Effect of defoliation and ear removal on dry matter production and inorganic element absorption in sweet corn

Abstract

Sweet corn (Zea mays L. cv. Laramie 83) was grown under field conditions in the experimental field of Hiroshima University to examine the effects of defoliation and ear removal on dry matter and grain production, inorganic element absorption and the nutrient composition of husk leaf and ear leaf. Total dry matter production after silking decreased by the removal of either all the ears or all the leaves on the main culm. Net assimilation rate (NAR) decreased by ear removal but it increased by partial defoliation. These results suggest that photosynthetic ability and grain production during the grain filling period are controlled by the sink capacity.

While husk leaf removal did not affect grain production, husk leaf alone produced about 45 to 80% of grain yield compared to the control plant. The leaf area of the husk leaf accounted for 15-20% of the leaf area of the whole plant and showed a higher NAR than the leaves on the main culm when it remained alone. These results indicate that the potential productivity of husk leaf is higher than that of leaves on the main culm.

With complete defoliation, a slight accumulation of N, P, and Mg was observed, although there was some accumulation of K. The effect of the removal of all the ears however, on inorganic element absorption was less pronounced except for a marked reduction in N increment. These results indicate that the control of the absorption of inorganic elements is affected more strongly by the leaves on the main culm than by the ears. When only the husk leaf remained, a considerable reduction of Ca and N absorption was recorded while K absorption was not affected. Husk leaf is characterized by higher contents of Nand P, and lower contents of K, Ca, and Mg than the ear leaf.

These results suggest that the husk leaf shows a higher potential capacity to produce grains than the leaves on the main culm, whereas, a lower capacity to accumulate inorganic elements except for K.

Key Words:

• defoliation
• grain production
• husk leaf
• inorganic element absorption
• sweet corn