Can within field yield variation be explained using horizontal penetrometer resistance and electrical conductivity measurements? Results from three Swedish fields

Spatial variations in yield occur in all agricultural fields to some degree. Knowledge of the reasons for these variations, especially temporally stable yield patterns, is needed in order to improve productivity by changing production methods or inputs. This information must be provided in a simple, cost-effective way. This study investigated whether field-scale measurements of penetration resistance (PR) could identify temporally stable yield patterns without complementary measurements of other properties. The PR measurements were also compared with field-scale apparent electrical conductivity (ECa) measurements and correlations between yield and PR and yield and ECa were investigated. Measurements with a newly constructed horizontal penetrometer and a non-invasive proximal electromagnetic induction sensor were carried out in three fields in east-central Sweden. The measurements were made once in each field, apart from one field where PR was measured twice in one season. The sensor measurements were compared with crop yield measured over the course of several years. The horizontal penetrometer was able to identify low-yielding areas in one field. However, single measurements of PR or ECa were insufficient to consistently identify yield variations. Parts of the fields showed more consistent patterns, with stronger correlations between PR, ECa and yield. PR and ECa data were better at explaining yield variations in drier years, but showed diverging patterns in different fields and neither showed a much stronger correlation to yield than the other. In future studies, simultaneous measurement of soil water content is recommended and also PR measurements at a water content drier than field capacity.     

Effect of gypsum on exchangeable sodium percentage and electrical conductivity in the Daeho reclaimed tidal land soil in Korea—a field scale study

Purpose

A reclaimed tidal land along the shore has poor soil properties such as high exchangeable sodium percentage (ESP), and electrical conductivity (EC) due to excess sodium (Na) content. Therefore, Na content should be decreased to improve the land productivity, and for this, gypsum has been widely used. The objective of this study was to determine the changes in ESP and EC of the gypsum-treated reclaimed tidal soil in a field scale.

Materials and methods

For this, gypsum was applied to Daeho reclaimed tidal land (500 ha) in Korea for 5 years (2006 to 2010). The Daeho reclaimed tidal land has been used as reclaimed paddy fields since 1993. The application rate of gypsum was calculated based on exchangeable calcium (Ca) contents and soil cation exchange capacity (CEC) to maintain 60 % exchangeable calcium percentage (ECP) of CEC in soil and the average amount treated was 1570 kg ha^?1 year^?1. The changes in ESP and EC were monitored from 2006 to 2010, and 2013.

Results and discussion

The ESP dropped from 80 % in 2006 to 34 % in 2013. The EC of the soil was decreased by 73 %, from 11.5 dS m^?1 in 2006 to 3.1 dS m^?1 in 2013. Eventually, it was estimated that the ESP will be lowered below 15 % in 2023 with continuous treatment of gypsum according to ECP calculation, and EC will be declined to reach at 0.5 dS m^?1 in 2035, the average EC level of Korean rice paddy.

Conclusions

This field scale study evidenced that gypsum application effectively improves the soil properties of reclaimed tidal soil by decreasing ESP and EC.