No abstract

Balanced nutrients are essential for healthy plant growth, but there is no sensor available to monitor essential nutrients such as N and K. Electrical conductivity (EC) is one of the key parameters that could be adopted to monitor these nutrient contents because soil EC is influenced by available nutrients. Therefore, the main objective of this study was to examine the effects of different basal fertilizers including inorganic, organic, and compost fertilizers, and the application ratio of basal and additional fertilizers on nutrient contents by EC sensor. The applied basal and additional fertilizer ratios were N 30:70, K 40:60, and N 20:80, K 20:80, respectively, for each fertilizer treatment. EC sensor value was positively associated with water content. Soil EC response increased with the application of inorganic fertilizer and fertigation and was positively correlated with soluble nutrients and exchangeable ammonium. The principal component analysis also determined that inorganic fertilizer was positively associated with sensor EC, soluble Na, Ca, Mg, and nitrate among the variables. This work suggested that soil available nutrients especially N can be monitored by an EC sensor which can be used to control soil nutrient status for better plant growth.

Plant-induced electrical signals (PIES) can be non-destructively monitored by inserting electrodes into plant stems, which reflect plant nutrient and water uptake. The main objective of this study was to evaluate the growth of pepper plants with different urea applications (low fertilizer: N0, Control: N1, and high fertilizer: N2) in soil by monitoring PIES. The PIES value was found to be low in the low urea treatment group while the two times higher urea applied pepper had the highest PIES value. The nutritional content of the stem, leaves and soil did not correlate with PIES because of dilution effect by high biomass with high urea application, but principal component analysis showed that the PIES was positively associated with pepper biomass and soil EC. The high fertilizer did not affect chlorophyll and proline contents in pepper leaves. The assessment of plant growth by PIES has advantages because non-destructive, real time and remote monitoring is possible. Therefore, PIES monitoring of different plants grown under various cultivation environments is useful method to evaluate plant activity and growth.