In Situ Monitoring of a Controlled Release of Fertilizers in Lettuce Crop

Abstract

Agriculture has sought ways to increase food production to meet global demands, intensifying dependence on natural resources. An alternative for intensive production has relied on the use of "smart" fertilizers that release nutrients in a controlled manner. Biodegradable polymers containing fertilizers has presented economic and environmental advantages when applied to the soil, as they release water and nutrients gradually to the environment without leaving residues. The objective of this study was to monitor the behavior of chitosan-clay hybrid microspheres, used as potassium nitrate soil ferti-releaser in lettuce cultivation. The experiment consisted of two treatments: (i) application of ferti-releasing chitosan-clay microspheres and (ii) use of conventional fertilization. Both treatments were monitored with TDR probes to measure electrical conductivity and soil moisture. The results indicate that both moisture and electrical conductivity are higher in soils treated with the ferti-releasing material. In addition, there was a gradual and homogenous release if compared to the conventional fertilization. The statistical analysis showed that the microspheres were efficient mainly for the controlled nitrogen release.

Influence of organic mulching on drip irrigation management of cabbage cultivation

“…TDR probe provided the apparent dielectric constant (Ka) of soil, which was replaced in Equation 2 (Souza et al, 2017), obtained from the calibration for this soil. = 0.000005 3 − 0.0003 2 + 0.0161 1 + 0.0132…”

“…14 n. 4, e2381 - Taubaté 2019 2017 TDR probe also provided values of soil electrical conductivity. However, Equation 4 (Souza et al, 2017) was necessary to suit the soil used. = 0.0303 + (4.602 × ) − (0.7 × )…”

“…Where: EC -soil electrical conductivity (dS m -1 ); ECTDR -electrical conductivity provided by TDR (dS m -1 ); θ -soil moisture obtained with Souza et al (2017) equation.…”

Deficit Irrigation of Subsurface Drip-Irrigated Grape Tomato

“…The values of the apparent dielectric constant of soil (Ka, dimensionless) were converted into soil volumetric moisture (θ, m 3 m −3 ) according to [eq. 1] (Souza et al, 2017). Readings were performed three times a week and the means of each treatment were considered in the reading of the day.…”

“…θ = 5e-6 × Ka 3 -3e-4 × Ka 2 + 0.0161 × Ka + 0.0132 1TDR probes also provided the apparent electrical conductivity of soil (ECTDR, dS m −1 ), which was estimated by [eq. (2)] for the electrical conductivity (EC, dS m −1 ) adjustment regarding the saturated paste (Souza et al, 2017).…”