Browsing by Author "Dias Paiao, Gabriel"

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    Can Active Canopy Sensing Technologies and Soil Nitrogen Content Help Us Improve Corn-Nitrogen Management in Minnesota?
    (2017-01) Dias Paiao, Gabriel
    We evaluated the utility of different canopy sensing tools alone or adjusted with soil nitrogen (N) content to estimate corn grain yield and N requirements at various corn development stages. Canopy sensing measurements with SPAD, GreenSeeker NDVI (GS-NDVI), RapidSCAN NDVI and NDRE (RS-NDVI and RS-NDRE) were obtained at V4, V8, V12 and R1 development stages, and soil NO3--N concentration was measured at V4 stage. RS-NDRE had the best predictive power of grain yield and N requirements. Canopy sensing at V4 growth stage had the lowest utility to help improve corn N management. At later development stages, sensor’s performance was superior, but there is less flexibility to apply N. Applying N from V4 to V8 provided the best potential for sidedress application timings. Soil NO3--N measured at V4 stage from 0-30 cm depth showed potential by itself or in combination with early-season sensor measurements to improve corn fertilizer N.
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    Soil Drainage and Tillage Practices: Implications for Nitrogen Management in Upper Midwest Corn and Soybean Production
    (2021-12) Dias Paiao, Gabriel
    In addition to affecting corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) productivity, soil drainage and tillage practices may also influence the soil nitrogen (N) cycle and the need for N fertilizer application. This seven-year study conducted near Wells, MN investigated the influence of drainage condition (drained and undrained), tillage practice (conventional tillage [CT], strip-tillage [ST], and no-tillage [NT]), and N management (varying N rates and application timings) on corn and soybean grain yield, corn optimal N fertilizer rates (ONR), and residual soil N content. Additionally, this study investigated the utility of in-season soil N content and canopy sensing to guide N fertilizer application for corn production. Overall, grain yield in drained compared with undrained soils was 7.6% greater for corn (12.8 vs. 11.9 Mg ha-1) and 2.2% greater for soybean (4.7 vs. 4.6 Mg grain ha-1). For corn, CT and ST in drained soils consistently produced the greatest grain yield, while NT in undrained soils produced the lowest (1.7 Mg grain ha-1 difference). A similar trend was observed for soybean, but the differences were smaller and less frequent (0.3 Mg grain ha-1 difference). These results highlight that drainage and tillage have a larger influence on corn grain yield than on soybean and emphasize that ST is a possible conservation tillage practice option to NT for both corn and soybean. Drainage condition influenced the ONR more than tillage practice. Overall, relative to undrained, drained soils had 16% lower ONR (160 vs. 193 kg N ha-1) and 3.1% greater grain yield at ONR (13.5 vs. 13.1 Mg ha-1), indicating that a large portion of the grain yield losses observed for corn in undrained soils may be related to N deficiency. Compared to split N applications (pre-plant/V6 stage), a single pre-plant N application lowered the ONR in drained soils (151 vs. 168 kg N ha-1), while the opposite occurred for undrained soils (206 vs. 189 kg N ha-1). There were no differences in residual soil N related to drainage condition or tillage practice. These results indicate a greater N use efficiency in drained soils than in undrained, and that split N applications are a better alternative to a single pre-plant application only for undrained soils. Overall, canopy sensing at the V10 stage underestimated the ONR by 22 kg N ha-1, while the maximum return to N (MRTN) underestimated by 61 kg N ha-1. These results show that there is potential for the implementation of sensor-based N management in the Upper Midwest, especially for undrained soils, where there is more variability in the crop N requirement. There were no differences in in-season soil N content at the V6 stage for the different drainage-tillage combinations, indicating that the differences in grain yield and ONR may be related to differences in root development that affect N uptake, regardless of its availability in the soil. Soybean response to N application was variable and produced inconsistent interactions with drainage condition and tillage practice. Overall, N application increased soybean grain yield by 2.5% (0.12 Mg grain ha-1) and oil content by 1.0% (2 g kg-1), but decreased protein content by 1.8% (7 g kg-1) and profit margin by 2.5% ($44.7 ha-1). Similarly, N application to the previous corn crop had little influence in the soybean grown in rotation. The results from this study substantiate the benefits of artificial drainage for corn and soybean production, the fact that ST is a viable conservation tillage alternative to NT, the need to incorporate drainage condition into corn N management guidelines, and the small utility of N application for soybean production.