Studies On The Effect Of Fertilizer Application On Nutrient Metabolism And Characteristics Of Photosynthesis In Summer Maize

The effect of fertilizer application on the growth and development of summer maize and the absorption, distribution and remobilization of Nitrogen, Phosphorus, and Potassium were investigated in field-grown conditions from 1997 to 1998, as well as the response of photosynthesis to eco-physiological factors in the corn canopy caused by different fertilizer amounts were explored. The main results were as follows:1. The application of N accompanied with K could improve the absorption of N and K, and increase the amount of the dry matter transferred into kernel at the late stage. While the application of N accompanied with P could improve the uptake of P, making the absorption of K declined. The result indicated that N, K applied mixedly was better that N, P applied together under this experimental condition. The fertilizer containing N, P, and K, however, could increase the absorption amounts of N, P, and K at the same time. When the ratio of N to P to K is 2:1:1, both the nutrients taken up by corn plant and the dry matter weight per plant were the largest in all the treatments, especially at the post growth stage, and leaf growing in the treatment of the ratio of N to P to K 2:1:1 containing higher N and K contents at the late stage were helpful to keep the photosynthetic rate higher, thus made higher yield possible.2. The economic yield increased with the increase of fertilizer rates when the ratio of N to P to K was 2:1:1. Under this proportion, the uptake amounts of N, P, and K in the plant showed that the higher fertilizer were applied, the more nutrients were absorbed, and especially at the late stage. Fertilization played a most important role in adding K content, and the least important in P. The content of K in the topsoil layerwould increase whatever the fertilizer amount was, while the contents of N and P increased only in the higher fertilizer treatment.3. The content of available P in the topsoil layer increased obviously in the higher treatment added organic fertilizer. Both nutrients and the dry matter accumulated after silking in the higher fertilizer treatment containing organic fertilizer were higher when compared with corresponding treatment.4. The fertilizer application amounts played an important part in increasing both the total amounts of dry matter and nutrients, although the effect of fertilizer application on the pattern of growth and development and the nutrient uptake were slim. Both optimum ratio of N to P to K and suitable application rates of fertilizer contribute to continue to increase the amounts of dry matter and nutrients, and to remobilize reasonably them to the kernel at the late stage.5. Nitrogen, phosphorus, potassium applied together could prolong the functional day of leaves, increase leaf area index. The leaf would, however, senescence earlier if the nitrogen rates were excessively higher or lower. The fertilizer had a greater effect on prolonging the functional day in the late stage than increasing the leaf area index in the early stage.6. Fertilizer Application improved the photosynthetic ability of summer maize mesophyll cell, which made the limiting factor of photosynthetic rate from nonstomatal limitation to stomatal limitation gradually, enhanced photosynthetic rate at the post-stage, prolonged the high photosynthesis period, and raised photosynthetic ability in the afternoon. In the field-grown condition, the main eco-physiological factors affecting photosynthetic rate (Pn) were photosynthetic activity radiation (PAR) and stomatal conductance (Sc), which had positively direct effects on photosynthesis. PAR and transpiration rate (Tr) were eco-physiological factors significantly correlated with Pn.