New Papers on Soil Water and Soil Nitrogen in Tropical Agriculture Published

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The Tropical Agriculture Website of Dr. agr. Volker Kleinhenz features two new publications on the seasonal effects of soil water on soil nitrogen in tropical agriculture in rice-based environments of Southeast Asia. These papers are based on agronomic research with several vegetable crops year-round at the Asian Vegetable Research and Development Center (AVRDC) in Taiwan.

Tropical Agriculture @ VolkerKleinhenz.com

Tropical Agriculture

Tropical Agriculture - Dr. agr. Volker Kleinhenz

Besides his Curriculum vitae, a number of presentations developed during his employment for scientific, commercial and rural-development companies, and several packages of cultivation practices for different crops, the Tropical Agriculture Website of Dr. agr. Volker Kleinhenz covers his scientific publications. Two of these publications address the impacts of seasonally fluctuating soil moisture on soil contents of plant-available soil nitrogen. The paper on "Soil moisture, soil and crop nitrogen, and yield of vegetables in a seasonally wet-dry tropical lowland" was published in the journal "Plant Research and Development" while the article on "Crop and N management to improve environmentally sound vegetable production in tropical lowlands" was published in the "Thammasat International Journal of Science and Technology".

The agronomic article "Soil moisture, soil and crop nitrogen, and yield of vegetables in a seasonally wet-dry tropical lowland" published in "Plant Research and Development" covers agricultural research on soil moisture tension, soil and plant sap nitrogen, root length density distribution, and yield in four vegetables year-round in rice-based tropical southern Taiwan. Vegetables included vegetable soybean, Chinese cabbage, chili, and carrot. Soil nitrate accumulated during the dry season when evaporation exceeded precipitation. This could not be explained by release of nitrogen from the low soil organic matter alone. Release of nitrogen from clay-fixed or other soil fractions may be significant in soil environments which are kept under anaerobic (submerged) conditions during paddy rice cultivation. Fertilizer rates can be reduced and vegetables with a high capacity to absorb nitrogen should be grown during the dry season to protect nitrate from being lost with the onset of rainfall in the wet season. Soil moisture was high and soil nitrate low during the wet season. Nitrification of ammonium fertilizer was slower than in the dry season and nitrate disappeared quickly after rainfall. Overall, stresses caused by excessive soil moisture in the wet season and deficient soil moisture in the dry season limited vegetable growth apparently more than limited availability of soil nitrogen.

The crop management paper on "Crop and N management to improve environmentally sound vegetable production in tropical lowlands" published in the "Thammasat International Journal of Science and Technology" compares the crop-management technology of permanent high beds and the N-management technology "Nmin-reduced method" with standard practices (flat beds and standard N rates) for their potential to increase vegetable production and prevent loss of nitrogen. Flat beds were more flood-prone during the rainy season. Root systems of vegetables on those beds were restricted to the uppermost soil layer. Both factors limited the ability of vegetables to efficiently absorb available soil nitrogen. The unused extra nitrogen of the standard N rate, consequently, leached below the root-zone. Permanent high beds successfully alleviated the negative impacts of overwet soil conditions during the tropical rainy season. Root mass of vegetables was greater and more roots stretched below 20-cm soil depth. Available soil nitrogen was effectively absorbed and thereby leaching of nitrate prevented. While the "Nmin-reduced method" was successful on standard flat beds, this rate could not maintain the greater biomass potential of vegetables on high beds. Overall, crop management technologies which improve growth and productivity of vegetables in tropical lowlands have a more significant impact on increasing crop production and reducing loss of nitrogen than N management itself.

Besides providing an overview of his scientific publications, Volker's homepage includes a continuously updated Curriculum vitae. Besides his recent assignments as a referee for the premium international agricultural journal Scientia Horticulturae and the Journal of Agriculture and Rural Development in the Tropics and Subtropics (JARTS), it also includes his latest consultation on Supplier Quality Management.

These details are also available at Volker Kleinhenz's LinkedIn profile, his homepage at the Asian Institute of Technology (AIT) in Thailand and his Twitter account @VolkerKleinhenz.

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