Epsilon Archive for Student Projects

Abstract

Catch crops have been found to decrease leaching of nitrates into surface and ground
waters, but they also have the potential to increase phosphorus (P) loadings to natural
waters as well, due to plant cell destruction caused during natural freezing and thawing
events. An indoor lysimeter experiment was carried out using a clay and a sand soil with the
application of four different plant species: perennial ryegrass cultivar ‘Helmer’ (Lolium
perenne L.), honey herb, cultivar ‘Stala’ (Phacelia tanacetifolia L.), chicory, cultivar ‘Puna’
(Cichoium intybis L.), and oilseed radish, cultivar ‘Adios’ (Raphanus sativus L.). These plants
were exposed to four simulated rainfall and three freezing events in two separate
experiments, one using topsoil monoliths with applied plant material and one with plant
material only. Sand and clay soils had significantly different leaching loads after 1 and 2
freezing events with total P contents in leachate equivalent to 0.71 kg ha‐1 for clay and 0.20
kg ha‐1 (P=0.0018) for sand soil, and after the second event 0.54 kg ha‐1 for clay and 0.30 kg
ha‐1 for sand (P=0.0026). The combined total P leaching loads from the clay soil were
significant for many of the plants and were in the order of chicory (2.6 kg ha‐1) > ryegrass
(2.3 kg ha‐1) > oilseed radish (2.2 kg ha‐1) > honey herb (1.3kgha‐1), taken from the plant and
soil experiment. Losses were of a magnitude greater from the plant only experiment with
chicory (51.7 kg ha‐1) > oilseed radish (43.2kgha‐1) > honey herb (18.4 kg ha‐1) > ryegrass (10
kg ha‐1). A total P analysis of plant tissue from before the first lysimeter experiment and after
the second plant only experiment showed that chicory lost 84%, oilseed radish 76%,
ryegrass 74% and honey herb 39% of total initial biomass P. The results indicate that soil
texture and plant choice can have a large impact on leaching loads that could potentially
enter natural waters.