Residual Effects of Leaf Mulch on Sweet Corn and Rye

When municipal shade tree leaves (MCST-leaf) are used as mulch the residues impact soil fertility for crops in the rotation. Pumpkin (Cucurbita pepo L.), grown near Pittstown, New Jersey, using leaf mulch, was followed in the next year by sweet corn (Zea mays L.) and by a fall-seeded rye (Secale cereale L.) cover crop. A 15 cm layer of MCST-leaf mulch adds an estimated 448 kg ha−1 of N organically bound within 45 Mg ha−1 of leaf dry matter. Because of the high C/N ratio, little of this N becomes available in the first growing season as was apparent from the N immobilization and N deficiency temporarily observed when the land was initially cropped to pumpkin. Sweet corn ear size was increased on amended soil compared to unamended soil. Crop responses with both sweet corn and rye indicated that significant amounts of nitrogen became plant available from leaf mulch decomposition. Leaf mulch improves soil fertility for several years after incorporation but in ways not apparent through soil nitrate testing. Besides enhanced N nutrition, sweet corn ear size on MCST-leaf amended soil may be related to other improvements in soil quality such as increased water holding capacity.