Abstract
ABSTRACT The objective of this study was to evaluate the effect of growth reducer and nitrogen fertilization on morphological variables, SPAD index, radiation interception, and grain yield of three cultivars of wheat. The experimental design was a randomized block in factorial scheme 3x5x2, with three cultivars (Mestre, Iguaçú and Itaipú), five nitrogen doses (0, 40, 80, 120, 160 Kg ha-1), and application or no application of a growth reducer, with three replications. The following characteristics were evaluated: plant height, SPAD index, leaf area index (LAI), Global Radiation Interception (GRI) and grain yield. The Tukey test (p < 0.05) was used for the comparison between the means of cultivar and growth reducer factors, and for a regression analysis to evaluate N levels. Increasing the dose of nitrogen promotes an increase in LAI of plants of wheat crops differently among cultivars, which leads to a greater degree of global radiation interception. At doses higher or equal to 120 Kg ha-1 of nitrogen, there are significant differences in grain yield between treatments with and without the application of the growth reducer. The significant interaction between growth reducer and nitrogen dose, showed that applications of growth reducer increase the GRI at doses above and below 80 Kg ha-1 of nitrogen. Nitrogen rates of 138 and 109 Kg ha-1 are responsible for maximum grain yields of wheat, which is 4235 and 3787 Kg ha-1 with and without the use of growth reducer, respectively.
Highlights
The response of wheat (Triticum aestivum L.) to nitrogen fertilization in grain productivity depends on the amount of nitrogen (N) applied, since the use of high amounts of N can lead to increased vegetative growth, which causes lodging of the plants and affects yield and grain quality (Buzetti et al, 2006).Among the strategies for use of high doses of nitrogen in wheat, there is the application of growth reducers
There was an effect of the interaction cultivar x dose on the SPAD index, leaf area index (LAI) and the global radiation interception (GRI), of cultivar x reducer on the height and of dose x reducer on the LAI, GRI and productivity
Regarding the Tukey test (Table 1), it can be seen that the cultivars showed difference in the SPAD and the LAI from the doses of 40 and 80 kg ha-1, respectively, and the cultivar Mestre showed higher values of SPAD index in most doses compared with Itaipú and Iguaçú
Summary
The response of wheat (Triticum aestivum L.) to nitrogen fertilization in grain productivity depends on the amount of nitrogen (N) applied, since the use of high amounts of N can lead to increased vegetative growth, which causes lodging of the plants and affects yield and grain quality (Buzetti et al, 2006).Among the strategies for use of high doses of nitrogen in wheat, there is the application of growth reducers. From the assumption, observed by Lozano & Leaden (2002), that trinexapacethyl, besides reducing plant growth, is able to modify the leaf architecture, mainly of wheat flag leaf, we emphasize the importance of verifying if it influences the overall amount of global radiation intercepted by the plant and, the photosynthetic rate and productivity of wheat grain. Knowledge of the influence of these factors (nitrogen doses and growth reducer) on the global radiation interception (GRI), as well as on other variables that modify the amount of radiation intercepted by the crop, such as leaf area index (LAI), SPAD index and plant height, can bring relevant information to increase productivity of wheat, by reason of greater use of global incident radiation on the plant canopy. The aim was to evaluate the effect of growth reducer and nitrogen fertilization on morphological variables, SPAD index, global radiation interception and productivity of three wheat cultivars
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