Response of Maize Grown Under High Plant Density; Performance, Issues and Management - A Critical Review

Abstract

Modern cropping is based on relatively high plant density. The improved grain yield per unit area of modern maize (Zea mays L.) hybrids is due to the increased optimum plant population rather than the improved grain yield per plant. High plant density has been widely used to enhance grain yield in maize. Subsequently we review the effect of planting density on physiology, phenology, morphology, nitrogen use efficiency, water use efficiency grain yield information in maize crop. At higher plant populations reduced grain yield also results from the increased pollento-silking interval and the following barrenness. However, it may lead to higher risk lodging hence causing significant yield loss of the crop. Future insights are morphological and physiological basis controlling barren and stalk lodging resistance. How root traits, and anatomy of sheath and stem of maize plants correspond to high plant population and a further study on the physiological and biological basis of organ development that may govern the mechanisms of high plant density would be essential for future research.

Non-Structural Carbohydrate Metabolism, Growth, and Productivity of Maize by Increasing Plant Density

“…This difference would justify why maize productivity usually is enhanced by increasing plant density (Figure 5a) even though individual plant growth (Figure 2a) and kernel production per plant is decreased by interplant competition (Figure 5c,d). This statement is supported by other studies suggesting that an increase in maize kernel productivity should be related to the increase in LAI values [8,9,13,14,16,34].…”

“…The dry weight of stalk was more sensitive to the effect of increases in plant density than that of leaves and kernels (Figure 2a), with respectively 40%, 27%, and 21% reductions. This increased sensitivity of stalk dry weight compared to the dry weight of other plant parts as a function of plant density was not found in previous critical reviews on this subject [6,16]. This sequence of decreasing effects suggest that plants in the stage of grain filling, and under increasing competition due to the increase of density, directs photoassimilates mainly to the kernels (sink), with the leaves (source) being the second priority and the stalk being the lowest priority, in order to maintain the production of photoassimilates demanded by kernels.…”

“…This sequence of decreasing effects suggest that plants in the stage of grain filling, and under increasing competition due to the increase of density, directs photoassimilates mainly to the kernels (sink), with the leaves (source) being the second priority and the stalk being the lowest priority, in order to maintain the production of photoassimilates demanded by kernels. Naturally, this fact can lead to the well-known problem of stem weakening and the loss of productivity by plants lodging under high plant densities [6,16]. Other authors verified that the increase in plant density reduces the duration of stalk internode thickening and dry matter accumulation [13], which helps to explain the results observed for stalk tissue (Figure 2a).…”

“…Also, increasing plant density leads to an increase in plant competition for nutrient, water, light, and causes morphological alterations in corn plants [8,13,14,34]. So, it could be supposed that variables such as non-structural carbohydrates concentration and accumulation, as well as the activity of enzymes involved in carbon metabolism in leaves, stalk, and kernels, would also greatly change to sustain the increases in productivity, reported up to relatively high plant densities [6,16]. In this research, we submitted maize plants to different crop densities, from 30,000 to 90,000 plants ha −1 , aiming to study the expected changes in those variables.…”

“…However, the understanding of how plant physiology works to perform those small increases is very important to drive new technologies for productivity enhancement. As a result, this issue has recently attracted the attention of many researchers in this area [11][12][13][14][15][16][17]. There are suggestions that even though carbohydrate reserves do not directly increase yield potential in maize plants under normal conditions for growth, they contribute to yield stability when plants are challenged by environmental or biotic stresses [2,6].…”