Are neem cake and castor cake useful against soil pests and nematodes?

Neem cake is the residue left after neem oil is pressed from the seed, and it does double duty in the soil, it is a slow release organic manure rich in nitrogen and it has some effect against nematodes, white grubs and other soil pests because of its remaining neem compounds. It also slows down the loss of urea nitrogen when mixed with fertiliser. Apply it at sowing or planting mixed into the soil, commonly a few hundred kg per acre depending on the crop, and keep the soil moist. Castor cake works mainly as a rich organic manure and also has some pest suppressing effect in soil. Be realistic, these cakes reduce soil pest and nematode pressure gradually and improve soil health and microbial life, they are not a quick nematicide for a heavy nematode problem. They work best applied every season as part of building up organic matter, alongside crop rotation and bio control agents like Trichoderma. Make sure the cake is well decomposed or mixed early so it does not harm tender roots, and confirm the per acre rate for your crop with your KVK.