Soil Composition Zopangira Dothi (Soil Composition)
Soil is one of the most important natural resources for farming in Malawi. Whether you are growing maize in the Central Region plateau around Lilongwe, cultivating tobacco in Kasungu, or tending vegetable gardens along the shores of Lake Malawi, the success of your crops depends on the quality of the soil beneath them. But what exactly is soil made of? Soil is not a single substance , it is a mixture of four main components: mineral matter, organic matter (humus), water, and air. Understanding these components and how they interact is essential for every farmer and agriculture student.
\n\nMineral Matter (approximately 45% of soil)
\n\nMineral matter makes up the largest portion of soil by volume. It consists of tiny particles that come from the weathering (breaking down) of rocks over thousands of years. Rocks are broken apart by physical forces such as temperature changes, wind, and water, as well as by chemical reactions. The resulting particles vary greatly in size, and this size determines the soil’s texture. There are three main types of mineral particles:
\n\nSand particles: The largest mineral particles (0.05–2.0 mm in diameter). Sand feels gritty when rubbed between your fingers. Sandy soils, common in parts of the Shire Valley and along lakeshores, have large spaces (pores) between particles, which means water drains through quickly and air moves in easily. However, sandy soils hold fewer nutrients because water washes them away.
\n\nSilt particles: Medium-sized particles (0.002–0.05 mm). Silt feels smooth and silky, like flour. Silt particles hold water and nutrients better than sand but not as well as clay.
\n\nClay particles: The smallest mineral particles (less than 0.002 mm). Clay feels sticky when wet and forms hard clumps when dry. Clay soils hold large amounts of water and nutrients because the tiny particles pack closely together, leaving very small pore spaces. However, clay soils can become waterlogged and difficult for roots to penetrate. Many soils in the dambo (wetland) areas of Malawi are rich in clay.
\n\nMost agricultural soils in Malawi are a mixture of sand, silt, and clay, called loam. Loam soils are generally considered the best for farming because they balance water retention, drainage, aeration, and nutrient-holding capacity.
\n\nOrganic Matter / Humus (approximately 5% of soil)
\n\nOrganic matter consists of decomposed and decomposing remains of plants and animals. When leaves, roots, crop residues, manure, and dead organisms break down through the action of bacteria, fungi, earthworms, and other soil organisms, they form a dark, spongy material called humus. Although organic matter makes up only about 5% of soil volume, its importance to agriculture is enormous:
\n\nHumus improves soil structure by binding mineral particles together into aggregates (crumbs), which creates spaces for air and water movement.
\n\nIt increases the soil’s ability to hold water, which is especially important during Malawi’s dry season when crops can suffer from moisture stress.
\n\nHumus supplies essential plant nutrients such as nitrogen, phosphorus, and sulphur as it continues to decompose.
\n\nIt provides food and habitat for beneficial soil organisms like earthworms, which further improve soil structure through their burrowing activity.
\n\nFarmers in Malawi can increase organic matter in their soils by incorporating crop residues (such as maize stalks and groundnut shells), applying compost or farmyard manure, and practising green manuring with cover crops like Tephrosia vogelii or sun hemp (Crotalaria juncea).
\n\nSoil Water (approximately 25% of soil)
\n\nWater occupies the pore spaces between soil particles. It is not pure water but a soil solution , water with dissolved mineral nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium. Plant roots absorb these dissolved nutrients from the soil solution through a process called osmosis. Without soil water, plants cannot access the nutrients they need, even if the soil is rich in minerals.
\n\nThe amount of water a soil can hold depends on its texture. Clay soils hold the most water because their tiny particles create many small pore spaces. Sandy soils hold the least water because their large pore spaces allow water to drain through quickly. During Malawi’s rainy season (November to April), soils may become saturated with water, especially in low-lying areas and dambos. When soil is waterlogged, water fills nearly all the pore spaces, pushing out the air and suffocating plant roots. This is why good drainage is essential for most crops.
