Pengertian dan ruang lingkup pengawetan tanah Pengawetan tnh adalah penempatn setiap bidang tnh pd cr penggunaan yg sesuai dgn ke mampuan tnh tsb dan menggunakannya sesuai dgn syarat2 yg dperlukan agar tdk terjadi kerusakan tnh. Usaha pengawetan tnh ditujukan untuk; 1.Mencegah kerusakan tnh oleh erosi 2.Memperbaiki tnh yg rusak 3. Menetapkan kelas kemampuan tnh dan tindakan atau perlakuan yg diperlukan agar tnh dapat digunakan untuk waktu yg tidak terbatas

Pengawetan air; penggunaan air yg jatuh ke tnh untuk pertanian seefisien mungkin, dan pengaturan waktu aliran shg tidak terjadi banjir yg merusak sewaktu musim hujan dan terdapat air yg cukup selama kemarau. Oleh sebab itu ada 2 hal yg penting harus diperhatikan ; 1. memelihara jlh dan kualitas air, melalui pengelolaan dan penggunaan tnh yg baik 2. memaksimumkan manfaat air melalui penerapan cara-cara yg efisien.

What is erosion? Wind or water erosion is the physical wearing of the earth’s surface. Surface soil material is removed in the process. Why should we be concerned? Erosion removes topsoil, reduces levels of soil organic matter, and contributes to the breakdown of soil structure. This creates a less favorable environment for plant growth In soils that have restrictions to root growth, erosion decreases rooting depth, which decreases the amount of water, air, and nutrients available to plants.

Erosion removes surface soil, which often has the highest biological activity and greatest amount of soil organic matter. This causes a loss in nutrients and often creates a less favorable environment for plant growth. Nutrients removed by erosion are no longer available to support plant growth onsite, but can accumulate in water where such problems as algal blooms and lake eutrophication may occur. Deposition of eroded materials can obstruct roadways and fill drainage channels. Sediment can damage fish habitat and degrade water quality in streams, rivers, and lakes. Blowing dust can affect human health and create public safety hazards.

Mekanisme terjadinya erosi Soil erosion is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions. Mekanisme terjadinya erosi 1. penghancuran agregat dan pelepasan partikel tnh dr massa tnh 2. Pengangkutan 3. pengendapan

MEKANISME terjadinya erosi

Erosi Peristiwa pindah atau terangkutnya tnh atau bagian tanah dari satu tempat ke tempat lain oleh media alami. Menurut agen penyebabnya, dikenal ada 2 jenis erosi yaitu; erosi angin dan arosi air Menurut jenisnya ada 2; erosi geologi dan erosi dipercepat Menurut bentuknya; erosi lembar, erosi alur, erosi parit, erosi tebing sungai, longsor dan erosi internal

DID YOU KNOW? Annual soil loss in South Africa is estimated at 300 - 400 million tonnes, nearly three tonnes for each hectare of land. * Replacing the soil nutrients carried out to sea by our rivers each year, with fertilizer, would cost R1000 million. * For every tonne of maize, wheat, sugar or other agricultural crop produced, South Africa loses an average of 20 tonnes of soil. * The FAO (Food and Agriculture Organisation, a branch of United Nations) estimates that the global loss of productive land through erosion is 5-7 million ha/year.

* speed - the faster either moves, the more soil it can erode; CAUSES OF SOIL EROSION Wind and water are the main agents of soil erosion. The amount of soil they can carry away is influenced by two related factors: * speed - the faster either moves, the more soil it can erode; * plant cover - plants protect the soil and in their absence wind and water can do much more damage.

Water erosion: - small rills and channels on the soil surface, soil deposited at the base of slopes, sediment in streams, lakes, and reservoirs, pedestals of soil supporting pebbles and plant material. Water erosion is most obvious on steep, convex landscape positions. However, erosion is not always readily visible on cropland because farming operations may cover up its signs. Loss of only 1/32 of an inch can represent a 5 ton per acre soil loss.

What are some signs of erosion? Wind erosion: - dust clouds, - soil accumulation along fencelines or snowbanks, - a drifted appearance of the soil surface.

THE IMPORTANCE OF PLANTS Plants provide protective cover on the land and prevent soil erosion for the following reasons: * plants slow down water as it flows over the land (runoff) and this allows much of the rain to soak into the ground; * plant roots hold the soil in position and prevent it from being washed away; * plants break the impact of a raindrop before it hits the soil, thus reducing its ability to erode; * plants in wetlands and on the banks of rivers are of particular importance as they slow down the flow of the water and their roots bind the soil, thus preventing erosion. The loss of protective vegetation through deforestation (see Enviro Facts "Deforestation"), over-grazing, ploughing, and fire makes soil vulnerable to being swept away by wind and water. In addition, over-cultivation and compaction cause the soil to lose its structure and cohesion and it becomes more easily eroded. Erosion will remove the top-soil first. Once this nutrient-rich layer of soil is gone, few plants will grow in the soil again. Without soil and plants the land becomes desert-like and unable to support life - this process is called desertification (see Enviro Facts "Desertification"). It is very difficult and often impossible to restore desertified land.

POLITICS, ECONOMICS AND SOIL EROSION To understand soil erosion we must be aware of the political and economic factors affecting land users. In South Africa apartheid policies ensured that 42% of the people lived on 13 % of the land (the "homelands"). This overcrowding has resulted in severe erosion. As the land became increasingly degraded and thus less productive, subsistence farmers were forced to further overuse the land. The intensive agriculture and overgrazing that followed caused greater degradation. Soil erosion can be seen as both a symptom of underdevelopment (i.e. poverty, inequality and exploitation), and as a cause of underdevelopment. A reduced ability to produce, invest one's profit and increase productivity, contributes to increasing poverty, and can lead to desertification, drought, floods, and famine. On commercial farm lands, overstocking, mono-cropping, and the ploughing of marginal lands unsuitable for cultivation has led to soil erosion and desertification. Frequently these practices have been unwittingly encouraged by the state offering subsidies which made it profitable to exploit the land in the short-term.

Bentuk erosi Erosi lembar (sheet erosion) Erosi alur Erosi parit Erosi tebing sungai Longsor Erosi internal

Long-term soil erosion results in: - persistent and large gullies, - exposure of lighter colored subsoil at the surface - poorer plant growth.

Erosi lembar

Erosi alur/rill erosion

Erosi parit

Erosi tebing sungai

Erosi tebing jalan

Longsor/landslide

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