A Collection of three Independent Studies: Investigating the Impact of Starter Fertilizer on Maize Growth & Development, Validating an Alternative Root Study Method, and Testing the Efficacy of Biostimulants in Maize Production
Abstract
Starter fertilizer applied with or near the seed at planting often enhances early season maize growth (Zea mays L.) but does not always result in higher grain yield. Other responses to starter fertilizer, such as reduced thermal time to reach silking, which suggests accelerated plant development, have been documented. The objective of this study was to examine the relationship between dry matter production and accelerated plant development with respect to 5x5 cm starter (ST) and in-furrow popup (PU) fertilizer. A field experiment was conducted in 2016 with three atplanting treatments consisting of one single rate and formulation of ST (53 N and 21 P kg ha-1 ) or PU (4 N and 6 P kg ha-1 ), and an untreated control. In 2018, the study included four additional siteyears with treatments consisting of an intermediate (ST) or high (STH) starter fertilizer rate, and an untreated control. For ST treatments, depending on location, nitrogen (N) and phosphorus (P) fertilizer rates ranged between 26-28 and 6-10 kg ha-1 , respectively, and for STH treatments N and P fertilizer rates ranged between 47-56 and 12-20 kg ha-1, respectively. In 2016, as new leaf collars appeared, dry matter increased exponentially, but at an equal number of leaf collars ST and PU had similar dry matter as the control. In 2018, dry matter for ST, STH, and control was also similar when normalized for leaf collar number at each site. Overall, these results suggest that enhanced dry matter at a given point in time from ST, STH, or PU was a function of accelerated leaf development as opposed to physically more robust plants of the same leaf collar number. Grain yield was unaffected by ST, STH, or PU treatments at any site-year. Methods used to study roots in crop fields have included extracting soil cores, excavating entire root systems, using radioactive and non-radioactive chemical tracers, or using minirhizotrons. However, due to the intensive nature, level of difficulty, and cost associated with these methods, their use in crop fields has been minimal. We developed an alternative method to quantify maize rooting density over time. The method involved perforated cylinders installed vertically into the soil at different distances from the row, which made roots growing into the cylinder voids visible from the soil surface and possible to count [root number density (RND)] at different depths using a video recording device (1m-long borescope). The objective of this study was to determine if the cylinder method could quantify rooting density throughout the growing season (V3, ~V7, and R2-R3) similar to the more intensive soil core method, compared in two starter fertilizer trials [continuous maize (M/M) and maize/soybean (M/S) rotation]. Cylinders were constructed with perforated (49% voids) polypropylene resin to an inside diameter of 2.58 cm and a length of 30 cm. Cylinders were painted with red and green alternating markings (5 cm) on the outside and inside walls to visually aid in identifying depth from the soil surface. After plants emerged, cylinders were inserted vertically into the soil after drilling a 3.5 cm diameter borehole.
Degree
Ph.D.
Advisors
Camberato, Purdue University.
Subject Area
Agriculture|Plant sciences
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