与放牧有关的土壤健康

J. Volk W. 巴克和J. Richardson, NDSU Animal and Range Sciences and 土壤 Science Departments

土壤, 这是科多地区最重要的自然资源, determines the economic returns and the success of the rancher. 土壤健康和草地植被的管理应以促进土壤质量和牧场整体质量为目标. Rich, deep soils result in productive bio-diverse grasslands. Conversely, the grasslands produce the rich deep soils, an example of mutual synergism. 健康土壤需要根系周转来促进土壤微生物活动和提供土壤有机质, and vegetation needs healthy soils with their stable structure, and water penetration and retention properties that result in deep robust root growth. 具体的土地管理措施促进了土壤健康和草地生物多样性的协同作用.

俄罗斯人称草原土壤为“Chenozems”或“黑土”, 加拿大人称其为北欧黑土, 在美国.S. we call them Mollisols or soft soils to point out their mellow nature. 不管名字是什么，它们的肥沃和肥沃意味着它们是世界上最多产的土壤. 草原植被根系生物量大，周转快，为土壤贡献了大量的有机质. The conversion of organic matter results in the black color, 软稳土结构, 以及水渗透性能的提高.

方法

在这项研究中，我们使用了从8种土地利用方式中分别提取的6个土壤芯:轻度连续放牧, 历史上短暂放牧, 早期大量放牧, 集约化连续放牧, 适度连续放牧, 后期大量放牧, 闲置(CRP)和不使用本机范围, 两次轮牧. The soil cores were evaluated in terms of soil macro- porosity, 土壤的颜色, 根系分布与深度, and additional observations of root fragility and soil texture. 仅使用了两个代表几乎相同景观位置的范围站点:粉砂质和溢流.

结果与讨论

我们的土壤健康标准表明，两次轮牧促进了“最佳”土壤健康. The abundant root growth over 15”deep was observably greater than other systems. 连通的大孔隙允许高水分渗透和根系渗透至少达到那个深度，甚至可能更深. 深层的活性根系有利于植物更好地获取养分，因为它们有更大的土壤容量来收集养分. 草的根从光合作用中吸收了大量的碳，增加了土壤有机质. 牧草产量最高, 最高的生物多样性, and most native plants resulted from twice over rotational grazing. 土壤健康和生态系统健康得到改善.

我们认为轻度连续放牧的牧场次之. 土壤表面很少有根垫地现象，根系分布良好，根系结实. 土壤 structure was well aggregated with large pores deeper than 15”. 两次轮牧和轻度连续放牧的牧草具有较高的生物多样性. We concluded that 土壤健康 was positively influenced by biodiversity. Diverse plant communities do not produce root bound conditions nor root matting. 随着时间的推移，豆科植物的存在促进了有机质的增加以及氮的自然固定.

The third group included historic short-duration / miscellaneous pastures. 这里的情况很有趣，因为这些牧场似乎比其他牧场更干燥, even though all pastures have approximately the same topography. 保水能力低于上述土地利用方式. Root matting was observed but these soils did not appear to be root bound. 总体而言，这些牧场土壤结构良好，根系分布良好，透水性良好.

The fourth group included the heavily grazed late season pasture. Plant diversity was high on this pasture which positively influenced root distribution. 根垫存在，但没有到根部在表面被根束缚的地步. 大约是1.在这些地点观察到5英寸的根垫. 土壤结构仍然由大的聚集孔组成，允许深水渗透和深层强健的根系分布.

 The fifth group included the moderate continuously grazed pasture. 这种土地利用通常产生的根垫为1.5” to 2”. Root disposition was not very deep and roots were thin and fragile. 根垫以下可观测到的垂直孔隙度较差，阻碍了水分的渗透. 这些地点为浅层土壤，各自范围内的地点和土壤发育似乎很差. We concluded that the lack of good aggregation below the root mat and large massive, 软弱的土壤结构是土壤劣化的表现. A change in color of the soil from black to gray at approximately 10” occurred. This layer impedes water percolation and root growth past that point. 总的来说，我们认为这片土地最多算是公平的.

The sixth group included the intensive continuously grazed pasture. 这个牧场的根垫大约是2到3英寸。, but still promoted fair root growth within that zone but not deeper. The soil itself below the mat was very hard with poor observable vertical porosity. This poor porosity leads to low water percolation and fragile root development. 这种土壤的可取之处是植物的多样性. 一种很好的草的混合物, 福布斯, and legumes on this site makes the 土壤健康 better than one should expect.

第七组包括大量的早期放牧. 在适度放牧的牧场中可以观察到1.5英寸到2英寸浓密的根垫. The vertical soil structure was weak and nearly clod-like with very few vertical pores. 垂直孔隙的缺乏使根部无法深入渗透，我们认为水的渗透将受到阻碍. 由于土壤结构退化，根系非常脆弱，无法深入土壤. This site was dominated by Kentucky bluegrass, which is a sod former. 早季重度放牧与集约放牧系统的差异在于植物多样性对土壤健康的影响. A more diverse plant community occurred with the intensively grazed pasture.

我们观察到的最贫瘠的土壤是在未使用的原生范围和闲置(CRP)土地上. These sites had a 2”-3” very dense root mat and high surface litter content. The roots are kinked and fragile and only penetrate approximately 6”. 垂直结构差，阻碍土壤孔隙度，阻碍水分渗透或根系生长超过6英寸。. 有一个剧烈的颜色变化在大约6“从黑色到浅灰色. 灰色的土壤几乎像一个水屏障，阻止任何进一步的根系渗透和深水渗透. 我们假设水是横向流出的. The vegetation on these sites is virtually a monoculture of smooth brome. 我们认为CRP和闲置的原生地需要放牧干扰和增加植物多样性.

结论

In summary, 土壤健康 depends on root growth and grazing and plant species diversity. 良好孔隙度和土壤有机质的发育与根系生长深度大于12”和轮牧或轻/中度连续放牧所观察到的生物多样性直接相关. 两次轮作和闲置(CRP)土地的土壤差异可以用肉眼看到. 特别是, 轮牧系统土壤具有丰富的垂直孔隙和根系分布.

未使用的原生牧场和闲置土地(CRP)的土壤质量较低，原因是土壤表面有密集的凋落物垫，没有被纳入土壤剖面. 因此, 放牧和物种多样性是对闲置土地和CRP土地土壤和植被健康产生积极影响的建议. 适度放牧可减少凋落物的堆积, 增加水分和根系的渗透，从而将土壤有机质融入土壤中，而不是像闲置土地和CRP土地那样在土壤表面.