ID-158

Managing Steep Terrain for Livestock Forage Production D.C. Ditsch, G. Schwab, J.D. Green, Department of Plant and Soil Sciences; J.T. Johns, R. Coleman, T. Hutchens, Department of Animal and Food Sciences; L. Piercy, Department of Biosystems and Agricultural Engineering

Introduction

Kentucky has a diversified landscape that ranges from level river bottoms to steep mountainous side slopes with narrow ridge tops. Soils that form or develop on each of these landscape positions offer various land use opportunities and limitations for agricultural production. Many of the grass and legume species adapted to Kentucky’s climate and soils can be used for livestock production on steep terrain. However, the unique characteristics of steep terrain often result in soil productivity limitations that should be considered when managing these same grass and legume species for pasture and/or hay production. Decades of surface mining in the eastern region of the state have created extensive acreages of steep reclaimed land. These lands currently support an abundance of underutilized forage that could be managed for horses, beef cattle, and goat production. This publication addresses the agronomic, economic, and human safety aspects of managing steep terrain for livestock forage production.

What Is Steep Terrain?

The slope of a field refers to the number of feet of rise or fall in 100 feet of level distance (Figure 1). This is a very important landscape characteristic because it affects the productivity of the soil in many ways. In general, as the percent slope of a field increases, productivity decreases because the soil’s erosion hazard increases and the ability of the soil to supply moisture to plants decreases. Steep terrain soils are often low in natural fertility due to the loss of topsoil from past erosion. Figure 1. Percentage of slope. Soil scientists use slope and other soil characteristics to group soils into capability classes to indicate limitations in use and risks of damage by agricultural practices (Table 1). In general, soils in capability classes I to IV (0 to 20% slope) are favorable for row crop production when 100’ run appropriate conservation crop-

Table 1. Land capability classes for land use decisions in Kentucky.1 Slope % of Total Range Class Land Area Description 0-2% I 0.7 Few limitations that restrict land use 2-6% II 20.1 Require moderate conservation practices 6-12% III 13.8 Require special conservation practices 12-20% IV 10.2 Require careful management and special conservation practices V 0.3 Not likely to erode but have other limitations impractical to remove (i.e., flooding, stoniness) 20-30% VI 14.4 Severe limitation, unsuitable for cultivation, limited to pasture and hay production 30-50% VII 26.4 Very severe limitation that restrict use to forest Other 14.1 Water bodies, pits, quarries, and rock outcrops 1 Source: 1977 Natural Resource Inventory, NRCS.

ping practices are used. The “steep terrain” designation for livestock forage production in this publication refers to soils in capability class VI (20 to 30% slope). These soils have severe limitations that are generally unsuitable for conservation row crop production and should be limited to pasture and hay production. Class VII soils have very severe limitations that restrict their use primarily to forest. Table 1 indicates the distribution of land in each of the land capability classes for Kentucky. 50’ rise (50% slope) 30’ rise (30% slope) 20’ rise (20% slope) 12’ rise (12% slope) 6’ rise (6% slope) 2’ rise (2% slope) 0’ rise (0% slope)

Very steep Steep Moderately steep Strongly sloping Gently sloping Nearly level

Soil Acidity and Liming

The most obvious is to use commercial fertilizers, but N fertilizers only increase productivity for the year in which they are applied, and they are more expensive in the long run. Annual applications of nitrogen fertilizers on steep ground are also a safety hazard because of the volume (100 to 150 pounds) required per acre, and multiple applications per year are required to obtain maximum productivity. A better alternative to annual N applications is to renovate using legumes like red or white clover. Once established, bacteria living on the clover roots will fix enough atmospheric N to meet the N requirements of the pasture. As long as there is at least 25% clover in the pasture, there is no need to apply N fertilizer. In fact, research results show that grass-legume mixtures without N fertilization produce higher yields than pure grass stands with maximum N fertilization. Forage quality is also higher for grass-legume mixtures. A third way to increase plant available N is to apply manure or tobacco stalks (Table 2). While these options might not be feasible for steep terrain, manure and plant residues are a good source of N and other essential plant nutrients and can be utilized in forage production. Phosphorus (P) and potassium (K) are the other two plant nutrients that are likely to be low in pasture systems. Soil test results show that about 37% of eastern Kentucky soil samples were low or very low in P, and about 50% were low in K. In these situations, applications of P and K fertilizer will increase yield only if soil pH is optimum and the forage has a good supply of N. Yield increases as a result of P and K applications are not as substantial as for N applications. Manure and tobacco stalks are a good source of P and K (Table 2). Research data over a number of years indicate that dry matter can be increased from about a ton per acre per year with no soil pH or nutrient management up to four or more tons per year with improved management. Proper fertilization can help increase total dry matter yield and protein content and can minimize seasonal shifts in production. However, unless the increased yields are utilized by grazing or hay harvest, there will be no return on the investment.

As with any other cropping system, lime and fertilizer management on steep terrain should begin with a composite soil sample from the area. Soil cores should be collected to a depth of 4 inches following the procedures outlined in University of Kentucky Extension publication AGR-16, Taking Soil Test Samples. Soil test results and fertilizer recommendations will let you know how much and which fertilizers to apply. The most common soil fertility problem on steep terrain is low soil pH. Low pH indicates that the soil is acidic, and plant growth will probably be reduced. A secondary effect of low pH is that less desirable species of plants begin to dominate the landscape. For example, soils with pH in the optimal range (6.0 to 7.0) will generally have a good mixture of grasses and legumes. As the pH drops below the optimal range, the legumes will disappear, and grasses will dominate. If the pH is allowed to drop into very low range (40%), while others prefer to graze gentle slopes (