ALLIED MARKETS - LET’S COVER THE SOIL WITH LIME

Elena KORCHINSKAYA, the Agrarian Economics Institute with the Ukrainian Academy of Agrarian Sciences

Yield is the main figure of efficient soil fertility. Studies show that its enhancement is strongly influenced not only by sufficient watering of soils and nutrient value, but also by the reaction of soil medium.

Most agricultural crops demand subacid or neutral reaction for their growth and development. Alfalfa, sugar beets, mangelwurzel, and cabbages are especially sensitive to soil acidity. That is why they grow well only on neutral and low-alkalinity soils, e.g. with рН equaling 6.1 to 8. Such crops as wheat, barley, corn, peas, beans, clovers, onions, cucumbers, and sunflowers are also sensitive to excessive acidity. They need subacid and close to neutral reaction, e.g. рН of 5.1 to 6.

Soils with excessive acidity contain substances, which are harmful for plants (Al, Mn, F), and give poorer yields even provided sufficient amount of nutrients. In acid soils, growth and ramification of roots slows down, while application of soil nutrients and fertilizers, which are crucially important for normal vital functions, is hampered.

In Ukraine the areas of high-acidity arable lands make up about 10,000,000 hectares (30% of the total tillage). There are more than enough acid soils in marshy woodlands and forest-steppe zones, in other words, in cultivation areas for sugar beet (the crop that is truly sensitive to acidity). In such regions as Zakarpatye and Ivano-Frankovsk, acid soils account for 70% of the total, in Chernigov, Zhitomir, Vinnitsa, Kirovograd, Poltava, Sumy, Kherson, and Cherkassy regions for more than 50%.

Liming is one of the most important ways to enhancement of acid soils' productivity. Lime is a powerful means of soil melioration, which changes radically physical and chemical properties of soil.

Lime is not only the soil improvement instrument, but also the source of calcium. Clover, alfalfa, sugar beet, mangelwurzel, cabbage, mustard, etc. experience shortage of calcium most often. Liming of acid soils provides this necessary nutrient, increases effectiveness of mineral and organic fertilizers, improves the vital functions of useful microorganisms, physical properties and structure of soils.

Application of optimal doses of lime increases the average yields by up to 5.5 centners per hectare for winter wheat, by 9 centers/ha for corn (grain value), by 20 centners/ha for potatoes, by 50 centners/ha for sugar beet, and by 10 centners/ha for hay of perennial grasses.

Lime fertilizers boost the yields, as well as enhance the quality of agricultural produce, notably they increase vitamin contents in grain, hay, and silage; boost sugar contents in edible roots; add some 30-40% to proteins contents in winter wheat; and about 3-5% to starch contents in potatoes. Birth rate increases and morbidity rate goes down when livestock animals are fed with calcium-rich fodder.

It is also worth mentioning the radiation protection function of lime. Migration of radionuclides from soil to plants reduces significantly under the influence of liming. Full-scale standard application of lime (the average of 7 tonnes of lime per hectare in Ukraine) reduces strontium and cesium contents in plants 1.2-2 times or even 3 times in specific cases.

As a way to improve fertility of acid soils, liming has been applied in agriculture for ages. Information about this process can be found in the antique literature of the Roman age. For instance, in his books, Pliny the Elder writes about application of lime to fertilize vineyards, oilseed and cherry plantations. Liming was widespread in Western European countries. Back in the 17^th century in England, lawyer Sir A. Fitzgerbet recommended use of lime and marl as fertilizers in his first agricultural writing work. In the mid-18^th century, there were published the works on liming of soils written by famous French scientist Duhamel. In the first half of the 19^th century, the Germans linked their achievements in agriculture with application of marl in farming.

In Ukraine, the All-Russian Association of Sugar Refiners initiated the experiments on application of lime in the sugar-beet cultivation region back in 1900. Nevertheless, chemical soil melioration efforts were rather limited prior to 1965. Starting 1966, the volumes of liming have increased considerably (see table 1).

Figures	Years
Figures	1961-1965	1966-1970	1971-1975	1976-1980	1981-1985	1986-1989
Area limed (‘000 hectares)	393.3	1,186.5	1,310.5	1,262.2	1,462.2	1,564.0
Lime applied (‘000 tonnes)	1,228.4	4,379.4	4,662.5	4,712.4	5,888.4	7,993.0

For example, 5,933,100 hectares of acid soils were limed in the period of 1966-1970. In the subsequent years, the liming rates increased year-on-year, and 1,500,000 ha of acid soils were limed in 1989. The total area limed in 1966-1989 amounted to 32,200,000 ha. Some 130,500,000 tonnes of lime-based substances were spread on the fields.

The liming efforts applied to acid soils resulted in the increase in soil fertility figures (see table 2).

Round of inspection	Year	High-acid soils	Medium-acid soils	Subacid soils	Neutral and close to neutral soils
I	1966-1970	6.1	12.8	15.5	65.6
II	1971-1975	3.8	8.5	14.2	70.4
III	1976-1980	2.5	8.0	17.4	70.0
IV	1980-1985	2.2	7.2	17.4	71.2
V	1986-1990	1.8	6.7	17.2	72.4
VI	1991-1995	2.6	7.7	18.9	70.8

The figures in table 2 demonstrate that the area of high-acid soils reduced 3.2 times during the period under review, area of medium-acid lands lost 1.8 times, and area of neutral and close to neutral soils increased 1.2 times. The qualitative changes in soil fertility have exerted positive influence on crop yields (see table 3).

