Submitted Date: July 14, 2014

e-mail: tam.hv@iasvn.org

ABSTRACT

Dong Nam Bo (DNB) (South-eastern Region) is considered as one of the most favorable areas in the country to promote desirable crops, which are intensively grown for export purpose. Rubber, coffee, black pepper, cashew nut, maize, groundnut, and vegetable have been developed successfully. However, the unfavorable conditions, which have often threaten the production there, could be listed as soil degradation under tropical weather, poor soil organic content, and other factors. They significantly contribute to fast mineralization, unsustainable intensification. In addition, chemical fertilizer misuses or overuses have severely enhanced the worse situation. Practically, the bad thing is occurring in the Acrisols, which account for 30% of the DNB total arable areas. Acrisols in Vietnam occupied 19,970,642 ha, largely distributed in mountainous, mid-land, and plain sourrounding regions. It is divided into 05 soil units, including low humic gley soils with the largest areas especially various economic-value crops growing .

Study Objectives

• - To evaluate the impact of some commercial organic fertilizers on soil physical and chemical properties of DNB Acrisols.
• - To address the effect of some commercial organic fertilizers on productivity of short-duration genotype crops under DNB Acrisols conditions, then to evaluate their ability how to partly replace chemical fertilizer dosage.

Scientific and practical values

• - Scientific value: the result would evaluate the impact of organic mechanism of the recommended products to crop nutritional absorption and soil fertility. Then it can be contribute to the theoretical points how to propose the organic amendment solutions in Acrisols, to obtain soil fertility management, especially in the south-eastern region of Vietnam.
• - Practical value: the result would be a reasonable recommendation on organic application with some current commercial products. This would help reduce the chemical fertilizer overuse, protect our environment to gain the sustainable agricultural development.+

Processed organic fertilizers can completely replace conventional organic products. They can undertake their new function for market economy demand in agriculture. Their advantages were addressed in the study as economical effectiveness, soil fertility improvement.

At the organic fertilizer dose of  2.54–10.24 g HC/kg soil, the adsorption of N, P, K under haplic acrisols condition of southeastern region positively increased to the organic amount applied as 8.2-20.7% for N-NH₄⁺, 4.92-15.54% for P and 5.57-21.86% for K compared to check (without organic application).

At the same dose of processed organic fertilizers, the acrisols fertility properties were well improved as increased field capacity, water use efficiency, increased C-OM and better C-AH quality; improved CEC 0.27-0.54 Cmol⁺/kg soil, equivalent 2.53–8.53% as compared to check (without organic treatment). Soil microorganism community as N fixation, P degradation, cellulose degradation increased after organic treatment. However, pH tended to reduce properly, it needs to adjust on time.

Processed organic fertilizers increased the N, P, K releasing in grey soils of southeastern regions in case of maize. As compared to NPK treatment only, the organic application ones with 2.56 – 10.24 g HC/kg soil enhanced the absorbed N from 0.053–0.224g/pot (equivalent 19.13–62.81%); the absorbed P from 0.007–0.027g/pot (equivalent 18.42–71.05%); the absorbed K from 0.040–0.142 g/pot (equivalent 14.49–51.45%).

Processed organic fertilizer application (e.g. HCK, HCVS) in case of leaf vegetable, maize, groundnut growing in haplic acrisols enhanced crop productivity, reduced production cost due to NPK fertilizer input.

Economic effectiveness on leaf vegetable: Through 07 continuous seasons, at the dose of 3,000 kg/ha/season in case of Growmore (5-5-5) amd Humix (6-2-2), leaf vegetable overyielded 9.22 t/ha (equivalent 50.66%); and 8.34 t/ha (equivalent 45,82%), respectively, as compared to NPK treatment only. So Growmore (5-5-5) and Humix (6-2-2) can be fully replacing NPK treatments, or farm manure with 3 times reduced to assure high productivity of leaf vegetable.

Economic effectiveness on groundnut: Through two continuous seasons, at the HCVS dose of  500–2,000 kg/ha /season plus NPK treatment to have the same nutrion level of NPK treatment only, groundnut overyielded 0.43–0.94 t/ha/season (equivalent 15.69–34.31% as compared to check. The most efficient input was 500–1,500 kg/ha/season. At the HCK dose of 1,000-1,800 kg/ ha/ season, groundnut overyielded  6.00 –29.33% as compared to check.

Economic effectiveness on maize: Through two continuous seasons, at the HCCB dose of 750 –3,000 kg/ha/season plus NPK treatment to have the same nutrion level of NPK treatment only, maize overyielded 0.62–1.92 t/ha/season (equivalent 11.31–35.03%) and 0,50–1,65 t/ha/season (equivalent 9.10-30.00%) in case of HCVS and HCK, respectively. The most efficient input was 750-2,800 kg/ha/season and 720-2,200 kg/ha/season in case of HCVS and HCK, respectively.