Heavy metals in water sources can threaten human life and the environment. The analysis time, need for chemical reagents, and sample amount per analysis assist in monitoring contaminants. Application of the Fourier Transform Infrared (FT-IR) Spectroscopy for the investigation of heavy metal elements has significantly developed due to its cost effectiveness and accuracy. Use of chemometric models such as Partial Least Square (PLS) and Principle Component Regression Analysis (PCA) relate the multiple spectral intensities from numerous calibration samples to the recognized analytes. This study focused on the FT-IR calibration and quantification of heavy metals (Ag, Cd, Cu, Pb and Zn) in surveyed water sources. FT-IR measurements were compared with the atomic absorption spectrometer (AAS) measurements. Quantitative analysis methods, PCA and PLS, were used in the FT-IR calibration. The spectral analyses were done using the Attenuated Total Reflectance (ATR-FTIR) technique on three river and four borehole water sources sampled within two seasons in QwaQwa, South Africa (SA). The PLS models had good R² values ranging from 0.95 to 1 and the PCA models ranged from 0.98 to 0.99. Significant differences were seen at 0.001 and 0.05 levels between the PLS and PCA models for detecting Cd and Pb in the water samples. The PCA models detected Ag concentrations more (˂0 mg L⁻¹ on selected sites). Both the PLS and PCA models had lower detection only for Zn ions mostly above 45 mg L⁻¹ deviating from the AAS measurements (<0.020 mg L⁻¹). The FT-IR spectroscopy demonstrated good potential for heavy metal determination purposes.

Sub-Saharan Africa (SSA) agriculture is characterized by dependence on erratic rainfall, inadequate conservation practices, and a decline in soil fertility resulting in low crop productivity. Therefore, conservation agriculture (CA) has been proposed as an alternative to improve soil fertility and productivity. Hence the aim was to investigate the effects of tillage systems, fertilization, and cropping patterns on selected soil chemical properties (pH, organic carbon, total nitrogen, extractable phosphorus, exchangeable cations, and cation exchange capacity) and identify which cropping pattern maximizes stover and grain maize–legume productivity and land use. A two-year (2016/17–2017/18) field experiment in a loamy sand soil was conducted at Nhacoongo Research Station, southern Mozambique. Two tillage systems (conservation (CA) and conventional tillage (CT)), two fertilization treatments (fertilized and unfertilized), and seven cropping patterns (four sole crops and three maize–legume intercrops) were evaluated in a randomized complete block design with split–split plot arrangement and replicated four times. CA practices resulted in significantly higher soil chemical properties and increased stover and grain yields as compared to CT practices, but fertilization demonstrated insignificant effects on soil chemical properties and significant influences on stover and grain yield of maize and legumes. Cropping patterns induced no significant effect on soil chemical properties and either stover or grain yield. Estimated indices like land equivalent ratio (1.18–2.67) and competitive ratio index (0.01–1.72) confirmed the advantage of intercropping against sole cropping. This is largely supported by the estimated values of aggressivity and relative crowding coefficient. Smallholder farmers can therefore benefit by adopting CA.

Farmers continuously remove crop residues for use as building materials, fuel and animal feed or bedding as well as to avoid difficulties during tillage operations. Therefore, demonstrations of the benefits of recycling crop residues are necessary. The aim with this study was to evaluate the influence of different wheat production management practices on acidity and some essential nutrients from a long-term trial on a Plinthosol in semi-arid South Africa. The trial was set up in 1979, and since then two methods of straw management (unburned and burned), three methods of tillage (no-tillage, stubble mulch, and plough), two methods of weed control (chemical and mechanical), and three levels of nitrogen (N) fertiliser (20, 40 and 60 kg ha–1) have been applied. Soil samples were collected in June 2010 at depths of 0–50, 50–100, 100–150, 150–250, 250–350 and 350–450 mm from plots that received 40 kg N ha–1 and were analysed for pH, phosphorus (P), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn). Results obtained showed that straw burning resulted in higher P and Mn but lower Cu than no-burning. No-tillage, and to some extent stubble mulch, suppressed soil acidification and increased P and Zn compared with ploughing, especially in the surface layers where crop residues accumulate. In contrast, mouldboard ploughing and stubble mulch increased Cu more than no-tillage, possibly due to the strong affinity of organic matter for Cu. Tillage effects on Mn were inconsistent and difficult to explain. Chemical weeding also improved P, probably because of the pesticide application, but resulted in lower pH and Cu values compared with mechanical weeding. Treatment combinations also had an influence on P and, to a lesser extent, on soil pH and Cu, which might be due to the higher organic matter present in no-tilled soils. Irrespective of straw management or weed-control methods, no-tillage resulted in higher P than did ploughing and stubble mulch. Nutrient concentrations and pH values were sufficient for wheat growth under all treatments. However, although the nutrients were highest under straw burning, no-tillage and, to some extent, stubble mulch, wheat yield was higher with unburned straw and mouldboard ploughing. Therefore, an integrated approach from various disciplines is recommended to identify and rectify yield-limiting factors under conservation tillage systems.

Changes in soil fertility indicators are mainly the result of management practices and usually influence crop yields over the long term. This study shows the effects of long-term wheat production management practices on exchangeable base cations and cation exchange capacity (CEC). Applied field treatments included two methods of straw management (unburned, burned), three methods of tillage (no tillage, stubble mulch, plowing), and two methods of weeding (chemical, mechanical). Samples were collected at six soil depths and analyzed for potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), and CEC. Burned wheat straw resulted in greater K and lower Ca concentrations compared to unburned wheat straw. No-tillage treatment increased K, Ca, Mg, Na, and CEC compared to both stubble mulch and plowing. Chemical weeding improved Na and CEC compared to mechanical weeding. The treatment combinations had positive influences mainly on CEC. Unburned straw and moldboard plowing with respect to burned straw and no tillage enhanced grain yield with 8%.