Maize (Zea mays L.) grain yield levels and the response to fertilizer nitrogen (N) are expected to change from year to year and from location to location. Because yield level and N response have been documented to be independent and are known to infl uence N demand, optimum N rates at the same location vary each year due to unpredictable changes in the environment. Th e objective of this study was to further analyze maize grain yield levels and optimum fertilizer N rates from published data in maize growing regions of the United States. Optimum N rates were determined by calculating the diff erence in N uptake between the highest-yielding plot and the check plot (no N applied [0-N]). Th e diff erence in grain N uptake between the fertilized plot and the 0-N check plot was then divided by 0.33 (the assumed average N use effi ciency) to estimate optimum N rate by site and year. For the 213 site-years of data included in this study, grain yields in both the high N rate and check (0-N) plots were highly variable. Optimum N rates fl uctuated from year to year at all locations. Optimum N rates were not highly correlated with the high-N rate yield (R 2 = 0.20) or 0-N check yield (R 2 = 0.16). Th e wide range in optimum N rates observed in all maize experiments suggests the need to adjust N rates by year and location. A potential solution is to use midseason sensor-based technologies that can accurately predict yield potential and simultaneously encumber N responsiveness known to be independent of yield.Plant and Soil Sciences Dep., 044 N Ag Hall,
Maize planting is normally accomplished by hand in the developing world where two or more seeds are placed per hill with a heterogeneous plant spacing and density. To understand the interaction between seed distribution and distance between hills, experiments were established in 2012 and 2013 at Lake Carl Blackwell (LCB) and Efaw Agronomy Research Stations, near Stillwater, OK. A randomized complete block design was used with three replications and 9 treatments and a factorial treatment structure of 1, 2, and 3 seeds per hill using interrow spacing of 0.16, 0.32, and 0.48 m. Data for normalized difference vegetation index (NDVI), intercepted photosynthetically active radiation (IPAR), grain yield, and grain N uptake were collected. Results showed that, on average, NDVI and IPAR increased with number of seeds per hill and decreased with increasing plant spacing. In three of four site-years, planting 1 or 2 seeds per hill, 0.16 m apart, increased grain yield and N uptake. Over sites, planting 1 seed, every 0.16 m, increased yields by an average of 1.15 Mg ha−1(range: 0.33 to 2.46 Mg ha−1) when compared to the farmer practice of placing 2 to 3 seeds per hill, every 0.48 m.
Decreased atmospheric S deposition in the past 20 yr has led to increased S fertilizer consumption in winter wheat (Triticum aestivum L.). Producers often apply S without any soil test information. Experiments were conducted at Lahoma, Lake Carl Blackwell, and Perkins, OK (2011OK ( -2013 to assess the effect of N and S applied preplant and foliar on grain yield and grain N for winter wheat. In 2011-2012, urea ammonium nitrate (UAN) was applied preplant at rates of 40 and 80 kg N ha -1 additionally; UAN and urea-triazone (NSURE) were foliar-applied at rates of 10 and 20 kg N ha -1 . Sulfur was foliar-applied as gypsum (CaSO 4 ×2H 2 O) at 6 kg S ha -1 . In 2013, trials were altered to apply 40 kg N ha -1 as UAN preplant, and 20 kg N ha -1 foliar-applied. Gypsum rates were adjusted at 0, 3, and 6 kg S ha -1 preplant, and S (MAX-IN-S) at 3 and 6 kg S ha -1 was foliar-applied. Sulfur did not increase grain yield or grain N concentration at any site. The interaction between foliar S and N and preplant S and N was not significant. Sulfur fertilizer application is less likely to benefit this region unless low levels of soil test S are identified before planting. Use of recommended soiltesting guides are encouraged. Although S applications are encouraged commercially, no response was observed in these trials, and all were on sites where soil organic carbon was low (<8.5 g kg -1 ), where the possibility of seeing S deficiency was greater.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.