and that large and very large seed sets gave the best yield. [ABSTRACT FROM AUTHOR]

Droughts, short growing seasons and poorly distributed rainfall are major constraints to maize production in eastern semi-arid region of Rwanda. In situ rain water harvesting offers an alternative option to reduce rainwater runoff, increase infiltration and storage of water in soil and reduce the effects of drought streβ on maize grain yield. The objective of the study was to aβeβ the effects of in situ water harvesting techniques on soil moisture content, maize growth and grain yield in Nyagatare, Rwanda in the 2011-2012 seasons. The study comprised of four treatments: pot holing, tied-ridging and mulching compared to control treatment of planting on the flat. The experimental design was randomized complete block with three replicates. Soil moisture content and maize plant dry weight were measured at 8, 11 and 14 weeks after emergence (WAE). There was a significant increase (P<0.001) in soil moisture content and maize plant dry weight from planting on the flat (control), pot hole, tied ridges to mulching at 8, 11 and 14 WAE. Yield components (ear maβ, number of grains per ear and 100 grain weight) and grain yield significantly increased (P<0.001) from planting on the flat, pot holes, tied ridges and were highest in the mulched treatment. Maize grain yield increased(P<0.001) by 49.6, 103 and 136% of the maize grain yield harvested from the flat planting(1593.36 kg ha-1) in the pot-holing, tied ridging and mulching treatments, respectively. The results of this study indicate that mulching, tied ridges and pot holes, in decreasing order of effectiveneβ, have potential to increase soil moisture content and reduce the damage caused by drought streβ to maize growth and grain yield and therefore recommended for farmers in Nyagatare and other drought prone regions. © 2014 Friends Science Publishers [ABSTRACT FROM AUTHOR]