G x E x M
The favorite set of letters for every agronomist you'll ever talk to.
Genetics, Environment, & Management - these categories effectively encompass what causes a plant to respond the way it does. Genetics describe the core makeup of a plant (the species, hybrid, cultivar, etc. - its identity). Environment describes what that unique plant is exposed to (water, soil type, temperature, etc. - its surroundings). Management describes the human intervention in the plant's life (tillage, introduced fertilizer, plant population, etc. - its treatment).
Plant responses can be described by these terms, and tillering is no different!
As shown in the picture below, there are five main factors that affect the development of tillers (initial appearance, seasonal growth, and final productivity), each of which fall into the categories mentioned above!
Light. The amount of sunlight that is able to reach the crown at the base of the plant is crucial to the development of tillers. Read So what's a tiller anyway? for more information on crowns! Low light (shading) signals to a plant that competition is present (i.e. "Hey, there are leaves above you!"), and tillers may not develop. An important application of this concept is found in management strategies involving low plant densities. By spacing plants further apart, more light is able to reach ground level, and this practice ultimately encourages tiller development.
Genetics. As discussed in my The corn conundrum and So what's a tiller anyway? posts, different species tiller differently. Alfalfa and sorghum are very different from each other although both have crowns and produce tillers, for example. This also goes deeper than the species level, as different hybrids within a species can have different tillering tendencies!
Water. Moisture is usually a key limiting factor in cropping scenarios. Plants are "smart" with their resources, and will react accordingly to conserve them if necessary. If a plant does not have ample moisture, tillers may not develop. Similarly, if a plant becomes stressed due to a lack of water, unnecessary tillers will likely be the first "drain" to go. That is, the plant may abort them. This is a key item to consider in situations where water is a concern, such as for this project!
Temperature. Temperature has been shown to have an effect on the appearance of tillers and how growing tillers develop. Cooler temperatures generally favor tiller development.
Fertility. As mentioned in the Water section, plants react appropriately to the resources they have available to them. A stressed plant will not put additional energy into producing tillers if it already cannot sustain itself. Ample nutrients in the soil, nitrogen for example, will encourage tiller development.
It is important to note that just because all of the ingredients are right, tillers will not always develop. In corn specifically, we still have a lot to understand about how all of these pieces fit together!