Short-term impacts of soil nutrient management on maize (Zea mays L.) productivity and weed dynamics along a toposequence in Eastern Zimbabwe

Abstract

Poor soil fertility and weed infestation are among major constraints to maize production in southern Africa. Nutrient and weed management strategies that are products of empirical research, are needed to improve efficiencies on farms. A field experiment was carried out in Eastern Zimbabwe on three smallholder farms positioned on upper, middle and lower catena. The farms differed in soil organic carbon (SOC) content, 3.9, 6.4 and 8.9 g kg À1 (hereafter referred to as low, medium and high), respectively, and are located within one km distance. The objective of the study was to investigate short-term (6 years) repeated application of soil nutrient amendments on maize productivity and weed dynamics across a soil fertility gradient. Treatments included strategic combinations of NPK fertiliser, cattle manure, and lime. On each farm, a randomised complete block design with three replicates was used. Multivariate, Principal Component Analysis, was used to establish the relationship between season, SOC content, nutrient management, and weed density. Maize yield was strongly linked to SOC content, with six-year mean maize grain yields of 1.31, 2.47, and 2.75 Mg ha À1 for low, medium, and high SOC content, respectively. Maize grain yields with cattle manure (CM) or NPK application were only 0.25 and 0.60 Mg ha À1 , respectively for the poorest SOC content field. However, when manure was combined with NPK fertiliser, yields at the site substantially increased to 1.5 Mg ha À1 while in medium and high SOC recorded 2.47 and 2.75 Mg ha À1 respectively. Weed density, and biomass were larger in the medium, and high SOC content. Richardia scabra, Melinis repens, and Cyperus sp. were associated with low SOC. Luecus martinicensis, Bidens pilosa, and Galinsoga parviflora were linked to medium and high SOC content. Results from this study suggest site-specific weed management approach. On soils critically poor in SOC content, maize yield gains are only achieved when organic and mineral fertilisers are combined. Our results also suggest that farmers must increase vigilance and intensity of weed management in soils with medium and high SOC content, particularly after application of CM.

Optimized Fertilization Practices Improved Rhizosphere Soil Chemical and Bacterial Properties and Fresh Waxy Maize Yield

“…In addition, Liu et al [ 36 ] demonstrated that the continuous supply of nitrate had enhanced effects on the development of maize lateral root, and then these changes in root characteristic promoted the absorption of soil nutrients by crops [ 37 ]. Surveys by Cui et al [ 38 ] and Chipomho et al [ 39 ] showed that SOM and total N content in soil had significant correlation with crop productivity in maize fields. This study also showed that fertilization had higher SOM and total N content from V6 to R3 stages, and significantly improved the chemical properties of rhizosphere soil, similar to previous results [ 29 , 40 ].…”

Weed Types and Dynamics Associations with Catena Landscape Positions: Smallholder Farmers’ Knowledge and Perception in Zimbabwe

“…Furthermore, within the landscape position, the use of fertilisers was found to increase weed types. It was found that the use of fertilizers and livestock manure in agroecosystems affects weed species [40,41]. Fertiliser application may not only benefit the crop but to a greater extent weeds because weeds have a fast and efficient nutrient uptake system than crop plants [42].…”

“…However, resource-poor farmers may end up abandoning the crop due to high weed infestation aggressive weed species may dominate the abandoned fields, produce high seed numbers and colonise such farms. Inputs previously committed to failed or abandoned crops are invariably lost when such crops produce no or little economic yield [41].…”

Role of Agroforestry on Farmland Productivity in Semi-arid Farming Regions of Zimbabwe

“…Zimbabwean small-scale farmers rarely apply plant nutrients that are required for crop growth [4] because they do not have money to buy expensive inorganic fertilizers. The most limiting nutrients in the smallholder crop land are nitrogen and phosphorus because the soils are highly leached and acidic [6] . Inadequate nutrient supply and nutrient mining in the communal cropping land has caused high levels of soil degradation in many Zimbabwean soils [7] .…”

“…Agroforestry involves the intentional growing of perennial woody-trees species together with crops. The woodytrees species are incorporated to promote either the biological functions or increase the economic return of the farm, or both [6] . A healthy agro-ecosystem should be beneficial to humans through provision of goods and services at various scales of production [18] .…”