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Topics : Soil Fertility for Forage Crops : Maintenance


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Plant Analysis for Managing Fertility of Established Forage Stands

Plant tissue analysis can be a very useful tool for managing the nutritional status of an established perennial forage crop. Plant analysis is usually a post-mortem program for annual crops. It can provide information on what was wrong with a crop but often it is too late to do anything about it. With perennial crops, such as most forages, plant analysis can provide very timely information that can be used to adjust the fertility management of the established crop. Plant analysis has several roles in improved forage management. Since a soil test only determines the nutrient status in the surface soil, a plant analysis can complement the soil test because it monitors the nutrient status throughout the rooting zone. Plant analysis can detect problems where the soil may be optimum but where some other factor, such as compaction limited root growth, inhibits the plant's ability to take up the available nutrients. Finally, plant analysis is currently better than a soil test for determining the micronutrient status of a crop.

Plant analysis results for forage crops are commonly used in two ways. They are most often used to diagnose production problems. In this case, samples are collected from the problem area and from a nearby area where the problem is not evident. Comparison of the results from these two samples will usually lead to a straight forward diagnosis of a nutritionally related problem. When plant analysis is used in this way it is very important that the samples be taken consistently. The same plant part must be sampled at the same stage of growth for the comparison to be valid. The second common use of plant analysis is to routinely monitor the nutritional status of the crop. In this type of program the nutrient levels in the plant are compared to established norms for optimum production of the crop. The sufficiency levels for plant analysis for some of the forage crops are given in Table 5. As noted above, when comparing plant analysis values to these sufficiency levels, the correct plant part must be sampled at the proper stage of growth.