Nitrogen, irrigation, and alley management affects raspberry crop response and soil nitrogen and root-lesion nematode dynamics

Commercial raspberry production in the Fraser Valley of British Columbia includes the use of synthetic fertilizers and manures to ensure that plants have adequate nutrients, particularly nitrogen, to produce high yields of quality fruit. The application of nitrogen in excess of crop uptake can, however, result in nitrate leaching to groundwater. As well, nitrogen applications can have non-target effects on populations of pests that may have longer-term consequences for production. In an effort to improve raspberry nitrogen management practices, a field experiment was set up to assess the influences of different nitrogen fertilizer application rates, types of fertilizers (synthetic vs manure), methods of scheduling irrigation, and the presence or absence of between-row cover crops, on overall crop vigor, berry yields, nitrate in soil, and populations of root-lesion nematodes which are damaging soil-borne pests of raspberry roots. The results indicated that variation in nitrogen application rate and type of fertilizer (synthetic vs manure) had little effect on raspberry vigor or yields. This was attributed to a relatively high amount of nitrogen being made available to plants from sources other than the applied fertilizer, such as atmospheric deposition and soil organic matter. As well, large root-lesion nematode populations may have suppressed raspberry growth in fertilized plots. Scheduling irrigation based on weather rather than on a calendar basis reduced water use by about 50% without affecting crop performance. Similarly, the presence of a perennial grass between-row cover crop reduced nitrogen accumulation in soil without affecting crop performance. Taken together, these findings demonstrate that it is possible to adopt practices that reduce risks of nitrate leaching without impacting raspberry production.