How fer­tile are soils of our farms for op­ti­mum crop yield?

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That be­ing the case, bal­anced in­ter­ac­tions among soil prop­er­ties or how well the prop­er­ties are man­aged, es­pe­cially by farm­ers in­clud­ing plan­ta­tions could de­ter­mine how fer­tile or in­fer­tile a soil is or will be.

In a sim­ple lan­guage, soil phys­i­cal prop­er­ties are the char­ac­ter­is­tics of any soil which can be gen­er­ally seen and felt by any­one in­clud­ing farm­ers, although some prop­er­ties are con­firmed in lab­o­ra­tory anal­y­sis.

Some of the ex­am­ples of soil phys­i­cal prop­er­ties are soil tex­ture, soil struc­ture, soil colour, and so on.

Soil tex­ture is the pro­por­tion of sand, silt, and clay. On the other hand, the ar­range­ment of sand, silt, and clay to en­sure some de­gree of the sta­bil­ity of th­ese par­ti­cles to prevent for in­stance, soils from col­laps­ing is re­ferred to as soil struc­ture.

Soil tex­ture can eas­ily in­di­cate how sandy or clayey soils are or it could sug­gest how chal­leng­ing it will be to man­age such soils.

On the other hand, how loose or dense (com­pact) such soils are is partly con­trolled by soil struc­ture.

There­fore, the na­ture of the com­po­si­tion of soil par­ti­cles and their ag­gre­ga­tion (soil tex­ture and struc­ture) play es­sen­tial role in de­ter­min­ing for ex­am­ple, how well wa­ter is dis­trib­uted in soils, how much wa­ter and nu­tri­ents soils can hold, how fast or slow wa­ter and air can move in soils, how fast wa­ter can pen­e­trate (in­fil­trate) soils dur­ing and af­ter rain fail or ir­ri­gation, how much wa­ter runs through and out of soils (leach­ing), and how wa­ter can run on and from soils’ sur­face (runoff).

Soil phys­i­cal prop­er­ties can also con­trol plant root res­pi­ra­tion (breath­ing of plants), move­ment of roots, up­take, trans­mis­sion, and dis­tri­bu­tion of wa­ter and nu­tri­ents by roots.

They also in­flu­ence the liv­ing con­di­tions/en­vi­ron­ment of or­gan­isms which are not seen with naked hu­man eyes (ex­am­ple, ne­ma­todes, bac­te­ria, fungi, viruses, and so on) or can be seen with naked hu­man eyes (ter­mites, earth­worms, ro­dents, and so on).

Although soil phys­i­cal prop­er­ties are im­por­tant in agri­cul­ture, their role vis a vis soil fer­til­ity is not ex­clu­sive from other cat­e­gories of soil char­ac­ter­is­tics be­cause as an ex­am­ple, ag­gre­ga­tion of soil par­ti­cles to form good soil struc­ture to en­able good plant growth and de­vel­op­ment needs lit­er­ally, a ‘spe­cial glue’ called soil or­ganic mat­ter which holds/ce­ments sand, silt, and clay to­gether such that such a soil has good spa­ces for crops and or­gan­isms to thrive.

It must be noted that soil or­ganic mat­ter comes from de­com­po­si­tion or break­down of dead plants ma­te­ri­als, an­i­mals, and other liv­ing and non-liv­ing or­gan­isms.

How fast or slow soil or­ganic mat­ter forms in soils is partly con­trolled by soil phys­i­cal prop­er­ties such as tex­ture and the ac­tiv­i­ties of very tiny or­gan­isms such as bac­te­ria and fungi and also big­ger or­gan­isms such as earth­worms, in­sects, root ex­u­dates, and so forth.

The in­volve­ment of or­gan­isms to pos­i­tively or neg­a­tively im­pact soil qual­ity or health is known as soil bi­o­log­i­cal prop­er­ties and this is shown in the pic­ture be­low where or­gan­isms in­ter­act with the soil.

