Sustainable irrigation and nitrogen management of fertigated vegetable crops

Abstract

Fertigation in combination with drip irrigation is being increasingly used in vegetable crop production. From a nutrient management perspective, this combination provides the technical capacity for precise nitrogen (N) nutrition, both spatially and temporally. With these systems, N and other nutrients can be spoon-fed to crops, through frequent applications of small amounts, to the immediate root zone as required by the crop. In commercial farming practice, management of combined drip/fertigation systems generally does not take advantage of this potential for precise N management. As is common in commercial farming, management of both irrigation and N with drip/fertigation systems is generally based on growers' experience, with the objective of avoiding deficiencies that may limit production. Because of frequent N application, the established improved nutrient management strategies, based on infrequent soil testing, pre-plant and one or two side-dress applications, are of limited value. With drip/fertigation, dynamic N management approaches are required so that the capacity for frequent small applications can be fully exploited to provide (a) site and season specific management and (b) dynamic responses to temporal N requirements. Dynamic irrigation management is required for the same reasons. Modelling and monitoring approaches and combinations of the two enable exploitation of the technical capacity for precise N and irrigation management. Decision support systems (DSS) based on simple simulation models with limited data inputs can provide crop specific plans of daily N and irrigation requirements. The use of soil moisture sensors is an effective and proven monitoring approach for irrigation management. For monitoring of soil/crop N status, soil monitoring through regular sampling of soil-water extracts and soil solution is being used, and crop/plant monitoring approaches such as with proximal optical sensors and petiole sap analysis are promising methods.

Proximal Optical Sensors for Nitrogen Management of Vegetable Crops: A Review

“…For optimal crop N management that ensures high production, while minimizing N losses to the environment, N fertilizer should be applied to match crop demand and to take into account N supplied by other sources, such as soil mineral N present at planting, and N mineralized from soil organic N, manure, and crop residues [ 9 , 13 , 16 , 17 , 18 ]. Optimal N fertilization of vegetable crops, in respect to both quantity and timing, would benefit appreciably from an accurate assessment of crop N status i.e., whether the crop N supply has been deficient, adequate, or excessive, and the degree of deficiency or excess.…”

“…Although these procedures are useful, in particular the soil analysis based recommendation schemes for estimating total requirements, the analyses are time-consuming and do not yield results quickly in the field so as to make fertilizer recommendations on time [ 21 ]. This is particularly so for vegetable crops that receive frequent N application through fertigation, which is being increasingly used with intensive vegetable production throughout the world [ 18 , 22 , 23 ]. With fertigated crops, ideal N management would involve rapid and frequent assessment of crop N status, enabling rapid adjustment of the N being applied [ 24 ].…”

New Trends in the Fertigation Management of Irrigated Vegetable Crops

“…Detailed laboratory analyses of soil samples are more useful for pre-transplant fertilization and for the evaluation of nutrient availability in the medium-long period, while for quick adjustments of fertigation during the cultivation cycle, the use of aqueous extracts appears to be more effective [100].…”

“…However, the most popular approach based on soil testing is probably the "Fertigation Model" [49] initially developed by Dutch researchers [117,119] before being used across Europe. The method has been extensively adopted at the commercial level in the Netherlands [100], and by growers from Mediterranean countries such as Italy [52] and Greece [128]. In Italy, the method can be applied with the user-friendly software GreenFert [52] (http://www.cespevi.it/softunipi/greenfert.html).…”

Soil Monitoring Methods to Assess Immediately Available Soil N for Fertigated Sweet Pepper

“…must ensure optimal, or at least considerably improved, crop N management. All growers have combined drip irrigation and fertigation systems that frequently apply small amounts of N [6,11,17]. Tools/systems that monitor crop N status or the immediate supply of crop available N will enable frequent N applications to be adjusted to ensure optimal crop N status [18,19].…”