\n\nSoil Air (approximately 25% of soil)
\n\nAir fills the pore spaces in soil that are not occupied by water. Soil air has a similar composition to atmospheric air but contains more carbon dioxide and less oxygen, because plant roots and soil organisms continuously use oxygen for respiration and release carbon dioxide. The oxygen in soil air is critical for two reasons:
\n\nRoot respiration: Plant roots need oxygen to carry out cellular respiration, which provides the energy they need to absorb water and nutrients. If roots are deprived of oxygen (as in waterlogged soil), they cannot function properly, and the plant wilts and may die.
\n\nSoil organisms: Bacteria, fungi, earthworms, and other organisms that decompose organic matter and recycle nutrients also require oxygen. Without adequate soil air, these organisms cannot do their work, and nutrient cycling slows down.
\n\nSandy soils tend to have more air because their large pore spaces are not filled with water for long. Clay soils tend to have less air because water is held tightly in the small pore spaces. Farmers can improve soil aeration by adding organic matter, avoiding compaction from heavy machinery or livestock trampling, and practising tillage to loosen compacted soil layers.
\n\nHow Proportions Change
\n\nThe proportions of water and air in soil are not fixed , they change depending on conditions. After heavy rainfall, such as during Malawi’s rainy season, the proportion of water increases while the proportion of air decreases. In extreme cases, the soil becomes waterlogged (nearly all pore spaces filled with water), which is harmful to most crops except rice, which is adapted to flooded conditions in areas like the Bua and Lifidzi river valleys. During the dry season, the opposite happens: the proportion of water decreases and the proportion of air increases. Very dry soil can become so hard and compacted that roots struggle to grow, which is why mulching and irrigation are important practices for farmers in Malawi.
\n\nUnderstanding soil composition helps farmers make better decisions. A farmer who knows that their sandy soil drains too quickly can add organic matter to improve water retention. A farmer with heavy clay soil can add organic matter and sand to improve drainage and aeration. By managing all four soil components wisely, Malawian farmers can create the best possible conditions for their crops to thrive.
Nthawi: Mphindi 40
\n\nDothi ndi chimodzi mwa zinthu zofunikira kwambiri zachilengedwe pa ulimi ku Malawi. Ngakhale mukulima chimanga ku bwalo la Central Region ku Lilongwe, mukulima fodya ku Kasungu, kapena mukulima masamba m’mphepete mwa Nyanja ya Malawi, kupambana kwa mbewu zanu kumadalira dothi lomwe lili pansi. Koma kodi dothi limapangidwa ndi chiyani kwenikweni? Dothi si chinthu chimodzi , ndi chosakaniza cha zinthu zinayi zazikulu: madite a miyala, zinthu zaumoyo (chinyezi), madzi, ndi mpweya. Kumvetsetsa zinthu izi ndi momwe zimagwizirana ndi kofunikira kwa alimi onse ndi ophunzira za ulimi.
\n\nMadite a Miyala (pafupifupi 45% ya dothi)
\n\nMadite a miyala ndi gawo lalikulu kwambiri la dothi. Amapangidwa ndi tizinthu tating’onoting’ono tomwe timachokera pakusweka kwa miyala kwa zaka zambirimbiri. Miyala imasweka ndi mphamvu za chilengedwe monga kusintha kwa kutentha, mphepo, ndi madzi, komanso ndi zochitika za mankhwala a mu chilengedwe. Tizinthu ting’onoting’ono timene timatuluka timasiyana kukula kwake, ndipo kukula kumeneku ndiko kumatsimikiza mtundu wa dothi. Pali mitundu itatu ya madite a miyala:
\n\nMchenga (Sand): Tizinthu talikulu kwambiri (0.05-2.0 mm). Mchenga umamveka ngati tizinthu todzadzamira mukaugwedeza pakati pa zala. Dothi la mchenga, lomwe limapezeka m’mbali mwa Shire Valley ndi m’mphepete mwa nyanja, lili ndi malo akulu pakati pa tizinthu, zomwe zimatanthauza kuti madzi amadutsa msanga ndipo mpweya umalowa mosavuta. Komabe, dothi la mchenga limasunga zakudya zochepa chifukwa madzi amasukutsa zakudya zakezo.
