Organic substrates and slow-realease fertilizing on nutrient accumulation and absorption efficiency of custard apple seedlings

There is a lack of agronomic research on the production of custard apple seedlings, especially regarding the ideal substrate and nutritional requirement of the plants. In order to evaluate the accumulation of nutrients in shoots and roots, leaf chlorophyll index and absorption efficiency index (AEI) in custard apple seedlings grown in different substrates and under doses of slow-release fertilizer, an experiment was set in randomized blocks in split-plot scheme with four replicates and eleven plants per plot. The custard apple seedling production method was by sowing. Plots were represented by substrates (fresh sugarcane bagasse; enriched sugarcane bagasse; coconut powder, and commercial organic substrate), whereas subplots were represented by Osmocote Plus® fertilizer doses (0; 3; 6; 9; 12 and 15 kg m-3). The final evaluation was performed at 105 days after sowing. The effect of the slow-release fertilizer on the formation of custard apple seedlings was influenced by the substrate. There was greater accumulation of nutrients as the availability of nutrients increases, as well as increase in nutrient AEI. Custard apple seedlings were found to be more efficient to absorb N > Mg > K > Ca > P > Fe > Mn > Zn. As substrate, coconut powder associated with the 9 kg m-3 slow-release fertilizer dose is recommended to produce custard apple seedlings.