Optical crop sensor for variable-rate nitrogen fertilization in corn: i - plant nutrition and dry matter production

Abstract

SUMMARYVariable-rate nitrogen fertilization (VRF) based on optical spectrometry sensors of crops is a technological innovation capable of improving the nutrient use efficiency (NUE) and mitigate environmental impacts. However, studies addressing fertilization based on crop sensors are still scarce in Brazilian agriculture. This study aims to evaluate the efficiency of an optical crop sensor to assess the nutritional status of corn and compare VRF with the standard strategy of traditional single-rate N fertilization (TSF) used by farmers. With this purpose, three experiments were conducted at different locations in Southern Brazil, in the growing seasons 2008/09 and 2010/11. The following crop properties were evaluated: above-ground dry matter production, nitrogen (N) content, N uptake, relative chlorophyll content (SPAD) reading, and a vegetation index measured by the optical sensor N-Sensor ® ALS. The plants were evaluated in the stages V4, V6, V8, V10, V12 and at corn flowering. The experiments had a completely randomized design at three different sites that were analyzed separately. The vegetation index was directly related to above-ground dry matter production (R 2 = 0.91; p<0.0001), total N uptake (R 2 = 0.87; p<0.0001) and SPAD reading (R 2 = 0.63; p<0.0001) and inversely related to plant N content (R 2 = 0.53; p<0.0001). The efficiency of VRF for plant nutrition was influenced by the specific climatic conditions of each site. Therefore, the efficiency of the VRF strategy was similar to that of the standard farmer fertilizer strategy at sites 1 and 2. However, at site 3 where the climatic conditions

Optical crop sensor for variable-rate nitrogen fertilization in corn: II - indices of fertilizer efficiency and corn yield

“…The treatments, experimental design, site locations, soil, and climate characteristics were previously reported in Bragagnolo et al (2013).…”

“…Corn grain yield was assessed on the basis of corn cobs collected from 2 m in two rows of corn close to the georeferenced sampling points, where the plant vegetative properties were evaluated (Bragagnolo et al, 2013). Grain yield samples were collected at nine georeferenced points per treatment (distance of 40 m between each plot) at site 1, while at site 2 samples were collected at 12 georeferenced points per treatment (distance of 20 m between each plot), and at site three samples were collected at seven georeferenced points per plot (distance of 40 m between plots).…”

“…However, climatic conditions can affect soil N availability (Bragagnolo et al, 2013), crop residue input (Amado et al, 2002), and corn N use efficiency (NUE) (Melchiori et al, 2005), resulting in temporal variability of the crop N requirements. Consequently, the crops will require adjustments of the N fertilization strategy during the season (Melchiori et al, 2005;Singh et al, 2006).…”

“…Among the optical sensors commercially available, the Yara N-Sensor ® ALS (Yara International ASA) has been used successfully in different crops (Jasper et al, 2009;Portz et al, 2012;Bragagnolo et al, 2013).…”

An Empirical Exponential Model based on Reflectivity Measurements for Soil Nitrogen Detection

“…The efficiency of VRF was influenced by climatic factors. Also, a comparison was made between the conventional single rate nitrogen fertilization [12].Several studies are being made for specific crops like tea regarding their soil nutrient needs on a larger scale. The data so available can be used to build up sensor systems which can directly influence precision farming in a big way.…”