The time for vari­able rate seeding is now!

Vari­able rate seeding is not only about increasing yields and reducing costs. It is also about responding adequately to declining precip­i­ta­tion caused by climate change. A visit to French farmers and contrac­tors who are imple­menting this tech­nique provides some insights.

With an average yield of 11t/ha in 2021, French maize produc­tion beat all its previous records, mainly thanks to suffi­cient rain­fall that was well spread over the entire produc­tion period. Years that are less favourable, both climat­i­cally and econom­i­cally, are unfor­tu­nately likely in the future. Cereal producers, live­stock breeders, and now biogas producers, must adapt their prac­tices to stay compet­i­tive. Let’s take a look at how preci­sion agri­cul­ture, in partic­ular site-specific seeding, contributes to this objec­tive.

French maize in 3 figures

  • 3 million hectares culti­vated (crop No. 2 after wheat)
  • 50%: Crop­ping area is divided between fodder maize and grain maize (2% of the area is seed corn or sweet­corn)
  • 40% of French produc­tion is sold for export to the Euro­pean Union (primary exporting country in the EU)

Breeding and maize, doing well together

The produc­tivity of current vari­eties is increasing by 1.2% each year, ie, a gain of 0.10 to 0.14t/ha in grain maize, and 0.13 to 0.18t/ha in silage maize, according to a study conducted by Arvalis – Institut du Végétal (Plant Insti­tute). One of the maize plant’s char­ac­ter­is­tics is its very high produc­tivity, despite a low seed rate per hectare. More than 13 tonnes of grain can be obtained with less than 100,000 plants/ha. Current early vari­eties require 5,000 to 10,000 plants/ha less, compared to the vari­eties from the early 1990s.

Faced with fluc­tu­ating weather condi­tions, increasing input costs, and fewer protec­tive seed treat­ments, farmers remain in constant search of secu­rity. And given the variety within fields, it is not in their interest to reduce seed rates too far. “Reducing the seed rate tends to lower the yield: Even if beau­tiful ears develop and the plants look good, the number of kernels/m² harvested is lower,” warned Pierre Cougard, of the Agro­nomic Depart­ment of the Eureden Co-oper­a­tive in an inter­view with the news­paper Le Paysan Breton (The Breton Farmer).

Preci­sion maize produc­tion

In an ideal world, farmers need to use the right variety, seed rate and nutri­tion, at the right time and in the right place. The funda­men­tals remain: An adequate soil struc­ture, a well-prepared seedbed, and a well-main­tained drill. Preci­sion maize cultivation is taking over, through knowl­edge of in-field vari­a­tion, the estab­lish­ment of vari­able rate seed maps, and geolo­ca­tion with centimetre-preci­sion equip­ment guid­ance.

Where water reserves are low, plants will suffer from stress. Lower seeding rates will relieve the suffering maize plants, offering them more water per plant, because the popu­la­tion per m² is lower. This does not prevent farmers from increasing seed rates where growing condi­tions are good.

Opti­mising water resources is one of the chal­lenges that can be addressed by vari­able rate seeding.

Vari­able rate seeding with support from trained service providers

Co-oper­a­tives and agri­cul­tural merchants are now devel­oping agri-envi­ron­mental services to meet soci­etal expec­ta­tions of reducing agriculture’s impact on the envi­ron­ment and biodi­ver­sity. Preci­sion agri­cul­ture is the main­stay to reach these goals. Seed compa­nies have started using specific appli­ca­tions, such as Agrility® (LG Semences), FITser­vices® (Pioneer Semences), Climate Field­view® (Dekalb/Bayer-Agri), Xarvio™ (BASF), etc. With agri­cul­tural contrac­tors, they make up the trio of preci­sion farming: Seed producers, agri­cul­tural merchants, and users of preci­sion farming tech­nolo­gies.

