How fertile are soils of our farms for optimum crop yield?
IN part one of this write-up (published on Nov 11), we discussed the synergistic effects of physical, chemical, and biological properties of on soil and crop productivity.
As a follow of part one of this article, we will briefly touch on very important soil chemical properties such pH and aluminium and iron toxicity, an aspect has a very limiting effect on soil quality and overall plant growth and development on mineral acid soil globally (including Malaysia).
Afterwards, a practical example as how one can harness the three soil chemical properties to impact crop yield with significant economic will be demonstrated.
Another soil chemical property which affects soil fertility is pH. Soil pH indicates how acidic or basic soils are.
Strong acid soils are soils with pH less than five, moderate acid soils are soils whose pH range between 5 and 6.5, and neutral to alkaline soils are noted for having a pH of 7 or more.
In both acidic and basic (alkaline) soils, the survival of plants and organisms (including very tiny organisms) are affected, suggesting that soil pH also plays an essential role in soil and crop productivity.
In fact, to some extent, soil pH does not only determine the distribution or occurrence of vegetation and organisms, but it can also control the type of crops to be grown within a locality, country, region, continent, and the world.
Although soil pHis familiar and sounds simple, it is imperative that farmers pay serious attention to this important soil chemical property because if it is not well managed, soil and crop productivity could low and this will surely reduce the crop economic yield of most crops and one of the ripple effects is low income of farmers regardless of their toil.
The world map be shows the worldwide occurrence of acid and alkaline soils.
Because the subject matter of this write-up focuses on Malaysia, the subsequent discussion is limited acid soils. Notice in the world map (picture 1) that almost all of the soils in Malaysia are acidic because their pH are below 7.
In terms of pH and according to the world map on soil pH, Malaysian soils could be categorised as strong to moderate acid soils.
This suggests that the agronomic and economic potential of soils of this kind are realised by correcting their acidity via for instance, liming.
Otherwise, farmers may toil in vain because of this limiting factor.
Another soil chemical property which is closely related to soil pH is iron and aluminium contents in soils.
Literally, when they are active, their activities (hydrolysis) lead to production of more hydrogen ions to make soils more acidic.
Apart from this, higher contents of iron and aluminium or toxic level of these ions adversely affect the soil fertility of most soils.
Higher content of iron in soils makes such soils toxic to plant roots in particular besides making such soils appear reddish.
As shown in the picture (2), the red spots indicate rusting of iron in the soil.
These red spots can be toxic to the overall growth and development of crops.
If the high iron content is not properly managed, the red spots due to rusting of iron could spread uniformly in soils.
The picture (3) shows the spread of iron. If farmers are to remain in business, the elevated iron distribution in their farms could cost them huge sums of money to fix iron toxicity.
In some cases, this can be frustrating as little or poor knowledge on managing soil pH, iron, and aluminium may end farmers’ effort in futility. As shown in the world map
(picture 4), most of the Malaysian soils are also high in aluminium and this should never be overlooked as excessive aluminium in soils has devastating effects on plant roots and other soil organisms.
Another adverse effect of the high contents of iron and aluminium in soils is that they commonly prevent significant amount of phosphorus in particular from being taken up by plants through root absorption.
This process of iron and aluminium preventing phosphorus from being efficiently taken up by plants is called phosphorous fixation. If this negative process is which is a global challenge is permanently solved in Malaysia, besides farmers saving significant amount of money on phosphorus fertilizers (triple superphosphate, rock phosphates etc.), optimum yield which translates into increased economic gain could be achieved.
Such innovation or intervention could partly contribute to reduction of the fertilizer import of Malaysia as Malaysia is one of the countries which uses significant amounts of chemical fertilisers.
Phosphorus fixation by iron and aluminium can be a serious setback in most farming systems because phosphorus plays very important role in keeping plant roots healthy.
Healthy plants roots ensure that other nutrients such as nitrogen, potassium, calcium, magnesium, and water are absorbed and transported to other parts of plants.
Conventionally, farmers tend to focus more on correcting soil chemical properties using chemical fertilizers and liming, thinking such approach is the most appropriate way of rejuvenating soil productivity.
The defects of this approach is that, it is not only a temporary solution but it also not holistic and sustainable a practice.
For instance, liming an acid soil using calcium carbonate or dolomite which are all chemical or inorganic materials is not only a transient measure but it also does not significantly improve most of the soil physical and chemical properties discussed in part one of this write-up.
In fact, unbalanced use of chemical inputs such as chemical fertilizers rather degrades soil quality or health apart from causing soil, water, and air pollution.
To some extent, algae bloom of water bodies which are closer to farming areas is partly related poor management of nitrogen and phosphorus whereas excessive and continued used of nitrogen fertilizers such as ammonium sulphate causes soil acidity.
In fact, continued use of some sodium based fertilizers can destroy structure through dispersion of soil particles (sand, silt, clay, and soil organic matter).
This is because salts of sodium are dispersing agents and they can break clays and other soil particles from sand.
If the use of nitrogen fertilisers such as ammonium nitrate, urea, and so forth are not well controlled in agriculture, significant release of ammonia from these nitrogen fertilizers into the atmosphere instead the nitrogen of their nitrogen being used by plants will not only cause air pollution and the economic loss in terms of poor crop yield cannot be over emphasized.
Improper use of liming materials to correct soil acidity and iron and aluminium toxicity could also create another adverse effect such as copper and zinc deficiencies.
Over liming could also cause out of range soil pH. Such out of range soil pH may be unsuitable for intended crops for which soil liming process was carried out.
From the foregoing discussion, it is clear that we can longer narrow or limit our understanding of how fertile soils are to only the chemical properties of soils.
Moreover, the problem with such restricted understanding is that it is further confined to plant nutrients, no wonder fertilizers are used by a number of farmers as the first line for mitigating or redeeming soil fertility.
We being cognizant of the interrelatedness of soil physical, chemical, and biological properties soils coupled with their synergism, we have produced organic amendments from unwanted agricultural wastes which able to improve soil and crop productivity as well as the economic income of several rice growers.
Our innovation is rooted in the fundamental understanding of ‘a sound mind lives in a sound body’.
To this end, we have transformed agro-wastes into activated organic amendments which are able condition the afore-discussed three major soil components (physical, chemical, and biological) such that crop and soil productivity are enhanced.
The picture (5) shows a comparison between our intervention which detoxifies soils from iron and aluminium as well as enhancing soil pH and other soil chemical, physical, and biological properties.
This is why the soil colour with our intervention looks greyish (T3) whereas the colour of the soil without our intervention looks yellowish (T2).
The greyish colour following our innovation suggests the soil had been rejuvenated (conditioned or detoxified) whereas the soil in the plot showing yellow coloration indicates poor soil quality.
This difference explains why the rice growth looks better with our approach (T3) compared with the existing practice of cultivation rice (T2).
Our intervention had also been tested in rice cultivation in a number of locations in Malaysia and the rice growers who are currently patronising our innovation are realising good yield and significant profit margins.
The pictures (6) show vigorous growth of rice plants of some of our rice farmers in Malaysia.
In conclusion, sustainable soil and crop productivity requires good understanding of how soil physical, chemical, and biological properties interact to maintain soil quality.