Reducing the nitrate content of protected lettuce.

End of Project ReportA research project was carried out jointly between Teagasc, Kinsealy Research Centre and University College Dublin, Department of Crop Science, Horticulture and Forestry which studied the effects of cultivar, nitrogen fertilisation and light intensity on the nitrate content of protected butterhead lettuce. In a series of cultivar trials of winter and summer butterhead lettuce, significant differences in the nitrate content of the lettuce between cultivars were found only in one experiment. In this instance, the differences were not consistent between successive harvests. It was concluded that screening lettuce cultivars for tissue nitrate level is unlikely to contribute to an overall reduction of nitrate levels. The application of N in a liquid feed throughout the cropping period resulted in higher nitrate levels in lettuce plants grown in soil filled containers compared with a similar amount of N applied to the soil before planting. Withdrawing N for the final 10 days of the cropping period did not affect the nitrate content of the lettuce. In an experiment studying nitrogen source and rate on lettuce grown in containers, the use of calcium cyanamide as a N source resulted in lower nitrate levels in the lettuce and gave a reduced head weight compared with calcium ammonium nitrate (CAN) or ammonium sulphate. Increasing the rate of CAN or ammonium sulphate gave higher lettuce nitrate levels. A nitrification inhibitor reduced the soil nitrate levels especially with sulphate of ammonia as the N source but did not affect the plant nitrate levels significantly. The addition of chloride to the soil reduced nitrate levels in the lettuce. In a further fertilisation study using containers, calcium cyanamide again resulted in lower plant nitrate levels than CAN. Increasing the rate of CAN increased soil nitrate levels, lettuce head weight and plant nitrate levels. The relationship between soil nitrate levels, lettuce head weight and plant nitrate level indicates that the level of 100-150 mg·L-1 of nitrate N in the soil, advocated in the Code of Good Practice, is a compromise between maximising plant growth and minimising lettuce nitrate content. A comparison between CAN and calcium cyanamide in a border soil experiment again showed that the latter N source resulted in lower lettuce nitrate levels. In this experiment the addition of chloride to the soil did not affect plant nitrate levels. Lettuce was grown, in late summer, in small tunnels using a range of polyethylene cladding materials. Head weight correlated well with the overall light transmission of the materials. In one of the materials that had a low light transmission, lettuce nitrate content was doubled compared with those grown under the materials with high light transmission. Under both winter and summer conditions, the nitrate content of lettuce heads was not influenced by the time of day at which harvest took place. In experiments in which multiple harvests were carried out there was no consistent trend in nitrate content as the heads developed and matured. Within individual heads of lettuce there was a steep concentration gradient with the older outer leaves having much higher concentrations of nitrate than the younger inner leaves. Herbicides commonly used in protected lettuce production did not influence the nitrate content of the lettuce

Managing Spent Mushroom Compost

End of Project ReportThis project addressed how to manage spent mushroom compost (SMC), an issue of critical importance to the continued development of the Irish mushroom industry. The most important aim of the project was to devise a feasible strategy for the management of this material on an industry wide basis. There were two main components of the project, which were conducted in parallel. One analysed the structure of the mushroom industry and the logistics of handling, transporting and processing SMC. The other studied the agronomic properties of SMC in an effort to develop improved guidelines on the best use of SMC in crop production. Our analysis of the SMC management problem led us to conclude that a centralised approach should be taken when developing the solution strategy. The model solution that was formulated is based on the establishment of centrally located depots for SMC collection, temporary storage and possible processing. This approach facilitates a variety of environmentally acceptable SMC end uses ranging from land application to incineration. We examined a variety of possible end uses for SMC, including its use as an alternative fuel. In the immediate future, we believe the predominant end use for SMC will be as an organic manure for field crop production and as a soil conditioner in the landscaping industry. Uses of this type are in line with both Irish and EU legislation regarding waste management. Our analysis suggests that tillage and horticulture offer the best promise for realising the beneficial properties of SMC. We have tested SMC on field crops such as winter and spring wheat and potatoes and on glasshouse crops such as tomatoes. These experiments have shown that SMC increases soil organic matter and improves soil structure. SMC is a very effective source of K and P and also provides trace elements. It makes a contribution to N nutrition but most of the N does not become available to the crop in the first year. For best results therefore, supplementary N must be applied. Overall, our results indicate that SMC can be used with beneficial effects in field crop production. The mushroom industry should move forward with establishing centralised SMC handling facilities to enable the efficient collection, temporary storage, further processing and transportation of SMC to end users. An education and awareness campaign should be conducted amongst farmers, in areas removed from mushroom production, to introduce them to the benefits of SMC and ways to effectively utilise this material.Department of Agriculture, Food and the MarineEuropean Union Structural Funds (EAGGF

Reducing the nitrate content of protected lettuce.

