Impact of Cropping Sequence and Tillage System on Response to P Fertilization in Durum Wheat and Soybean

A study done to improve our ability to predict when P starter fertilizer is required by crops and identify management practices and fertilizer sources that may improve early season P availability to crops.


30 Jan 2008

2007 Annual Interpretive Summary

Impact of Cropping Sequence and Phosphorus Fertilization on Cadmium and Zinc Accumulation in Soybean and Durum Wheat, 2007

Crop sequence and tillage system can influence nutrient availability and response of crops to fertilizer applications, through effects on nutrient cycling, microbial population, soil temperature, and root growth. Therefore, optimum P fertilizer management may change with management practices as well as with crop type sequence. This study is evaluating the effects of cropping sequence and tillage practices on yield and quality response of durum wheat and soybean to different forms and placements of P fertilizer.

Phosphorus fertilization has previously increased the biomass yield in durum wheat, but not in soybean. When averaged over the 3 years of the study, wheat on both the clay-loam and silty-clay soils produced the highest grain yield when grown after canola and the lowest yield when grown after barley. On the clay-loam soil, P fertilizer produced a significant increase in yield. Durum wheat yield tended to be higher when ammonium polyphosphate was side-banded rather than surface dribble-banded, but was similar with monoammonium phosphate (MAP), ammonium polyphosphate, MAP treated with Avail®, and polymer coated MAP when the fertilizers were side banded. Cadmium (Cd) content of the durum wheat seed was strongly affected by preceding crop, being highest when grown after canola and lowest when grown after barley. Mycorrhizal colonization in durum wheat was not affected by P fertilization, but is highest when durum wheat has grown under reduced tillage following flax, and lowest when grown under conventional tillage following canola. It is possible that the increased mycorrhizal colonization due to the combination of reduced tillage after flax may encourage nutrient uptake and improve crop performance. There has also been an interaction between tillage system and preceding crop on biomass and grain yield. Generally, both soybean and durum wheat produced higher yields after flax than after canola under reduced tillage, but produced lower yields after flax than canola or barley under conventional tillage. Analysis of crop and soil samples is on-going from the 2007 crop year and will help clarify some of the factors causing the tillage system x previous crop sequence interaction. MB-20F