Thirty years of growing cereal without P and K fertilization

Over thirty years a significant depletion of P and K in soil occured when the were not given in fertilizers. This caused a reduction in crop yield. An abundant P application exceeding the crop uptake very clearly prevented the yield reduction but did not raise the extractable P concentration in the soil. Severe K deficiency did not start to appear until 20 years of growing cereal without fertilizer K. K application compensating for the uptake by the crop did not prevent the decrease of its extractable concentration in this soil, but this decrease did not affect crop yield

Viljelymaan sinkkivarojen ja lannoitteena annetun sinkin käyttökelpoisuus kasveille

The Zn status of cultivated soils of Finland was investigated by chemical analyses and bioassays. The effect on ryegrass of different Zn fertilizers and Zn rates was studied in pot experiments and their effect on barley and timothy in field experiments. In an uncontaminated surface soil material of 72 mineral soils and 34 organogenic soils, total Zn (Zntot) was 10.3-202 mg kg-1(median 66 mg kg-1). In mineral soils, Zntot correlated positively with clay content (r = 0.81***) and in organogenic soils negatively with organic C (r = -0.53***). Zinc bound by organic matter and sesquioxides was sequentially extracted by 0.1 M K4P2O7 (Znpy) and 0.05 M oxalate at pH 2.9 (Znox), respectively. The sum Znpy + Znox, a measure of secondary Zn potentially available to plants, was 2 - 88% of Zntot and was the lowest in clay (median 5%) and highest in peat soils (median 49%). Water-soluble and exchangeable Zn consisted of0.3 - 37% (median 3%) of Zntot, the percentage being higher in acid soils, particularly in peat soils. Zinc was also extracted by 0.5 M ammonium acetate - 0,5 M acetic acid - 0.02 M Na2-EDTA at pH 4.65 (ZnAC), the method used in soil testing in Finland. The quantities of ZnAC (median 2.9 mg dm-3, range 0.6 - 29.9 mg dm-3) averaged 50% and 75% of Znpy + Znox in mineral and organogenic soils, respectively, and correlated closely with Znpy. In soil profiles, ZnAC was with few exceptions higher in the plough layer (0 - 20 cm) than in the subsoil (30 - 100 cm). In an intensive pot experiment on 107 surface soils, four crops of ryegrass took up 2 - 68% (median 26%)of Znpy + Znox. The plant-available Zn reserves were not exhausted even though in a few peat soils the Zn supply to grass decreased over time. Variation of Zn uptake was quite accurately explained by ZnAC but increasing pH had a negative impact on Zn uptake. Application of Zn (10 mg dm-3 of soil as ZnSO4 * 7 H2O) did not give rise to yield increases. In mineral soils, increase of plant Zn concentration correlated negatively with soil pH while ZnAC was of secondary importance. In those organogenic soils in which the reserves of native Zn were the most effectively utilized, plant Zn concentration also responded most strongly to applied Zn. In two 2-year field experiments, Zn application did not increase timothy or barley yields. Zinc concentration of timothy increased from 30 mg kg-1 to 33 and 36 mg kg-1 when 3 or 6 kg Zn ha-1 was applied, respectively. The efficiency of ZnSO4 * 7 H2O alone did not differ from that of a fertilizer where ZnSO4 * 7H20 was granulated with gypsum. Zinc concentration of barley grains increased by foliar sprays of Na2Zn-EDTA but only a marginal response to soil-applied Zn (4.8 or 5.4 kg ha-1 over three years) was detected in three 3-year experiments. High