Reducing Phosphorus Fertilizer Input in High Phosphorus Soils for Sustainable Agriculture in the Mekong Delta, Vietnam

Abstract

High rates of phosphorus (P) currently being applied to soils for the production of vegetables in the Mekong Delta, Vietnam, has led to concern regarding negative effects on the economy and the environment. This research presents a comprehensive study on the determination of P supplying capacity in this region of Vietnam to examine the possibility of reducing P fertilizer input. In total, 120 soil samples were collected to evaluate total P and Bray 1 available P in the soils. Phosphorus maximum sorption, degree of P saturation, P release, and the effect of P fertilizer on corn (Zea mays L.) yield in greenhouses and fields were also determined. Total P concentrations in 57% of the soil samples evaluated yielded high P concentrations (>560 mg P/kg), while 74% of the samples had high Bray 1 available P concentrations (>20 mg P/kg soil). Maximum P sorption ranged from 149 to 555 mg P/kg soil, respectively, and had negative correlation with available P (r = −0.63*). The percentages of P saturation ranged from 0.63% to 5.5% and correlated with available P (r = 0.98**). Maximum P release ranged from 1.2 to 62 mg P/kg soil, respectively, and correlated with available P (r = 0.96**). Corn grown in soils with available P concentrations >15 mg P/kg did not respond to P fertilizer in greenhouse or field experiments. We conclude that many farmers in this region can reduce P fertilizer input, thus increasing their profits and reducing negative environmental impacts associated with excess soil P for sustainable agriculture.

Influence of Phosphorus Fertilizer on Maize Vegetable (Zea may L.) in Soil Southern Vietnam

“…In this experiment, due to low pH, phosphate fertilizer application at various doses did not increase the height and diameter of the plants. Similar results were found in P-rich soils in the Mekong Delta Vietnam by Thuy et al (2020).…”

Aplicação de Resíduos da Indústria Sucroalcooleira em Solo como Forma de Mitigar Impactos Ambientais

“…De acordo com Thuy et al (2020), teores de fósforo em níveis considerados adequados nos solos devem variar entre 21 a 30 mg dm -3 , necessitando, possivelmente, de maior dosagem de vinhaça para atingir esse nível recomendado. Outra possível causa para essa redução do teor de P no solo tenha sido a baixa solubilidade dos compostos de fósforo no solo e formação de compostos nãolábeis ou não reativos, ou seja, quando fontes solúveis de P, na forma de fertilizantes e resíduos orgânicos, são adicionadas ao solo, inibindo a assimilação desse elemento por parte das plantas, especialmente quando se trata da utilização de resíduos orgânicos como fonte de adubação (Araujo Filho et al, 2015).…”

“…Esses mesmos benefícios com a utilização da torta de filtro foram descritos por Mota et al (2019), onde verificaram, utilizando a cultura da cana-de-açúcar em condições de campo com Latossolo Vermelho distrófico, resposta da cultura à adubação com torta de filtro ao solo. De acordo com as classes de fertilidade de solo proposta por Thuy et al (2020), os teores de P do solo foram classificados como níveis alto acima de 10 mg kg -1 . Os resultados obtidos neste estudo fornecem um indicativo do potencial da torta de filtro como fonte fosfatada.…”

Refining phosphorus fertilizer recommendations based on buffering capacity of soils from southern Brazil

“…In soils with insufficient P availability, the addition of phosphate fertilizers improves the nutrient use efficiency (Cubilla et al, 2007;Rubio et al, 2008;Reis et al, 2020). The saturation of the adsorption sites with the highest binding energy (Rheinheimer et al, 2003;Oliveira et al, 2014), and the increase in the number of negative electrical charges (Barrow, 2015), reduce the P adsorption, allowing a greater percentual of P available to plants ( Barrow and Debnath, 2018;Boitt et al, 2018;Zhang et al, 2018;Thuy et al, 2020). Thus, in corrected soils, the phosphate fertilization has higher efficiency of use by plants, and less amount is needed to meet plant's demand (Barrow and Debnath, 2018;Withers et al, 2018).…”