Productivity of irrigated pastures following paraplowing and gypsum slotting of subsoil exposed by laser landforming dash a short term study

Abstract

The effect of two soil amelioration techniques (paraplow and gypsum-enriched slots) on the productivity of white clover/ryegrass pasture was assessed by monitoring plant and soil water status and canopy gasexchange during an irrigation cycle. The soil was a dense clay, exposed when the topsoil was removed during laser landforming. Pasture growth on such exposed subsoils is very slow.All parameters of soil and plant water status indicated that there was some benefit from amelioration, with slots > paraplow > control. This trend was reflected in canopy photosynthesis. The photosynthetic efficiencies of canopies declined rapidly after 40 mm Class A pan evaporation less rainfall (E- R) in the control and after 50 mm E - R in the paraplowed treatments. At the end of the irrigation cycle (72 mm E - R) the efficiencies of the control and paraplow were about 20% and 50%, respectively, of the wellwatered. The efficiency of the canopy in the slot treatment remained high throughout.Without soil amelioration, pastures grown on exposed subsoil cannot maintain high levels of photosynthesis during a normal irrigation cycle in summer. More frequent irrigation or soil amelioration (or both) are required if pasture production on exposed subsoil is to be dramatically improved.