Precision nitrogen management of wheat. A review

Abstract

Conventional farming has led to extensive use of chemicals and, in turn, to negative environmental impacts such as soil erosion, groundwater pollution and atmosphere contamination. Farming systems should be more sustainable to reach economical and social profitability as well as environmental preservation. A possible solution is to adopt precision agriculture, a win-win option for sustaining food production without degrading the environment. Precision technologies are used for gathering information about spatial and temporal differences within the field in order to match inputs to site-specific field conditions. Here we review reports on the precision N management of wheat crop. The aims are to perform an investigation both on approaches and results of site-specific N management of wheat and to analyse performance and sustainability of this agricultural practice. In this context, we analysed literature of the last 10-15 years. The major conclusions are: (a) before making N management decisions, both the measurement and understanding of soil spatial variability and the wheat N status are needed. Complementary use of different sensors has improved soil properties assessment at relatively low cost; (b) results show the usefulness of airborne images, remote and proximal sensing for predicting crop N status by responsive in-season management approaches; (c) red edge and near-infrared bands can penetrate into higher vegetation fraction of the canopy. These narrowbands better estimated grain yield, crop N and water status, with R 2 higher than 0.70. In addition, different hyperspectral vegetation indices accounted for a high variability of 40-75 % of wheat N status; (d) various diagnostic tools and procedures have been developed in order to help wheat farmers for planning variable N rates. In-season adjustments in N fertilizer management can account for the specific climatic conditions and yield potential since less than 30 % of spatial variance could show temporal stability; (e) field studies in which sensor-based N management systems were compared with common farmer practices showed high increases in the N use efficiency of up to 368 %. These systems saved N fertilizers, from 10 % to about 80 % less N, and reduced residual N in the soil by 30-50 %, without either reducing yields or influencing grain quality; (f) precision N management based on real-time sensing and fertilization had the highest profitability of about $5-60 ha −1 compared to undifferentiated applications.

Assessing wheat spatial variation based on proximal and remote spectral vegetation indices and soil properties

“…However, the soil parameters used in this study (Table 2) are rather consistent in time, whereas spectral vegetation indices are intrinsically variable between years, depending on growth conditions affecting canopy reflectance properties (Diacono et al, 2013). Thus, soil analysis supplies data that can be used for more years, whereas spectral vegetation indices need to be assessed each year.…”

“…Proximal indices were assessed in a 36-cell grid (36×36 m; cell size 1152 m²), using two hand held devices: i) the chlorophyll meter N-Tester (NT) (Yara International ASA, Oslo, Norway), which measures leaf transmittance in the red (650 nm) and infrared (940 nm) wavelengths, indicating a numeric value that is proportional to leaf chlorophyll content (Diacono et al, 2013); ii) the active radiometer GreenSeeker (GS) (NTech Industries, Inc., Ukiah, CA, USA), which measures canopy reflectance in the red (RRED) (650±10 nm) and NIR (RNIR) (770 ±15 nm) band, and calcu- lates NDVI as index of general crop status (Raun et al, 2001) according to the formula: NDVI = (RNIR-RRED)/(RNIR+RRED).…”

“…The sustainable improvement of wheat production is strongly associated with the supply of crop inputs in a frame of precision agriculture (PA) practices (Diacono et al, 2013;Yousefi and Razdari, 2015). This means supplementing the wheat crop with the amount of each input that maximises yield in light of spatially-and temporally-variable growth conditions.…”

Effect of Agricultural Land Use on the Water Quality of Polish Lakes: a Regional Approach

“…The new policy of water quality protection and improvement should be based on proper management of the catchment area, and above all on the introduction of appropriate rules for agricultural production aimed at supporting precision farming. Precision agriculture management practices can significantly reduce the amount of nutrients, pesticides, and other crop inputs [38][39]. Catchment management focused on the introduction of cost-effective ecological agricultural systems and was supported by various measures aimed at lake revitalization that would provide the opportunity to restore the good ecological status of lakes in a relatively short period of time.…”

Performance of Wheat (Triticum aestivum L.) under Need based Nitrogen Management Strategies and Different Tillage Options

“…Increment of N use efficiency can be obtained only when the application will coincide with most hungry stages with adequate amount that reduce the losses (Diacono et al, 2013). From sustainable point of view, the N management in wheat needs to be refined for improving N use efficiency, crop productivity and profitability, and minimizing fertilizer N loss to the environment.…”