Research needs on nitrogen and phosphate management in cereals and oilseeds

The HGCA has funded an agronomic R&D programme for some twenty years. Emphasis has been on research that could lead to improved farming practices in the short or medium term together with knowledge transfer to growers. A review of the programme on nitrogen and phosphorus and how it has related to Defra, SEERAD, BBSRC and commercial R&D has been conducted, and further R&D requirements identified, to add definition to the HGCA R&D Strategy 2007-10 introduced in January 2007.

There has been a significant HGCA-funded programme on nitrogen, concentrating on aspects that influence yield, grain quality and costs of production. This has complemented Defra and SEERAD research that has been devoted largely to environmental issues. Major HGCA-funded developments include canopy management in wheat and oilseed rape, evaluation of late application of nitrogen in breadmaking wheat, assessment of nitrogen requirement of barley for lager production and early prediction of grain quality in wheat. Defra and SEERAD research has covered losses of nitrogen from soil to water through nitrate leaching and from soil to air through denitrification (nitrous oxide) and volatilisation (ammonia).

There has been much less HGCA-funded research on phosphorus, reflecting the smaller perceived importance of this nutrient in crop production. The emphasis has been on methods for measuring or predicting the phosphorus status of individual crops. Defra on the other hand has funded a large programme on the main environmental issue associated with phosphorus, loss from soil to surface waters. Routes for loss have been identified and, for some situations, quantified.

Findings from HGCA-funded research have been communicated to growers and their advisers through workshops, conferences, roadshows, Topic Sheets and other publications.

Priority needs for further research or knowledge transfer were identified through meetings and discussions with those involved in cereals/oilseed rape R&D. Meetings were held with Rothamsted Research, ADAS, TAG, Reading University, Velcourt and AIC. In addition, views were sought from SAC and CCFRA. Many research or knowledge transfer requirements were proposed and, from these, seven were selected as generally considered important, relevant to growers and potentially suitable for HGCA funding. These seven requirements are listed below, not in general priority order though the first item has the widest importance:

1. Three aspects of soil nitrogen supply need attention:

i. The different methods for quantifying soil nitrogen supply, by estimation, measurement or both, need to be validated and compared. The relative contributions of soil mineral nitrogen, nitrogen mineralised during spring and nitrogen taken up by the crop over winter need to be clarified. Guidance then is needed on the choice of method for different circumstances taking account of cost and the degree of accuracy to be expected.

• There will be a need for field research, supported by desk study. Guidance for growers will then be needed.

ii. A method is needed for monitoring or modelling seasonal effects on soil nitrogen supply and for providing timely guidance on their impact on fertilizer recommendations.

• This is likely to involve collection of climatic and soil data for the period September to March each year with subsequent interpretation and dissemination to growers/advisers via web site or email.

iii. The extent to which soil nitrogen is utilised by crops affects nitrogen use efficiency and is a key component of many recommendation systems. Factors that affect the utilisation of soil nitrogen should be identified with a view to improving nitrogen use efficiency. The assumption that soil mineral nitrogen is recovered by the crop with 100% efficiency (with around 60% as the corresponding figure for applied inorganic nitrogen) needs validation for different agronomic conditions for both cereals and oilseed rape.

• Progress could be made using existing data and models such as SUNDIAL. However, additional field research also is likely to be required.

2. The need for current protein specifications for breadmaking wheat (usually minimum 13%) should be reviewed. Developments in varieties, in breadmaking techniques or in market requirements might allow the use of lower protein grain and smaller nitrogen applications.

• Initial action needed will be discussions with the baking industry on the potential opportunities for process changes.

3. Improving the nitrogen economy of oilseed rape will become more pressing if, as expected, a significant market for biodiesel develops. Methods for improving nitrogen use efficiency by oilseed rape, such as delayed or additional late nitrogen applications need evaluating. Possible interactions between nitrogen timing, green area index (GAI) development and variety in their effects on yield and optimum nitrogen rate need to be identified.

• Further field research supported by desk study would be needed. Subsequently, grower guidance would be necessary.

4. The biological basis for grain protein concentration as a retrospective indicator of nitrogen supply needs to be established. Any other practical indicators need to be identified for both cereals and oilseed rape. Once methods are established, guidance for growers in their use is needed.

• Progress could be made using existing data. It is unlikely that new field research would be necessary.

5. Guidance is needed on the relative benefits of standard values and chemical analysis in estimating the nitrogen and phosphorus concentrations in livestock manures. Where analysis is preferred, guidance also is needed on sampling methods and on the interpretation of analytical reports. Actions in this area need to be co-ordinated with developments in MANNER software.

• The need here is for clear guidance based on existing data. There should be no need for new field research.

6. The genetic potential of crops for improved nitrogen uptake and utilisation should be better exploited. More routinely gathered information is needed on nitrogen use efficiency in different crop varieties. Variety testing for Recommended Lists should include field trials at more than one rate of applied nitrogen to provide relevant data.

• An amendment to the current protocol for RL testing would be needed to include a number of field trials at more than one rate of applied nitrogen. Initially, this might be applied to winter wheat and winter oilseed rape.

7. The basis for phosphorus recommendations in England and Wales is the soil P index. In the current edition of RB209, index 2 is set as the target for arable crops but it is not clear that this index is most appropriate for all soil and crop conditions. Critical soil phosphorus concentrations to meet economic and environmental objectives need to be identified for a range of soils. Conditions that affect the critical concentration need to be identified.

• New field research would be required but this would be routine in nature with a low risk of not obtaining necessary data.

8. Growers need greater awareness of the environmental issues associated with phosphorus and of the ways in which phosphorus can move from soils to water. Clear guidance is needed on identification of high-risk fields and farming practices and on practical mitigation methods.

• No field research would be needed. The requirement is for clear guidance based on existing data.