Americas and Oceania Group - International Plant Nutrition Institute

ut the two treatments did not differ much in the capture of water (ratio of ET/total precipitation). The EI
treatment also showed higher N use efficiency and N removal and less negative N balances, but lower partial
factor productivity of N as compared to the FP treatment. IPNI-24
Global Maize Project in Argentina: Oro Verde, Entre Ríos
Project Leader: Octavio Caviglia, Instituto Nacional de Tecnología, (INTA EEA Paraná), Oro Verde, Entre Ríos.
E-mail: ocaviglia@parana.inta.gov.ar
Project Cooperators: Ricardo Melchiori, Pedro Barbagelata, Carolina Sasal, Hugo Tassi, and Osvaldo Paparotti
A long-term field experiment has been established at Oro Verde (Entre Ríos) in the 2009/10 growing
season. The crop rotation is maize-wheat/double cropped-soybean, with both crop phases occurring each
year. Soil samples were collected during site establishment to characterize initial conditions, especially soil
carbon content in the whole soil profile. Treatments include current farmer practice (FP) and ecological
intensification practice (EI). Treatments differed in either cultivar, planting date, pest and weed control, or
nutrient management practices.
Maize yields showed an excellent response to the EI treatment with 5,787 and 9,287 kg/ha yields for the FP
and EI treatments, respectively—a significant difference of 60%. Wheat yields were affected by rust (Puccinia
triticiae) and were 3,792 and 3,249 kg/ha yields for FP and EI, respectively, with significant differences
between treatments. On the other hand, double cropped-soybean yields were similar for both treatments and
were 3,128 and 3,123 kg/ha under the FP and EI treatments, respectively.
Considering the first 2 years and the three crops involved in the maize/wheat/doublecropped soybean, the
EI treatment significantly improved water use efficiency (determined as kg grain per mm of ET) over FP, but
the treatments didn’t differ much in the capture of water (ratio of ET/total precipitation). The EI treatment
also showed higher N use efficiency and less negative N balances, but lower partial factor productivity of N
when compared with the FP treatment. IPNI-25
Uruguay
Exploration of Responses to Potassium in Western Uruguay
Project Leader: Monica Barbazan and Oswaldo Ernst, Universidad de la República Producción Vegetal Facultad de
Agronomía – EEAMAC, Paysandú, Paysandú. E-mail: oernst@fagro.edu.uy
Project Cooperators: Martin Bordoli, Carlos Bautes, Esteban Hoffman, Andres Quincke, Juan Diego Cano, and
Sebastian Mazzilli
This research is partly based on previous observations of K deficiency and responses in field crops grown
within the northwestern Uruguay region. Data from the first 3 years of field work and other studies, including
50 experiments under wheat, barley, maize, soybean, sunflower, or sorghum, indicated a critical range of
0.30 to 0.40 cmol/kg (117 to 156 ppm), below which there is a high probability of response to K fertilization.
Integration of soil survey data with this field work has allowed researchers to estimate that 4 million ha have
the potential for soil K deficiency in all Uruguay.
On-going field work in 2011-12 is evaluating the effects of K fertilization in winter crops (wheat and
barley) and double-cropped soybean. Three of nine experiments located in the traditional agriculture area
showed significant yield responses to K application in wheat or barley. Grain yield responses averaged 638,
152, and 220 kg/ha in sites with soil exchangeable levels of 0.24, 0.29, and 0.32 cmol/kg (94, 113, and 125
ppm). These experiments are being evaluated for residual effects on double-cropped soybean grain yields.
Field studies on the dynamics of K release from crop residues, have shown an increased release of K from
maize and soybean stover in the early days since residue deposition. The amount of K released was associated
with the type of crop and rainfall accumulation. The exchangeable K showed the highest variations in the first
3 cm deep, and was associated with the amount of K supplied by the residues.
Laboratory studies indicated that the K buffering capacity of different agricultural soils vary according to
clay content, soil organic matter, and exchangeable Ca and Mg concentrations. An average rate of 184 kg/
ha of applied K was needed to increase exchangeable K by 0.1 cmol/kg of exchangeable K in 36 agricultural
soils, with a range of 68 to 455 kg/ha. Uruguay-02 v
IPNI Interpretive Summaries 51