End of Project ReportA research project was carried out jointly between Teagasc, Kinsealy Research Centre and University College Dublin, Department of Crop Science, Horticulture and Forestry which studied the effects of cultivar, nitrogen fertilisation and light intensity on the nitrate content of protected butterhead lettuce. In a series of cultivar trials of winter and summer butterhead lettuce, significant differences in the nitrate content of the lettuce between cultivars were found only in one experiment. In this instance, the differences were not consistent between successive harvests. It was concluded that screening lettuce cultivars for tissue nitrate level is unlikely to contribute to an overall reduction of nitrate levels. The application of N in a liquid feed throughout the cropping period resulted in higher nitrate levels in lettuce plants grown in soil filled containers compared with a similar amount of N applied to the soil before planting. Withdrawing N for the final 10 days of the cropping period did not affect the nitrate content of the lettuce. In an experiment studying nitrogen source and rate on lettuce grown in containers, the use of calcium cyanamide as a N source resulted in lower nitrate levels in the lettuce and gave a reduced head weight compared with calcium ammonium nitrate (CAN) or ammonium sulphate. Increasing the rate of CAN or ammonium sulphate gave higher lettuce nitrate levels. A nitrification inhibitor reduced the soil nitrate levels especially with sulphate of ammonia as the N source but did not affect the plant nitrate levels significantly. The addition of chloride to the soil reduced nitrate levels in the lettuce. In a further fertilisation study using containers, calcium cyanamide again resulted in lower plant nitrate levels than CAN. Increasing the rate of CAN increased soil nitrate levels, lettuce head weight and plant nitrate levels. The relationship between soil nitrate levels, lettuce head weight and plant nitrate level indicates that the level of 100-150 mg·L-1 of nitrate N in the soil, advocated in the Code of Good Practice, is a compromise between maximising plant growth and minimising lettuce nitrate content. A comparison between CAN and calcium cyanamide in a border soil experiment again showed that the latter N source resulted in lower lettuce nitrate levels. In this experiment the addition of chloride to the soil did not affect plant nitrate levels. Lettuce was grown, in late summer, in small tunnels using a range of polyethylene cladding materials. Head weight correlated well with the overall light transmission of the materials. In one of the materials that had a low light transmission, lettuce nitrate content was doubled compared with those grown under the materials with high light transmission. Under both winter and summer conditions, the nitrate content of lettuce heads was not influenced by the time of day at which harvest took place. In experiments in which multiple harvests were carried out there was no consistent trend in nitrate content as the heads developed and matured. Within individual heads of lettuce there was a steep concentration gradient with the older outer leaves having much higher concentrations of nitrate than the younger inner leaves. Herbicides commonly used in protected lettuce production did not influence the nitrate content of the lettuce

Managing Spent Mushroom Compost

End of Project ReportThis project addressed how to manage spent mushroom compost (SMC), an issue of critical importance to the continued development of the Irish mushroom industry. The most important aim of the project was to devise a feasible strategy for the management of this material on an industry wide basis. There were two main components of the project, which were conducted in parallel. One analysed the structure of the mushroom industry and the logistics of handling, transporting and processing SMC. The other studied the agronomic properties of SMC in an effort to develop improved guidelines on the best use of SMC in crop production. Our analysis of the SMC management problem led us to conclude that a centralised approach should be taken when developing the solution strategy. The model solution that was formulated is based on the establishment of centrally located depots for SMC collection, temporary storage and possible processing. This approach facilitates a variety of environmentally acceptable SMC end uses ranging from land application to incineration. We examined a variety of possible end uses for SMC, including its use as an alternative fuel. In the immediate future, we believe the predominant end use for SMC will be as an organic manure for field crop production and as a soil conditioner in the landscaping industry. Uses of this type are in line with both Irish and EU legislation regarding waste management. Our analysis suggests that tillage and horticulture offer the best promise for realising the beneficial properties of SMC. We have tested SMC on field crops such as winter and spring wheat and potatoes and on glasshouse crops such as tomatoes. These experiments have shown that SMC increases soil organic matter and improves soil structure. SMC is a very effective source of K and P and also provides trace elements. It makes a contribution to N nutrition but most of the N does not become available to the crop in the first year. For best results therefore, supplementary N must be applied. Overall, our results indicate that SMC can be used with beneficial effects in field crop production. The mushroom industry should move forward with establishing centralised SMC handling facilities to enable the efficient collection, temporary storage, further processing and transportation of SMC to end users. An education and awareness campaign should be conducted amongst farmers, in areas removed from mushroom production, to introduce them to the benefits of SMC and ways to effectively utilise this material.Department of Agriculture, Food and the MarineEuropean Union Structural Funds (EAGGF