Phosphorus Fertilizer Rate Based on PUTK Soil Analysis for Polyethylene Mulched Tomato Fertigation

Abstract

Implementing the precision farming system is one of the agricultural sector's adaptation strategies as the main food source in response to global climate change. Fertilizer recommendations in precision farming are based on soil nutrient content, so it is important to find the current soil nutrient content before applying fertilizer. From previous studies, correlation and calibration testing of available P and K analysis using PUTK on tomato plants has been carried out, so the next stage will be determining the recommended rate of P and K fertilizer for polyethylene mulched tomato plants. Three experiments were performed to determine recommendations for P fertilizer rate based on soil analysis using the Upland Soil Test Kit (PUTK) in cultivating tomato plants using a fertigation system. This experiment was carried out by testing the rate of P fertilizer on soil with low, medium, and high P availability based on soil analysis with PUTK. This study was carried out using a Randomized Complete Block Design (RCBD), four replications with one treatment, namely phosphorus fertilizer consisting of 0% X, 50% X, 100% X, 150% X, and 200% X, with X the recommended SP-36 fertilizer of each P availability status from PUTK. A higher P fertilizer rate in the low P availability experiment will increase tomato growth and yield but it is still linear. A higher P fertilizer rate in the high P availability experiment does not affect tomato growth and even lower yield. On the other hand, the P fertilizer rate treatment in the moderate P availability experiment didn’t affect tomato growth and production, because the experimental field used was considered to have high phosphorus availability based on the Mechlich 1 test (44,6ppm). Excessive fertilization will reduce crop yields and contribute to environmental degradation due to residual fertilizer accumulation. Therefore, applying fertilizers at optimal rates is essential to maximize production while ensuring environmental sustainability. PUTK is a rapid soil testing tool that can help farmers determine the nutrient content available in the soil. However, the PUTK test results are still qualitative, so they cannot differentiate between soil with medium-high and medium-low nutrient content. In this study, the experimental field was found to have moderate P availability according to PUTK analysis, whereas laboratory analysis using Mehlich-1 indicated high P availability. This suggests that further development of PUTK is necessary, such as replacing the P extractant with Mehlich-1, which has demonstrated strong correlations with vegetable crop performance. Moreover, developing methods to quantify soil analysis results could significantly enhance support for precision agriculture in horticultural crops.