research update


Everything in


PARC study links blueberry success tomoderate irrigation and applying nitrogen through fertigation.


By Tamara Leigh M


ore is not always better, and results fromtwo studies on irrigation and fertigation are helping farmers find the right balance in


applyingwater and nitrogen fertilizer to blueberry crops. Dr.David Ehret andDr. TomForge fromthe Pacific


Agri-FoodResearch Centre (PARC) in Agassiz have been collecting data on their plots since 2008 to understand the effects of drip irrigation on production and fruit quality, and to find themost effective rate andmethod of nitrogen application. “Currently,most blueberry growers in B.C. irrigate


via drip irrigation, but do sowithout really knowing howmuch to apply andwhen to apply it. In short, they guess,” says Ehret, the lead on the irrigation study. “The effects of irrigation on the crop are also not fully understood.What are the effects on yield and fruit quality?Does over-watering increase root disease? The study is trying to address some of those questions.” The irrigation study set up nine treatmentswith a


combination of lines, emitters and volumes.Non- irrigated plots received nowater,moderate irrigation received 70,000-80,000 litres per hectare, and heavy irrigation received 140,000 to 1.6million litres per hectare. In terms of the irrigation systemdesign, the


BRENDA FREY


Irrigation study plots at the Pacific Agri-food Research Centre, Agassiz.


Moderate irrigation rates also showed themost Ehret


promising resultswith fruit quality indicators including fruit size, firmness and sugars. Berry size increased from216 grams per 100 berries in the non-irrigated plots to 221 grams per


100 berries in themoderate and heavy irrigation plots. The benefits of bigger berries are offset by losses in firmness and fruit sugars as the amount of water increased. “It’s not advisable to over-irrigate,” says Ehret.


“Fruit firmnesswas progressively decreasedwith increasing irrigation, so the least firmfruitwere fromthe heavy irrigation treatment. Similarly, the sugar content decreasedwith irrigation.” Results of the PARC nitrogenmanagement study


Forge


number of lines and emitter spacing had no effect on production or fruit quality. “Itmay be that the roots are simply growingwhere thewater


is, irrespective of howmany lines or howclose the emitters are as long as the volume applied is the same,” explained Ehret. The study found that increasing rates of irrigation increases


production butwith diminishing returns.Over five years, the cumulative yields sawa 13 percent increase in productionwith moderate irrigation, and only three percentmorewith heavy irrigation, using twice thewater. Thiswas further reflected in thewater use efficiency of the different plots. As they reached maturity, themoderate irrigation plots produced 3.6 kg of fruit per 1,000 L ofwater applied, compared to 2.6 kg of fruit per 1000 L ofwater in the heavy irrigation plots.


12 British Columbia Berry Grower • Winter 2013-14


are showing the benefits of optimizing the rate and method of application of this important nutrient. “Grower production guides often recommend


rates of nitrogen application to producemaximumyield, but we alsowanted to find out howvarious nitrogen rates affected fruit quality,” says Ehret. “We alsowanted to find out if the method of application of nitrogenwas important. Broadcast is the conventionalmethod, but fertigation is increasing in popularity, sowe compared the two.” The study established treatmentswith no nitrogen


application, broadcast application at three rates (50 percent, 100 percent and 150 percent of production guide) and fertigation application at three rates. In broadcast treatments, nitrogenwas applied three timeswith one-third of the total applied at each date. The fertigation treatmentswere applied 10 timeswith one-tenth of the total applied at each date. Overall, results showthat berry production goes upwith


moderation


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