Min-Jin Lee

Partitioning of N-uptake from 1-year of fertigation with 15N-urea in pot-lysimeter-grown M.9-grafted apple trees after 3 years of fertigation with unlabelled urea at three rates of N

Summary The total amounts of N derived from 15N-urea in the organs of 18 newly-bearing “maiden” apple trees and in the soil were determined after 1-year of fertigation with 15N-urea by drip irrigation, scheduled at a soil matric potential of –50 kPa. Prior to this treatment, the 18 “maiden” apple trees had been fertigated with three concentrations of N for 3 years: 17 mg N l–1 (low), 34 mg N l–1 (medium), or 67 mg N l–1 (high), and the same rates of 15N were chosen for treatment comparisons over the following 1 year. The trees were fertiligated with an aqueous stock solution of 15N-labelled urea (1.5 atom % 15N), KH2PO4, and KCl by drip irrigation. The phosphorus (P) and potassium (K) concentrations were constant, and set at 17 mg l–1 and 34 mg l–1, respectively. The total irrigation volume applied per tree was 363 l for the low, 430 l for the medium, and 216 l for the high N treatment.The corresponding supplies of N per tree were 6.17, 14.62, and 14.47 g, respectively. The total amounts of urea-N absorbed per tree were 1.90 g for the low-N, 3.73 g for the medium-N, and 3.21 g for the high-N treatments, with the percentage of N recovery (30.8%, 25.5%, and 22.1%) decreasing with increasing N rate, while the N retained in the soil was 2.92 g (47.3%), 7.40 g (50.6%), and 8.35 g (55.7%), respectively. Fertiliser N contributed more to whole-tree N uptake at increasing rates of N than N uptake from the soil. The total recovery of 15N from each tree-soil system was 78.1% at the low, 76.1% at the medium, and 79.8% at the high N level, with an average of approx. 22.0% of N unaccounted-for. The total amounts of P and K taken up were 2.42 g tree–1 and 14.49 g tree–1 for the low-N, 2.47 g tree–1 and 15.33 g tree–1 for the medium-N, and 1.31 g tree–1 and 8.04 g tree–1 for the high-N treatments, respectively. Our results showed that an N concentration of 34 mg l–1 (medium) resulted in more productive and profitable trees, bearing more fruit of higher quality than the other two N treatments. This concentration of N also improved the development of new leaves and flowers during the early stages of growth in the following Spring.

Variation Patterns in Concentration of Inorganic Nitrogen from Liquid Grass Fertilizer during Aerobic Incubation

To assess fertilizer value of an quasi-aerobically fermented liquid clipped-grass fertilizer, aerobic incubation experiment using two texturally contrasting loam (L) and sandy loam (SL) soils was conducted for 60 days to investigate temporal variations in N mineralization pattern of the liquid fertilizer applied. To do so, the quasi-aerobically fermented liquid clipped-grass fertilizer was prepared, applied to each soil at a rate of 200 kg-N and aerobically in the dark. During incubation, soil water content was adjusted to field moisture capacity (-33 kPa of soil matric potential) by adding distilled water as necessary to maintain their initial weights. At desired time of incubation (0, 1, 5, 10, 20, 40, and 60 days after incubation), soil was sampled and analyzed for inorganic nitrogen (-N and -N) concentrations, pH, EC, total carbon contents and total nitrogen contents. Concentrations of -N began to decrease right after incubation for L soils, and 10 days after incubation for SL soils, while those of -N began to increase onset of -N disappearance. The results of this study showed that quasi-aerobically fermented liquid clipped-grass fertilizer could serve as an alternative to chemical N fertilizer.

Effect of Mixed Liquid Fertilization on Growth Responses of Red peppers and Soil Chemical Properties

We evaluated the effect of mixed liquid fertilizer (MLF) on growth responses of plants and soil chemical properties. A pot experiment with red pepper (Capsicum annuum L.) using loam soil was conducted for 81 days in a temperature-controlled glasshouse, and four N fertilization treatments were laid out in a completely randomized design with three replicates: control (C), chemical fertilizer treatment (CF), and two rates (MLF-0.5 and MLF-1.0) of MLF treatment. Soils were periodically sampled and analyzed for pH, EC(Electrical Conductivity), total N, inorganic N and total C, and some growth characteristics of red peppers were measured. During the experimental periods, the pH of MLF soils was higher than that of CF soils. Soil EC increased right after application of CF or MLF, and the intial increase persisted in CF and MLF soils at the end of experiment. Soil total-N increased right after application of CF or MLF, and this initial increase persisted only in MLF-1.0 soils. Soil inorganic N content initially increased in CF or MLF-1.0 soils, but the initial increase disappeared in 56 days after transplanting. Soil total-C was maintained higher in MLF-1.0 soils and lower in CF soils than in control soils, and the intial increase in MLF-1.0 soils finally disappeared to the level of control soils. Plant height, dry weight of plant organs (shoots, roots and fruit), and the number, diameter and length of red pepper fruits were greatest in CF plants. On the other hand, the effect of MLF-application was different depending on the rate of application. However, no consistent effect of N treatments on some major elements of the organs of red peppers was observed. The amounts of N taken up by plants were 1.3 g for CF, 0.8 g for MLF-1.0, 0.5 g for MLF-0.5 and 0.4 g for control treatments. The results of this study showed that mixed liquid fertilizer (MLF) could appropriately serve as an alternative to chemical N fertilizer in red pepper cultivation.