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Crop Establishment Start early to build base for


higher winter wheat yields • Assess crops soon aſter harvest • Calculate appropriate seed rate • More plants better than too few


G


rowers are being advised to maximise the yield po- tential of next year’s win- ter wheat by adjusting seed rates in light of the challenging 2019/20 season.


As harvest draws to a close, it is a good time to reflect on what went well and what could have been improved, says Hutchin- sons technical support manager Neil Watson. Weather aside, one standout factor for many grow- ers this season was seed rates, he adds. “We often underestimate the number of plants required and overestimate establishment per- centages,” says Mr Watson. Get- ting these factors right is central to setting strong foundations for


tial of individual fields – consid- ering soil type, location, climate and historic performance – be- fore working back to identify the plant population and seed rates required to achieve this. “We know there is a direct cor- relation between grain number per unit area and yield, so use this as a starting point.” Yield is a combination of three components, says Mr Wat- son. These are ears per square metre, grains per ear and thou- sand grain weight. In most sea- sons,wheat crop can compensate for a deficit of one component by increasing the others – but there are limits.


Growers should estimate the realistic yield potential of individual fields, says Neil Watson


optimum yields, he advises. The starting point is to esti- mate the realistic yield poten-


The correlation between yield potential and seed rates. Wheat crops can make up for a deficit in one factor by compensatory realignment of others – but there are limits.


Target yield (t/ha)* Grains/m2


Grains/ear Ears/m2


Tiller survival Tiller produced Tillers per plant


Established plant population Establishment


Sowing rate (seeds/m2 ) 9


18,000 48


375


45% 833 3.5


238 85% 280


* Notes • Assumes average seed weight of 50mg TGW • Three key components of yield: eg 375 ears/m2


11


22,000 48


458 45% 1017 3.5


290 85% 341


13


26,000 48


541


45% 1202 3.5


343


85% 405


Some people talk about till- ering capacity, but fail to appre- ciate that wheat produces only two ears or so per plant by har- vest. This makes it important to ensure enough plants are in the ground at the start of the season, otherwise yield potential could be limited from the outset.


Different factors “Generally, it is better to have too many plants than too few, pro- viding land can support crop de- mands through the season,” says Mr Watson.


*48 grains/ear = 18000 grains/m2 * TGW 50mg = 9t/ha • Establishment: takes into account germination % and establishment losses


Calculating the appropriate seed rate depends on many in- terlinked factors. They include soil type, fertility, seedbed condi- tions, sowing date and establish- ment percentage. Early sowing is the best way to increase yield po- tential, so long as grassweeds, dis- ease and lodging can be managed. “Sowing date is the only way to influence tiller production, as all other factors affect tiller sur- vival,” says Mr Watson. Tiller sur- vival is typically only around 45%.


How to determine seed rate


Whatever the drilling date, an accurate estimate of likely es- tablishment is essential to cal- culate the seed rate needed to achieve a target plant popula- tion. For most, the challenging 2019/20 season is likely to be a low water mark for what is achievable. A normal autumn provides a more typical indi- cation. This can be done any- time, even immediately after harvest.


Growers should select rep- resentative areas of the field – taking into account high or low-yielding areas highlighted on yield maps – and count the number of root balls. This indi- cates the number of plants per square metre.


C M Y CM MY


This figure should be com- pared against the seed rates sown last autumn to estimate establishment percentage. Counting the number of till- ers per plant will indicate, along with plant numbers, the final ear density of the crop. “Growers may be shocked at the results, especially after such a difficult season, says Neil Watson of Hutchinsons. “Some sites drilled late into wet conditions have seen establish- ment down to 40%.”


CY CMY K


There will hopefully be no repeat of those conditions this autumn and establishment will be closer to a more typical 60- 85%. But Mr Watson says grow- ers must be realistic because establishment rates can vary considerably, even within fields. Precision farming systems and variable seed rates may be useful for managing variability.


Low seed rates can limit year potential from the outset.


18 ANGLIA FARMER • SEPTEMBER 2020


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