Pollen of ‘Bengal’ and ‘Chakrapat’ lychee was stored under various temperature and humidity conditions supposing the storage conditions can be duplicated easily by private orchads. During the storage under refrigerator temperature (5ºC) with 30% RH (relative humidity) condition, the ‘Chakrapat’ pollen which had 65% pre-storage germination (PSG) indicated slowly decreasing germination to 40% within 8 weeks. The germination decreased more rapidly when the pollen was stored under room temperature (20ºC) with 50% RH condition. Whereas the pollen stored under drier condition (RH < 10%) at 5 or 20ºC showed moderate decrease to 35% germination within one week, although no subsequent reduction within 8 weeks was observed. Deep-freezer temperature (-40ºC) storage for one month showed high germination which was similar to PSG for both cultivars. ‘Chakrapat’ pollen (60% PSG) showed 30% germination after one-year storage under the temperature of freezer (-10ºC) or deep-freezer (-40ºC) condition. Lower PSG (< 50%) pollen showed larger reduction in germination than higher PSG (≥60%) pollen when freezed or refrigerated during storage. Temperature of deep-freezer (-40ºC) was optimal for several-week storage. As a practical method, however, temperature of 5ºC with 30% RH seemed to be facilitative. In order to store pollen for one year, temperatures -10 and -40ºC are most recommendable.
It has been reported in our previous study that certain minerals were leached from the soil when ammonium sulfate is applied in excess. However, the mechanism of mineral leaching is not known. The objective of this study is to investigate the mechanism behind the leaching of certain minerals when ammonium sulfate is applied in excess. Haplic Regosols (Dystric) and Haplic Acrisols of Okinawa Island were used in the study. Both soils were applied with three levels of ammonium sulfate: 0 μg/g soil (N-0), 84 μg/ g soil (N-1) and 336 μg/ g soil (N-4). The moisture content of the soil was adjusted to 50 % of the water holding capacity and incubated in the dark at 25 °C for one month. After the incubation, pH, EC, inorganic nitrogen and solubilized minerals of the incubated soils were measured. In both soils, the pH and EC decreased with the time, but increased with increasing quantity of ammonium sulfate. The degree of nitrification in both soils was different. In the Haplic Regosols (Dystric), NO3--N content increased with the increasing of the ammonium sulfate application rate and, indicating most of the ammonium from fertilizer was nitrified during the incubation period. However, NH4+-N was higher than NO3--N in Haplic Acrisols. In this case, low acidity of the Haplic Acrisols may have retarded the nitrification. Protons released during the nitrification of the fertilizer under Haplic Regosols (Dystric) was higher than that of Haplic Acrisols. Certain amount of or certain type of minerals were leached from both the soils when the rate of ammonium sulfate application was increased. In both the soils, part of the exchangeable Ca and K were leached with the increase in the rate of ammonium sulfate application. It can be suggested that the leaching of above mentioned minerals was promoted by the protons released during the nitrification of ammonium ion of the ammonium sulfate.