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Scientific publications

A series of scientific papers and conference proceedings have been published by the FIGARO partners:

Here below the scientific papers from FIGARO partners submitted and under approval by publishers:

  • Yield, irrigation and N use efficiency of table potato affected by different split-N fertigation regimes in sandy soil, Zhenjiang, Z., Plauborg, F., Andersen, M.N., submitted to Field Crops Research.

Abstract: To explore the response of yield, crop growth as well as water and N use efficiency to different 27 fertigation regimes, three years field experiment were carried out. The factors in the experiment 28 comprised five N levels providing 0, 60, 100, 140 and 180 kg N ha-1, and one real time model-based 29 N fertilization method, as well as three irrigation levels. Results showed that prolonged N 30 fertigation increased yield consistently but N fertigation should be carried out early so that shoot 31 growth is optimized and prolonged N have sufficient time to take effect on tuber yield accumulation. 32 In all three years, the highest fresh yield and marketable yield was obtained when 180 kg N ha-1 was 33 applied. Compared to the 180 kg N ha-1 treatment, real-time model-based N fertilization resulted in 34 similar yield in all seasons. The model-based regime saved 60-88 kg N ha-1 and resulted in 35 significantly higher physiological N use efficiency in 2013 and agronomic N use efficiency in 2014, 36

highlighting the feasibility of using Daisy model for guiding in-season N fertigation. In case of non-37 availability of soil and weather parameters to simulate N dynamics by Daisy, a total amount of 100 38 kg N ha-1 is recommended for N fertigation, since significant difference of yield was not found 39 among N range of 100-180 kg N ha-1. Deficit irrigation did not cause reduced soil water content, 40 ratio vegetation index (RVI) and yield, but irrigation efficiency was increased significantly in 2013.

  • Using ground-based remote sensors to estimate N status of potato under different fertigation regimes, Zhenjiang, Z., Andersen, M.N., Plauborg, F., submitted to Remote Sensing of Environment.

Abstract: Two years experiments were set up to evaluate the performance of different vegetation 7 indices (VI) to estimate shoot N concentration (Nc) and shoot dry matter (DM) for a potato 8 crop grown under different nitrogen (N) treatments. Possibilities to improve the performance 9 of VI using normalization by leaf area index (LAI) or ground cover fraction (GC) were also 10 investigated. Results indicated that Nc was significantly correlated to RRE (Near-infrared 11 divided by red edge reflectance) and RRE/GC with a coefficient of determination (R2) of 0.62 12 and 0.78, respectively, indicating that inclusion of auxiliary parameter GC together with RRE 13 substantially improved the correlation as compared to using only RRE. However, no 14 significant correlation between Nc and RVI (Ratio Vegetation Index, near-infrared divided by 15 red reflectance) or NDVI (Normalized Difference Vegetation Index) was found. Besides, DM 16 was highly correlated to RVI and NDVI. Moreover, GC showed significant relationship 17 (R2=0.86) with DM, highlighting its versatile usefulness in estimating agronomic variables 18 DM and Nc, which are the core variables to assess N status of crops for a better N application.

  • A RVI/LAI-Baseline to Detect N Stress and Guide N fertigation Using Combined Information from Spectral Reflectance and Leaf Area Measurements in Potato, Zhenjiang, Z., Andersen, M.N., Thomsen, A.G., Plauborg, F., submitted to Precision Agriculture.

Abstract: More user-friendly methods are needed to detect crop N status/stress and guide the timing of in-season N application. In the 7 current study, a reference line method of detecting N stress was proposed to remedy practical problems of methods that require 8 leaf sampling or maintaining a N sufficient strip in the field. The reference line method was derived from the integrated 9 information of ratio vegetation index (RVI) and leaf area index (LAI), which were obtained from field experimental potato crops. 10 Different N treatments received 42 kg N/ha at planting and, subsequently, the rest of N was applied during the season. The total 11 N ranged from 0 to180 kg N/ha. RVI and LAI from the economically optimum 180 kg N/ha treatments was used to derive the 12 reference line. RVI and LAI from 180 kg N/ha treatment had a high (R2=0.97) correlation and were best fitted with a 2nd order 13 polynomial function, which was independent of season. The treatments where N fertigation was stopped before reaching 180 kg 14 N/ha started to deviate from the 95% confidence interval of the reference line about 10 days after N-fertigation was stopped. This 15 corresponded to 10-20 kg/ha difference in total plant N uptake between reference and the N deprived treatments, implying that a 16 deviation from the reference line occurred for small N deficits. Besides, running crop simulation model to alert for impendent N stress closely corresponded to the reference line and was recommended as a second management tool. Therefore two tools are 18 hereby made available to guide supplementary N-fertilization. These will be helpful in regional potato production for diagnosis 19 of N status, and allow discrimination between situations of sub-optimal and optimal N supply.