\n\nSiliti (Silt): Tizinthu ta pakati (0.002-0.05 mm). Siliti imamveka yosalala ngati ufa. Siliti imasunga madzi ndi zakudya bwino kuposa mchenga koma osati bwino ngati dongo.
\n\nDongo (Clay): Tizinthu tating’onoting’ono kwambiri (tochepera 0.002 mm). Dongo limamveka lomatira likanyowa ndipo limaumba zipande zolimba likawuma. Dothi la dongo limasunga madzi ndi zakudya zambiri chifukwa tizinthu tating’ono timayandikirirana, ndipo timapanga malo ang’onoang’ono kwambiri. Komabe, dothi la dongo lingathe kudzaza ndi madzi kwambiri ndipo mizu ingathe kulephera kulowamo. Dothi m’madambo ambiri a ku Malawi ndi la dongo.
\n\nDothi la ulimi lambiri ku Malawi ndi chosakaniza cha mchenga, siliti, ndi dongo, chomwe chimatchedwa lomu. Dothi la lomu limaonedwa ngati labwino kwambiri pa ulimi chifukwa limabalansira kusunga madzi, kutayira madzi, kupeza mpweya, ndi kusunga zakudya.
\n\nZinthu Zaumoyo / Chinyezi (pafupifupi 5% ya dothi)
\n\nZinthu zaumoyo zimapangidwa ndi zotsalira za zomera ndi nyama zomwe zawola. Pamene masamba, mizu, zotsalira za mbewu, ndowe, ndi zamoyo zakufa zimasweka chifukwa cha ntchito ya tizilombo monga bakiteriya, bowa, njoka za pa dothi, ndi zinthu zina zamoyo, zimapanga chinthu chakuda chosalala chotchedwa chinyezi. Ngakhale kuti zinthu zaumoyo zimapanga 5% yokha ya dothi, kufunika kwake pa ulimi ndi kwakukulu:
\n\nChinyezi chimapititsa patsogolo kupangidwa kwa dothi mwa kumangiriza tizinthu pamodzi, zomwe zimapanga malo a mpweya ndi madzi.
\n\nChimawonjezera kuthekera kwa dothi kusunga madzi, zomwe ndizofunikira kwambiri nyengo yachilimwe ku Malawi pamene mbewu zimavutika ndi kusowa madzi.
\n\nChinyezi chimapereka zakudya zofunikira za mbewu monga nitrogen, phosphorus, ndi sulphur pomwe chimapitilira kuwola.
\n\nChimapereka chakudya ndi malo okhala kwa tizilombo za m’dothi monga njoka za pa dothi, zomwe zimapititsa patsogolo kupangidwa bwino kwa dothi kudzera mukumbira kwawo.
\n\nAlimi ku Malawi angathe kuwonjezera zinthu zaumoyo m’dothi lawo mwa kuwonjezera zotsalira za mbewu (monga mapesi a chimanga ndi makoko a mtedza), kuthira komposti kapena ndowe, ndi kulima mbewu zobiriwitsira dothi monga Tephrosia vogelii kapena sun hemp.
\n\nMadzi a m’Dothi (pafupifupi 25% ya dothi)
\n\nMadzi amakhala m’malo opanda kanthu pakati pa tizinthu ta dothi. Si madzi oyera koma ndi solushoni ya m’dothi , madzi okhala ndi zakudya za ma mineralo zosungunuka monga nitrogen, phosphorus, potassium, calcium, ndi magnesium. Mizu ya mbewu imamwa zakudya zosungunukazi kuchokera mu solushoni ya m’dothi kudzera mu njira yotchedwa osmosis. Popanda madzi a m’dothi, mbewu sizingathe kupeza zakudya zomwe zikuzifuna, ngakhale dothilo ndi lolemera ndi zakudya.
