Improved canopy and N management for the GB potato crop

A nitrogen management model that describes total N uptake and the redistribution of N from haulm to tubers as a function of the quantity of radiation absorbed by the crop has been developed through AHDB Potatoes funding. The model can be used as a canopy management tool and its successful implementation allows growers to “design” their own crop canopy to maximise nutrient use over the season, so that wastage of applied nitrogen is minimised.

The purpose of this project was to validate the principles underpinning the N model and to use it to interpret the growth and yield of experimental and commercial crops, as well as improving the understanding of varietal differences in N nutrition and fertilizer use efficiency. The validation showed that simple relationships with radiation absorption explained much of the variation in total and tuber N uptake by potato crops and that these simple relationships could then be used to make inferences about canopy persistence and yield potential. Differences in a variety’s response to N fertilizer can be explained by an understanding of how increasing the N supply affects total N uptake and the rate at which N is transferred from the haulm.  This understanding can be used to rank varieties in their response to N.

The study demonstrated the importance of total N uptake in determining canopy persistence and since most N uptake occurs within the first half of the growing season, yield potential is also determined early in the season.  This knowledge led to practical recommendations involving the timing of N applications.  Detailed measurements in commercial crops showed that, due to spatial heterogeneity of root systems in ridge planted potato crops, N falling into the wheeling is unlikely to be recovered efficiently.  Minimising the loss of basal and top-dressings of N into wheelings will increase N use efficiency and enable reductions in the overall N application rate.   

Several experiments tested the effects of poor soil conditions (e.g. compaction or cloddiness) on the N uptake and yield of crops.  In many of these experiments the effects of poor soil conditions on yield were small, but in all cases the effects were explicable in terms of the dynamics of N uptake and redistribution.  These experiments also showed that the yield penalty associated with poor soil conditions could not be removed by applying extra N (or water) but in those crops receiving no or small amounts of N, the effects of poor soil conditions tended to be more severe.

Experiments also showed that when compared to rain-fed crops, irrigation increased the apparent efficiency with which crops recovered both soil and fertilizer derived N.  This increase in efficiency showed why the larger yield associated with use of irrigation could be achieved without use of more N fertilizer.

To develop systems that will give growers better control of canopy and nitrogen management.