Among the pos­i­tive in­ter­ac­tions is bor­row­ing soils by ro­dents (rats, mice) and earth­worms to cre­ate chan­nels (holes) for wa­ter, air, and nu­tri­ents trans­mis­sion and one of the neg­a­tive in­ter­ac­tions is plant root de­struc­tion by ne­ma­todes and fungi.

Note that soil or­ganic mat­ter is one of ex­am­ples of soil chem­i­cal prop­er­ties.

This means that good soils should have some rea­son­able amount of or­ganic mat­ter to en­sure such soils are less com­pact to some ex­tent that good amount of wa­ter can be held and sup­plied to plants for use.

This soil wa­ter should also be able to trans­port nu­tri­ents (food of plants) timely with­out the nu­tri­ents be­ing lost from the soil or locked up in the soil.

The or­ganic mat­ter also fa­cil­i­tates the in­flow and out­flow of oxy­gen in soils to en­sure that plants and other or­gan­isms have ad­e­quate amount of oxy­gen for their daily ac­tiv­i­ties just as in hu­man be­ings.

The right amount of or­ganic mat­ter also en­sures good soil tem­per­a­ture to avoid ex­ces­sive heat which could kill or de­stroy plant roots and other or­gan­isms in soils.

Cer­tainly, soils with good or­ganic mat­ter makes such soils rea­son­ably loose to boost the ac­tiv­i­ties of liv­ing or­gan­isms.

For such soils, rain wa­ter as an ex­am­ple, can eas­ily pen­e­trate or in­fil­trate them to avoid too much of wa­ter be­ing lost from their sur­faces to cause flood­ing or wash­ing away of seeds, fer­til­iz­ers, pes­ti­cides, weed­i­cides, and her­bi­cides.

Wa­ter dis­tri­bu­tion in soils with rea­son­able or­ganic mat­ter is good be­cause soil or­ganic mat­ter lit­er­ally acts like a sponge to timely ab­sorb and re­lease wa­ter.

More­over, soil or­ganic mat­ter sig­nif­i­cantly im­proves the amount of nu­tri­ents soils can hold from for ex­am­ple, fer­til­iz­ers.

From eco­nomic point of view, suf­fi­cient amount of soil or­ganic mat­ter will not only save farm­ers from los­ing fer­til­iz­ers but it will also en­able farm­ers to make good money from good har­vest be­cause ef­fi­cient use of fer­til­iz­ers and re­lated farm in­puts are guar­an­teed to in­crease crop yield and profit mar­gin. Fur­ther­more, the soil or­ganic mat­ter it­self is rich in plant nu­tri­ents such as ni­tro­gen, potas­sium, phos­pho­rus, cal­cium, mag­ne­sium, and so on, thus it could com­pli­ment nu­tri­ents from chem­i­cal fer­til­iz­ers.

Ad­di­tion­ally, be­cause soil or­ganic mat­ter are made up of neg­a­tive charges, they are very good in at­tract­ing and stor­ing pos­i­tively charges nu­tri­ents such as potas­sium, am­mo­nium, cal­cium, mag­ne­sium, cop­per, and zinc fer­til­iz­ers or limes from be­ing lost from farms.

The abil­ity of soils to hold or store and re­lease pos­i­tive nu­tri­ents for plants to use is called cation ex­change ca­pac­ity (CEC). Soil clays are also able to at­tract and hold pos­i­tive charges just like soil or­ganic mat­ter although soil or­ganic mat­ter holds more pos­i­tive charges than clays.

Based on the neg­a­tive charges which are con­trib­uted by both the phys­i­cal and chem­i­cal as­pects of soils, we can now ap­pre­ci­ate that both soil phys­i­cal and chem­i­cal prop­er­ties in­ter­ac­tion to con­trol the use nu­tri­ents by plants, there­fore one can say that both soil phys­i­cal and chem­i­cal prop­er­ties con­trib­ute to soil fer­til­ity.

With the ba­sic un­der­stand­ing of what soil fer­til­ity is, part two of this ar­ti­cle dis­cusses how soils could be man­aged for op­ti­mum crop yield with good eco­nomic re­turns.

PROF DR AHMED OSUMANU HARUNA

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