An experiment was conducted to evaluate the residual effect of inorganic fertilizer and bioslurry application on biological yield and nutrient content of Swiss chard. The study was conducted at Döhne Agricultural Development Institute (DADI) (32°31’ 34.077” S; 27°27’ 37.473” E) in Stutterheim, Eastern Cape, South Africa. Following planting and harvesting of two Swiss chard cultivars (Fordhook giant and Star 1801) in soil incorporated with 10 L Bioslurry (50% Bio), 20 L Bioslurry (100% Bio) and 40 L Bioslurry (200% Bio), NPK 2:3:4 (30) and 0 application (control), Swiss chard was planted in the same plots without any fertilizer applications. One seedling was planted per hill and the intra and inter row spacing was 0.25 and 0.5 m, respectively. The postharvest soil analysis showed that plots that were previously treated with 40 L (200%) Bioslurry had relatively higher soil nutrient elements compared to other treatments. The interactive effect of residual fertilizer and cultivar showed that the plots previously treated with NPK 2:3:2 (30) resulted into significantly higher dry leaf mass in Star 1801 but this effect did not differ significantly with 20 L (100%) and 40 L (200%) Bioslurry in Fordhook giant. The effect on soil pH revealed that the application of fertilizers resulted in reduced pH levels in summer compared to winter irrespective of the treatment. The plant mineral analysis showed that the fertilizer residues did not significantly influence plant mineral uptake and no clear trends were observed for the tested elements.
Key words: Residual effect, bioslurry, biological yield, Fordhook giant, Star 1801.
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