Winter barley fertiliser and establishing spring beans

As ground conditions improve, Teagasc Crops Specialist, Shay Phelan looks at the optimum time to apply fertiliser to winter barley crops and shares key advice on establishing spring beans and managing pigeon damage in winter oilseed rape crops.

Winter barley

Winter barley crops are now approaching the time for the first application of fertiliser. However, for most crops, there is little growth at the moment; soil and air temperatures in Oak Park this week are around 4^OC, so wait until there is a sign of growth before applying compound fertilisers - especially if they contain nitrogen. Trials carried out in Oak Park clearly show that early March is the ideal timing for applying the first application of nitrogen to crops and usually gives most yield compared to February or mid-March applications. However, the yield penalty for applying in February is usually small provided there isn’t heavy rain after application, which will increase nitrogen loss.

September drilled crops tend to have an extra tiller on them compared to October drilled crops and are well on course to have between 1,000 and 1,200 shoots/m². Growers should also be aware that early nitrogen can increase disease and lodging pressure, so for disease-prone and/or weak straw varieties you need to carefully weigh up the risks of applying early nitrogen.

Spring beans

The recent dry weather has encouraged some growers to start to drill spring bean crops, mid- February to mid-March is generally considered the best time to drill bean crops. Aim to drill 40-45 seeds/m² to establish 30-35 plants/m². Use the thousand seed weight of the different varieties to accurately calculate the correct seed rate; don’t rely on the drill setting used last year. The table below shows the typical seed rate at the different thousand seed weights.

Table 1: Seed rate to establish 32 plants/m²

Beans like sites that have high fertility and generally do not perform well in index 1 or 2 soils for both phosphorus (P) and potassium (K). They also perform better on moisture retentive soils rather than soils which are prone to drought. In soils that are at index 3, you will need 20kg/ha of P and 40kg/ha of K.

Weed control should be carried out pre-emergence. as the available herbicides will give greater control of broadleaf weeds. Options include Nirvana, Stallion, Emerger, Centium, Pendimethalin or Defy.

Winter oilseed rape

Most crops have been heavily grazed by pigeons over the last few weeks, with many now having a Green Area Index (GAI) of less than 1.0. This means that nitrogen has been removed from the crops by the pigeons, as nitrogen is stored in the leaves, so this nitrogen will have to be replaced by chemical nitrogen.

Figure 1: Green Area Index (GAI) of 0.5 in a winter oilseed rape crop

Crops with a GAI of less than 1.0 will need approximately 60-70kg/ha of nitrogen in late February. This is also a good time to apply sulphur as oilseed rape requires approximately 30-35kg/S/ha. ASN is generally a good option at this stage.

Winter crop walks

The Teagasc series of winter crop walks starts on Monday, February 17^th in Dublin and continues on for the rest of the week. See table 2 below for the dates and times of walks in your area.