With the relatively mild winter and early spring, crop growth has continued quite well over the last few months, with very few frosts to hold crops back. Some crops especially early sown barley and oats are beginning to look a little bit leggy and many growers are concerned about missing crucial applications around growth stage 30. However to accurately identify the internal growth stage you will need to peel back the different leaves to reveal the location of the head and node. Only then should key decisions be made.
Winter crops are showing signs of spring growth in the last week where soil temperatures are on average 7 - 8o C in most of the tillage areas. Early growth can be seen in winter oilseed rape where the flower buds are starting to rise above the canopy in advanced crops. Winter barley is starting to show to show signs of nitrogen deficiency particularly on light free draining soils and first nitrogen application will be applied when weather conditions are favourable.
Early sown winter barley is approaching GS 30 but growth is still slow and as a result these crops may stay at GS 30 for a longer than normal period of time. To reduce losses from fertiliser the first split of N should be small (50kg/ha) as crop demand is low but the N,P,K compound may dictate amount applied. Ensure weather conditions at the time of application are good to reduce the risk of losses and Teagasc research has shown that there is no detrimental effect on yield if application is delayed.
Low levels of BYDV have been reported in winter barley in the south of the country. Currently it is confined to a few early sown crops and the levels are low but it will take an extended period of growth before the true extent of BYDV will be known. Some level of BYDV is not surprising as the autumn/winter has been exceptionally mild and aphids were caught in the suction tower in Cork during December, January and February. Aphid flight did not begin in Cork till May in 2021. Insecticide use will not reduce BYDV at this stage.
Disease levels in winter barley are low but net blotch and low levels of mildew are evident in places. It is too soon for disease control but crops need to be monitored as tiller death from disease will reduce yield.
The risk of lodging may be higher this year due to good autumn growth but it is too soon for growth regulation. Successful growth regulation needs actively growing crops so wait till first N is applied and apply PGR to actively growing crops.
Winter oats is also approaching GS 30 and mildew is present in crops in sheltered areas. An assessment of lodging risk is important and Teagasc research shows that a split PGR programme at GS 30 and GS 32 will give the best results. Similar to winter barley wait for active growth before applying PGR.
There are no reports of yellow rust in winter wheat and first nitrogen can be delayed till mid March for most crops, thin or slug damaged crops or crops at risk of take-all will need an earlier N application.
Winter oilseed rape has grown well over the winter and many crops have GAI > 2. Nitrogen can be delayed on these crops for a few weeks and the total N applied should be reduced. The first crops that require N this season are pigeon grazed crops. Where the GAI is <1.0, apply 60kg/ha N as soon as conditions allow and follow up with a second application in mid March. Refer to canopy management and fertiliser section for details on calculation of GAI and fertiliser recommendations. Oilseed rape nitrogen calculator is available here
Light leaf spot is evident in many crops and should be treated once found with Proline 0.5L/ha.
Given the cost of fertiliser it is very tempting to reduce or omit P and K’s in 2022 to control production costs. Tailoring P and K rates in 2022 should be based on farm soil fertility levels. The soil P & K index (1 to 4) shows the soils ability to supply P and K during the growing season see table 1 below. Soils with higher indexes will have a higher grain yielding ability due to higher P and K supplies.
Soils at Index 1 & 2 will be most responsive to applied P & K and have a very low to low P and K supply. For spring cereals where possible combine drill P at sowing time to increase the efficiency of applied P fertiliser. It will be important to fertiliser the crops on these soils to their expected grain yield in potential. Teagasc are recommending fertilising to crop yield potential in 2022 i.e. replacing off takes (& omitting additional P & K application for build-up in 2022).
Soils at Index 3 have a good nutrient supply, aim to replace P, and K removed at harvest time to maintain soil fertility in the optimum range (Index 3). Omitting P and K will result in soil P and K levels declining thus reducing grain yield potential in the years ahead. We are recommending fertilising to crop yield potential in 2022 i.e. replacing off takes (& omitting additional P & K application for build-up in 2022)
Soils at Index 4 are very fertile and have a good supply of P and K to meet crop requirements during the growing season. Up to date soil analysis will help identify these soils on the farm. The Teagasc soils database shows that 31% of tillage soils are at Index 4 for P & K in 2020 offering a major saving on P & K applications in 2022.
Table 1 – Soil Nutrient Index, Response & Soil Test Range for P & K
Unlikely / tenuous
0 – 3.0
3.1 – 6.0
6.1 – 10
0 – 50
51 – 100
101 – 150
The level of growth from September right thorough to December was exceptional this year. The growth from cover crops was high with most crops trapping a significant amount of nitrogen. Teagasc sampled a number of crops around the country for bimoass ( dry matter ) and nitrogen content. Green covers produced between 10 to 51 t/ha of fresh material and recovered 12 to 70 kg N/ha for green covers. However the availability of nitrogen from these crops is much less than
Some excellent background information on cover crops is available from the proceedings of the National Tillage Conference 2020 (Page 43). Research in Oak Park has shown that, in general, the effects of cover crops, compared to bare fallow or natural regeneration, on yield of succeeding cereal crops under Irish conditions are variable, often small and sometimes negative. Significant yield benefits in succeeding crops through the use of cover crops occurred infrequently. This concurs with findings in other European countries.
The table below outlines the main findings from Teagasc results in cover crops and the combined results of samples taken this year.