\n\nKuchuluka kwa madzi omwe dothi lingathe kusunga kumadalira mtundu wake. Dothi la dongo limasunga madzi ambiri chifukwa tizinthu take tating’ono timapanga malo ochepa kwambiri. Dothi la mchenga limasunga madzi ochepa chifukwa malo ake aakulu amalola madzi kudutsa msanga. Pa nyengo yamvula ku Malawi (November mpaka April), dothi lingathe kudzaza kwathunthu ndi madzi, makamaka m’malo otsika ndi m’madambo. Dothi likadzaza ndi madzi, madzi amadzaza malo onse opanda kanthu, kuthamangitsa mpweya ndipo kumapsa mizu ya mbewu.
\n\nMpweya wa m’Dothi (pafupifupi 25% ya dothi)
\n\nMpweya umadzaza malo opanda kanthu m’dothi omwe sadzazidwa ndi madzi. Mpweya wa m’dothi uli ndi zinthu zofanana ndi mpweya wa m’mlengalenga koma uli ndi carbon dioxide yochuluka ndi oxygen yochepa, chifukwa mizu ya mbewu ndi tizilombo za m’dothi zimagwiritsa ntchito oxygen pa kupuma ndi kutulutsa carbon dioxide nthawi zonse. Oxygen wa m’dothi ndi wofunikira pa zifukwa ziwiri:
\n\nKupuma kwa mizu: Mizu ya mbewu imafunikira oxygen kuti ichite kupuma kwa maselo, komwe kumapereka mphamvu yomwe imafunikira kumwa madzi ndi zakudya. Ngati mizu ilibe oxygen (monga m’dothi lodzaza ndi madzi), singagwire ntchito bwino, ndipo mbewezo zimafota ndipo zingathe kufa.
\n\nTizilombo za m’dothi: Bakiteriya, bowa, njoka za pa dothi, ndi tizilombo tina tomwe timawola zinthu zaumoyo ndi kubwezeretsa zakudya timafunikiranso oxygen. Popanda mpweya wokwanira m’dothi, tizilombo izi sizingathe kugwira ntchito yawo, ndipo kuzungulira kwa zakudya kumachepa.
\n\nDothi la mchenga likhoza kukhala ndi mpweya wochuluka chifukwa malo ake aakulu sadzazidwa ndi madzi nthawi yayitali. Dothi la dongo likhoza kukhala ndi mpweya wochepa chifukwa madzi amasungidwa mwamphamvu m’malo ang’onoang’ono. Alimi angathe kupititsa patsogolo mpweya wa m’dothi mwa kuwonjezera zinthu zaumoyo, kupewa kupondana kwa dothi, ndi kulima kuti atambasule malata a dothi oumba.
\n\nMomwe Kuchuluka Kumasinthira
\n\nKuchuluka kwa madzi ndi mpweya m’dothi sikukhazikika , kumasintha malingana ndi nyengo. Mvula ikagwa kwambiri, monga pa nyengo yamvula ku Malawi, kuchuluka kwa madzi kumaonjezeka pomwe kuchuluka kwa mpweya kumachepa. Nyengo yachilimwe, zosiyana zimachitika: madzi amachepa ndipo mpweya umaonjezeka. Dothi louma kwambiri lingathe kukhala lolimba ndi lopondana kwakuti mizu imalephera kukula, ndiye chifukwa chake kuphimbira ndi mathkhedwe a kuthirira ndi njira zofunikira kwa alimi a ku Malawi.
\n\nKumvetsetsa zopangira dothi kumathandiza alimi kupanga zisankho zabwino. Mlimi wodziwa kuti dothi lake la mchenga limasefukira msanga angathe kuwonjezera zinthu zaumoyo kuti apititse patsogolo kusunga madzi. Mlimi wokhala ndi dothi la dongo lolimba angathe kuwonjezera zinthu zaumoyo ndi mchenga kuti apititse patsogolo kusefukira ndi mpweya. Mwa kusamalira zinthu zinayi za dothi mwanzeru, alimi a ku Malawi angathe kupanga malo abwino kwambiri kuti mbewu zawo zikule bwino.
Exercise RequiredMasewera Ofunikira
You must pass this exercise to complete the lesson. Questions are randomly selected each attempt. Muyenera kupambana masewera awa kuti mumaliza phunziro. Mafunso amasankhidwa mwachisawawa nthawi iliyonse.