Sustainable Use of Spent Mushroom Substrate: Nutrient Contributions across Growth Phases of Cucurbit Crops

This research aims to assess nutrient changes in fresh and mature SMS in pre-harvest, during harvest, and post-harvest cycles of cucurbit crops. To evaluate the nutrient availability, depletion, and nutrient retention during the crop growing period, the crop nutrient requirement, namely Nitrogen (N), Phosphorus (P), and Potassium (K), was analyzed. The results suggest that fresh SMS with an initial high in N carried good N availability for vigorous early growth, but had quicker nutrient depletion, especially K, at the fruiting stage. Aged SMS, in contrast, put out K, calcium, and magnesium at a steadier pace and duration, thus providing an optimal quality of fruits and yields. Comparative assessment of underage and overaged SMS indicated that overaged SMS had a higher nutrient retention capability, hence was much more appropriate as a long-term soil fertility enhancer. The study also discussed different approaches to nutrient recycling, with a stress on the reuse of the substrate and the addition of organic matter for multiple growing cycles. Fresh SMS gave higher initial N content (514 ppm) and K content (468 ppm) to encourage early growth of the plant in pre-harvest stage. In the active growth phase, nutrient deficiency was most pronounced on N and K, the elements that are critical for cucurbit fruits and leaves. Fresh SMS treatments maintained higher N levels (832 ppm in Soil (4): New (2)), but they showed more rapid K loss. In contrast, aged SMS treatments, particularly Soil (4): Old (2), stored more K (692 ppm), which is an essential nutrient for fruit development and better crop quality. Post-harvest analysis showed that fresh SMS left higher residual N levels (862 ppm in Soil (4): New (2)). This shows that not all the N was used by the crops, as the value was only 2 out of 15. The results make it possible to give much attention to proper management of the substrate in achieving better yields of cucurbit crops and the soil.