The application of nitrogen (N) fertilizer is an important cultivation option to enhance profitable production in general, and especially in the Southeast Asian countries or other tropical countries. In some cases, large amounts of N remain in soils after the crops are harvested, leading to the deterioration of the groundwater quality through nitrate leaching and of air quality through nitrous oxide (N2O) emission. The purpose of the present study was to determine the effects of three types of controlled-release N fertilizers (CRFs) on: a) leafy vegetable growth, b) nitrate leaching from the surface (0-20cm) soil, and c) N2O flux in the soil surface. Komatsuna (Brassica campestrisL.) plants were grown in plastic containers filled with arable soil, and five treatments were applied as follows: application of CDU, UBF, UBM2 and urea fertilizers, and control (no N fertilizer) . Three types of CRFs and urea were applied at the rate of 150 kg N ha-1. The treatments with UBM2 and urea resulted in the highest values for the growth parameters and N uptake of Komatsuna plants. The amounts of total nitrate in the leachate were significantly higher in the UBM2 and UBF treatments than in the CDU and urea ones. The highest N2O emission from soil was observed in the CDU treatment, followed by UBF, UBM2, urea and the control. The nitrogen use efficiency was highest in the treatments with UBM2 and urea.
Na+ and K+ concentrations in different plant parts and some physiological features under NaCl solution treatment were investigated to study the absorption and distribution of Na+ and K+ inMetroxylon warburgii (Heim) Becc. that belongs to same genus with sago palm (M. saguRottb.) in the palm family. Seedlings at the 11th or 13th leaf stage were used for the treatment of 342mM (2%) NaCl in a green house under natural sun light in mid summer in central Japan.M. warburgiimaintained a low Na+ concentration in the leaflets of upper active leaves by storing Na+ mainly in the petioles at lower leaf positions under the NaCl treatment for 36 days. The Na+ concentrations in the roots were lower in the steles than in cortices, and this result suggests the existence of a mechanism to restrict the over influx of Na+ from the cortex into the stele of the roots. The K+ distribution to the leaflets was not affected by the change in the Na+ concentration in the roots and petioles inM warubrugii. Photosynthetic rate decreased with the NaCl treatment, which was attributed to decrease in stomatal conductance and chlorophyll content per unit leaf area.
Sandy soils are generally unfertile, but limited information is available on the soil-plant nutrient dynamics. To examine the relationship between the nutrient contents in soil and growth, yield and nutrient uptake by plant and to propose rational practices for sustainable agricultural system, maize was cultivated in 2004 on a sandy soil in Khon Kaen, northeast Thailand. Six treatments were applied: NPK (100kg ha-1), PK, NK, NP, control and NPK+manure treatments. Soil samples were collected and available and total contents of NPK determined. Plants were harvested and the dry weight, yield and NPK contents determined. The amounts of available N, P and K within lm of soil were 47, 261 and 256 kg ha-1, or 2.2, 7.3 and 1.8% of the total, respectively. About 37% of available N and 50% of available P were stored within the surface 20cm, where more than 80% of the roots distributed. Aboveground biomass in the PK, NK, NP and NPK treatments were 4, 25, 79 and 98% higher than the control (3.71 t ha-1), respectively, indicating that N was the dominant limiting factor, followed by P and K. In conclusion, adequate N and P fertilization and erosion control would be essential for sustainable agricultural system for maize.
The effects on the growth and yield of bitter gourd of an energy-saving hydroponic system consisting of coconut coir media, in which power-driven circulation of a nutrient solution was not installed were investigated using full (standard) and half strength commercial nutrient solutions, compared with rockwool media. The changes in the nutrient concentrations in the growth media, chemical characteristics such as fixation (adsorption) or release of nutrients by/from the media and physical characteristics were also examined. The vegetative growth of the plants was not affected by the media or the strength of the nutrient solution. The yield of marketable fruits per plant was higher with the use of a half-strength nutrient solution in the coconut coir media than with that of a half-strength solution in the rockwool media. Fruit number per plant was lower with the use of a half-strength nutrient solution in the coconut coir media than with that of a full strength solution. The fruit quality (fruit length) was not affected by the strength of the nutrient solution. The concentrations of all the mineral nutrients of the coconut coir media supplied with a full strength solution showed a five to nine fold increase, compared with those in the nutrient solution supplied at the time of vigorous plant growth. Although the potassium concentration in the coconut coir supplied with the half-strength solution showed a two fold increase, the concentrations of nitrogen and phosphorus decreased. Release of potassium from the coconut coir media was confirmed in the laboratory experiment. The nutrient concentrations of the leaves were higher than those reported for the leaves of the plants cultured in soil, except for the concentration of nitrogen. Thus, we concluded that the use of a half-strength nutrient solution was suitable for the energy-saving hydroponic system in bitter gourd cultivation. However, for continuous reuse of the coconut coir media, further trials should be conducted to maintain stable levels of nutrients and to re-adjust the nutrient concentrations in the media.
To develop a marketing system for the supply of atemoya‘Jeffner’fruits from winter to spring seasons, the effects of the rootstock and time of summer pruning on shoot growth, fruit quality and yield were investigated. Suitable rootstocks and pruning times for the cultural environment in Okinawa prefecture were evaluated. The length and basal diameter of the shoots were significantly affected by the rootstock and pruning times. The later the pruning time, the lower the value of the shoot length and basal diameter. When sugar apple rootstocks were used, shoot growth of the scion was less vigorous, compared with the use of cherimoya and atemoya rootstocks. Flower formation was not different between the rootstocks, and the number of flowers decreased with the delay in the pruning time. Flower buds that emerged after pruning in October died. Rootstock did not affect the fruit weight, fruit shape and number of seeds per fruit. Brix value of the fruits was lower on vigorous cherimoya and atemoya rootstocks compared with that on weak sugar apple rootstocks. Pruning in August increased the Brix value, compared with pruning in July. The fruit yield was higher on sugar apple and cherimoya rootstocks, and the fruit quality was higher on the former rootstock, while tree growth became more vigorous on the latter one. Pruning should be completed by September for fruit production.