	1966-1970	1971-1975	1976-1980	1981-1985	1986-1989
Cereals	21.4	24.8	26.1	24.3	29.5
Winter wheat	23.6	28.4	30.3	27.5	35.6
Corn (grain value)	27.9	27.9	29.0	30.1	33.1
Sugar beet	266.0	267.7	300.9	258.4	282.6

Tables 1, 2, and 3 show that the change of soil fertility and crop yields directly depend on the scope of chemical melioration efforts on acid soils.

Chemical improvement of soils in Ukraine is carried out mainly at the expense of the state budget. In recent years, the volumes of chemical soil melioration have been shrinking due to financial difficulties. For instance, in 1998, only UAH 4,000,000 out of the required UAH 207,000,000 were allocated for chemical soil melioration, i.e. covering about 2% of the demand. As a result, lime was applied to 32,700 hectares, whereas it is necessary to lime 1,800,000 hectares of acid soils every year. The volume of applied lime amounted to 208,300 tonnes. In 1999 the situation with chemical soil improvement measures worsened some more (see table 4).

Figure	Year
Figure	1990	1991	1992	1993	1994	1995	1996	1997	1998	1999
Area limed (‘000 hectares)	1,439	1,406	1,084	447	288	268	123	34.7	32.7	23.0
Lime applied (‘000 tonnes)	7,372	7,138	5,344	2,324	1,521	1,420	652	205	208	163

Curtailment of the chemical melioration scope leads to unfavorable economic and ecological consequences. Today, non-limed areas lose more than 1,000,000 tonnes of crop produce (grain value) per year. Agro-chemical researches show that there is a trend towards more acid soils (see table 2). In future, excessive soil acidity will make it impossible to cultivate agricultural crops that are sensitive to acid reaction of soils, notably sugar beet, winter wheat, barley, perennial grasses, and other crops.

One of the reasons of higher soil acidity is the application of physiologically acid mineral fertilizers, especially the nitrogenous ones. It takes 1 to 1.5 lime units to neutralize these fertilizers. Nowadays, the ratio of nutrients in mineral fertilizers applied equals to N/P/K=1/0.2/0.1, i.e. there is a huge disproportion in favor of nitrogenous fertilizers. In the current situation, when there is no liming, application of such ratios of mineral fertilizers can turn from a favorable factor, which enhances productiveness of tillage and yields of agricultural crops, into an adverse factor and can have exactly the opposite effect. The rates of liming should outrun the rates of application of mineral fertilizers. It adds some 20 to 30% to fertilizers' efficiency and slashes overhead costs. Liming of soils makes it possible to get higher yields with considerably lower (by 25 to 30%) consumption of mineral fertilizers, which contributes to weighty saving of scarce resources. Besides, it seems rational to apply complex fertilizers, which contain calcium and magnesium along with nitrogen, phosphorus, and potassium. Foreign experience shows that ammonium nitrate, which causes acidulation, should be replaced with lime-ammonium nitrate, which can be obtained through neutralization of ammonium nitrate with chalk, lime, or dolomite. Lime-ammonium nitrate is an extremely valuable fertilizer on acid soils, notably, for such acidity-sensitive crops as beet, winter wheat, and clover. This explains the popularity of this kind of fertilizers in the developed countries.

Up to the middle of the 1990es, twenty Ukrainian enterprises supplied lime-based substances to agriculture. Today, during the recession in output of land-improving substances, increase in application costs, especially in freightage rates for delivery from industrial enterprises, and financial hardships of agricultural companies, it is necessary to make wider use of local carbonate deposits. These deposits are found in 15 regions with the total mineral inventories reaching more than a billion tonnes. Such deposits exist in almost all the regions with widespread occurrence of acid soils. For instance, Kharkov region is rich in supplies of chalk and limestone, which frequently outcrop and, therefore, can be quarried. Mineral inventories of dolomites in, let's say, Negribov deposit of Zhitomir region equal 160-180 million tonnes.

In the forest-steppe zone, farms and agro-firms, located close to sugar refineries, can improve soil with beet-sugar refining waste, namely with defecator that contains up to 70% of СаСО₃, 0.3-0.5% of N, 1-2% of P₂O₅, 0.6-0.9% of K₂O, and up to 15% of organic substance. There are about 170 sugar refineries located in Ukraine. Only in Kiev region, there are 16 such refineries that can produce 300,000 to 350,000 tonnes of high-quality defecator per year. Application of defecator not only increases the crop yields (by 20-40 centners per hectare for sugar beet, 5-7 centners/ha for winter wheat, up to 10 centners/ha for perennial grasses), but also boosts sugar contents in sugar beet by 0.2-0.4%.

It should be also noted that lime-based substances are the cheapest among fertilizers, since in most cases they are nothing but manufacturing refuse. Their application ensures positive effect of lime during 5-to 20 years depending on the dose applied and mechanical structure of soil. That is why application of lime yields UAH 3-6 of net income per UAH 1 of costs depending on soils.

Thus, radical improvement of chemical soil melioration efforts, which requires relatively moderate investment, will make it possible to boost gross crop yields by 15-20%, to increase economic efficiency of agricultural production, and to set the real prerequisites for stable progress of expanded reproduction of soil fertility.

Reference note. Last time, research on soil acidity was held in Ukraine back in 1996. New research is scheduled for 2000 with participation of the Ministry for Agrarian Policy, the State Committee for Land Resources, and the Center for Land Fertility.


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