Intercropping agriculture with legume trees is a promising strategy to improve soils with low soil organic matter (SOM) and nitrogen (N) contents, which is a common problem in many Southern African regions. Objective of this research was to explore long-term effects of legume-intercropping on SOM pools and soil fertility. We examined a maize-based cropping system with gliricidia (Gliricidia sepium) as intercropping legume tree on a Ferric Lixisol in Southern Malawi. The experimental trial at Makoka Research Station was in its 29th year of management with leaf biomass incorporated into the soil regularly. We determined concentrations of organic carbon (C) and N, exchangeable cations, and available phosphorus (P) of topsoil samples (0–20 cm). We used density fractionation of SOM to gain fractions that roughly approximate SOM pools with fast turnover (not associated to soil minerals), intermediate turnover (occluded within soil aggregates) and slow turnover (mineral associated SOM). We further determined water dispersible clay (WDC) and pedogenic oxides, as these are often involved in the C-stabilization process in tropical soils. Maize-gliricidia intercropping plots showed higher soil pH-values, and higher concentrations of exchangeable Mg and Ca than plots with maize monoculture. In addition, significantly higher contents of C (17.3 vs. 7.03 g kg−1) and N (1.51 vs. 0.7 g kg−1) were found at intercropping plots indicating a C-sequestration rate of 0.3 g C kg−1 a−1, while monoculture induced the loss of SOM with a rate of −0.1 g C kg−1 a−1. C and N contents doubled in pools with fast and with slow turnover and increased by >300% in SOM pool where C and N is bound in soil aggregates. Concomitantly, WDC was significantly lower in intercropping plots than in monoculture plots. Our data emphasize the fast turnover of SOM in subtropical soils and indicate that SOM in arable soils decreases continuously without suitable C-input strategy. Maize-gliricidia intercropping had positive effects on biomass production and C-input at Makoka Research Station and improved soil fertility. In addition, aggregate formation was enhanced and storage of SOM within aggregates and at mineral surfaces increased. Our results indicate a great potential of maize-gliricidia intercropping for improved C management in subtropical Lixisols. Intensive monitoring seems to be promising to validate and quantify the impacts of this measure.
Tag: plant nutrients
Characterization of soil health and nutrient content status across the North-East Maasai Landscape, Arusha Tanzania
Soil fertility management has been a great challenge to smallholder farmers in the Northern Tanzania, especially in the Maasai landscape. Therefore understanding the nutrient status become important to forecast productivity, promote sustainability, and propose an appropriate technique for crop productivity sustainability. The study examines soil fertility status of the Maasai landscape. Systematic approach known as the Land Degradation Surveillance Framework (LDSF) were used to identify soil sampling points. A total of 604 soil samples from two soil depth (0 – 30 and 30 – 50 cm) were collected for physiochemical properties analysis using Mid-infrared (MIR) spectroscopy. The chosen level for determining statistical significance, was set at P = 0.05. Results showed a significant differences (P < 0.01) for particle size distribution, SOC, EC, CEC, TN, pH, N, P, K, Ca, S, Mg, Mn and Zn across the landscape zones. It was observed that soil parameters such as pH (6.62 – 7.44), CEC (27.59 – 32.82 meq/100 g), and EC (90.12 - 121.93 µS/cm) were in the adequate and acceptable range while SOC (0.89 – 1.89 %) was observed to be in low amount. Other nutrients such as N (0.09 – 0.14 %), P (9.46 – 14.87 mg/kg), and K (175.91 - 293.5 mg/kg) were in inadequate amounts except for the S (12.9 – 15.43 mg/kg) which was in optimum, Ca (3117.5 - 4155.31 mg/kg) ranged between low to optimum, and Mg (556.95 - 603.26 mg/kg) was in excessive amounts. However, Mn (114.13 mg/kg – 128.95 mg/kg) was in excess. This study found that, there is a significance difference on soil fertility status across the landscape. Major soil nutrient fertility constraints found were N, P, Ca, and K for some soils. The study recommends that interventions to address the issue of soil fertility in the northeast Maasai landscape should consider the altitude issue due to variations in soil health and nutrient content.