In the Grand-Ouest (Western France), the Cléo Network, with more than 15 contractor members and 400 employees in total, is a pioneer in imple­menting preci­sion agri­cul­ture. Training in digital tools, shared field trial plant­ings, and piloting the latest gener­a­tion single-grain drills are part of Cléo’s roadmap. Contractor company Coulon, located at Bouère, shares some customer expe­ri­ences – mostly live­stock farmers – about vari­able rate maize seeding.

Promoters of vari­able rate seeding in Mayenne, the three part­ners of contractor Coulon: Jean-Louis Mary, Jérôme Coulon and Anthony Hardou.

Contractor company Coulon in a nutshell

  • 20 full-time emplyees
  • 5 sets of Monosem planters
  • 23 trac­tors, mainly John Deere brand (dealer: Ets Ches­neau Agri-Ouest)
  • 5 self-propelled forage harvesters
  • 7 combine harvesters
  • 2 Self-propelled sprayers
  • 7 muck spreaders
  • 2 large square and 4 round balers

Coulon’s first expe­ri­ence of preci­sion farming was applying vari­able rate nitrogen to cereals, based on N-Sensor data. “For vari­able rate maize seeding, things are more tech­nical; you need to have knowl­edge of the varying yield poten­tial within a field,” admits partner Jean-Louis Mary. “We started by compiling yield maps, using the JDLink™ tool. We found that within the same field the yield fluc­tu­ated from -20% to +20% of the average yield. Then we built vari­able rate seeding maps using the Xarvio™ tool.”

To better fulfil the needs of its customers, Coulon has grad­u­ally acquired five Monosem preci­sion drills. “These are elec­tric-drive drills, designed for auto­mated seed rate vari­a­tion and switching off of row units,” confirms Anthony Hardou, partner in charge of the equip­ment fleet.

Site specific seed rate gives an optimum stand, and up to 10% in seed savings.

Jean-Louis Mary

Savings on seed is under­stand­ably attrac­tive for customers, when the cost of certain recent vari­eties is close to €110 (£91) per seed unit (50 000 kernels), at a rate of 1.5 to units/ha. “We managed to save 7-10% on seed usage, which covers the slight addi­tional costs in using our service, partic­u­larly on the least advan­ta­geous plots,” recog­nises Mr Mary. The yield history was accu­mu­lated free of charge, and is now avail­able to farmers for any other oper­a­tion, aimed at correctly eval­u­ating the soil capital of a plot.

The latest addi­tion to the preci­sion drill market, Monosem’s ValoTerra is 100% elec­tric. It allows all vari­able seeding rates with a preci­sion accu­racy as low as 100 seeds/ha.

Net gain through vari­able rate seeding: At least €20/ha (£16.60), in 80% of the trials

Over the past seven years, the seed company Dekalb has been working across Europe on vari­able rate seeding, and its adap­ta­tion to the soil’s poten­tial, reports Entraid’ Maga­zine (March 2020). Dekalb has tested vari­able rate seeding with farmers in the field. Eight out of 10 trials led to an effi­ciency gain with vari­able rate seeding, with the addi­tional margin amounting to several tens of euros per hectare. “This is the result of combining our knowl­edge about plant genetics and the farmer’s knowl­edge about the fields,” the Dekalb experts explain.

The Breton co-oper­a­tive D’Aucy has also tested vari­able rate seeding. First point: Switching off seeding rows when not needed reduces seed usage by 1-6%, depending on the shape and size of the field. Based on 3.5% savings, the addi­tional cost of the drill and the GPS pays for itself after sowing 180ha per year, according to D’Aucy. Second point: Vari­able rate seeding allows a gain of around €20/ha (£16.60) (service costs included), which makes the drill more prof­itable than a tradi­tional machine in all situ­a­tions. The co-oper­a­tive uses vari­able rate seeding maps, produced in the form of sepa­rate service, invoiced at €14/ha (£11.60).

Vari­able rate seed map inserted in the cab’s console. Foto: Fron­tierAG

The year 2021, with its record yields, should not make us forget that the trend is towards declining rain­fall, says Mr Mary. “We have always been surprised at obtaining so much maize with so little water avail­able in certain fields, and this is thanks to the site-specific adjust­ment of seed rates.”