applications of Zn to soil (15 or 30 kg ha-1 as ZnSO4 * 7H2O) were required to increase Zn concentration of barley markedly. In order to prevent undue accumulation of fertilizer Zn in soil, it is proposed that Zn fertilizer recommendations for field crops should be based on both soil pH and ZnAC. In slightly acid and neutral soils, even if poor in Zn, response of plant Zn concentration to applied Zn remains small while there is a high response in strongly acid soils.Suomen viljelymaiden Zn-varojen suuruutta, liukoisuutta ja käyttökelpoisuutta kasveille tutkittiin maa-analyysein ja astiakokein. Erilaisten Zn-lannoitteiden vaikutusta raiheinän, timotein ja ohran satoon ja Zn-pitoisuuteen tutkittiin astia- ja kenttäkokein. Sinkin kokonaispitoisuus (Zntot) 106 pintamaanäytteen aineistossa oli 10 - 202 mg kg-1. Kivennäismaissa Zntot oli positiivisessa korrelaatiossa savespitoisuuden kanssa (r = 0,81***) ja eloperäisissä maissa Zntot korreloi negatiivisesti maan orgaanisen hiilen pitoisuuden kanssa (r = -0,53**). Useiden savimaiden Zntot oli yli 150 mg kg-1, kun taas muutamien runsaimmin orgaanista hiiltä sisältävien turvemaiden Zntot-varat olivat jopa alle 10mg kg-1. Vesiliukoista ja vaihtuvaa sinkkiä (Znex) uutettiin 0,5 M MgCl2-liuoksella Znox korreloi negatiivisesti maan pH:n kanssa. Pääosin orgaanisen aineksen sitomaksi oletettua sinkkiä uutettiin 0,1 M K4P2O7-liuoksella (Znpy) ja sen jälkeen samasta näytteestä 0,05 M oksalaattiliuoksella (pH 2,9) (Znox) Fe- ja Al-oksidien sitomaksi arveltua sinkkiä. Summan Znpy + Znox katsottiin kuvastavan maan sekundaaristen Zn-varojen suuruuttavastakohtana rapautumattomien mineraalien sisältämälle sinkille. Sekundaarisen sinkin määrä (mediaani 5,9 mg dm-3, n = 106) oli kaikissa maalajeissa samaa suuruusluokkaa. Sen sijaan sekundaarisen sinkin osuus (%) Zntot:sta oli pienin savimaissa (mediaani 5 %) ja suurin turvemaissa (mediaani 49 %), mikä kuvastaa maan Zntot:n määrissä olevia eroja. Maan sinkkiä uutettiin myös viljavuusanalyysissä käytettävällä happamalla ammoniumasetaatti - EDTA -liuoksella (0,5 M CH3COOH, 0,5 M CH3COONH4, 0,02 M Na2-EDTA, pH 4,65). Menetelmällä saadut tulokset (ZnAC, mediaani 2,9 mg dm-3, vaihteluväli 0,6 - 29,9 mg dm-3, n = 106) olivat kiinteässä vuorosuhteessa Znpy:n kanssa. Voidaankin arvella ZnAC:n sisältävän vesiliukoista, vaihtuvaa, orgaanisen aineksen ja Fe- ja Al-oksidien sitomaa sinkkiä. ZnAC:n pitoisuus oli muokkauskerroksessa lähes poikkeuksetta suurempi kuin jankossa. Astiakokeessa, jossa kasvatettiin neljä satoa raiheinää, ei maan Zn-varoja saatu ehdytetyiksi, vaikka raiheinän sinkinsaanti vähenikin muutamista turvemaista kokeen loppua kohti. Kasvit ottivat 2 - 68 % (mediaani 26 %, n = 107) sekundaarisen sinkin (Znpy + Znox) varoista. Suhteellisesti runsaimmin Zn-varat ehtyivät happamista, niukasti sinkkiä sisältävistä turvemaista ja muutamista karkeimmista kivennäismaista. Suhteellisesti vähiten Zn-varat ehtyivät runsaasti ZnAC sisältävistä maista sekä niukemmin ZnAC sisältävistä neutraaleista maista. ZnAC kuvasti melko hyvin raiheinän Zn ottoa, joskin menetelmä näyttää hieman yliarvioivan kasvin sinkinsaantia maista, joissa oli kesimääräistä korkeampi pH. Kivennäismaissa pH sääteli selvimmin sitä, kuinka tehokkaasti sinkkisulfaattina maahan lisätty Zn (10 mg dm-3) kohotti raiheinän Zn-pitoisuutta. Maan pH:n kohotessa Zn-lannoituksen teho heikkeni. ZnAC:n niukkuus maassa lisäsi Zn-lannoituksen tehoa. Zn-lannoitus kohotti raiheinän Zn-pitoisuutta eniten niissä eloperäisissä maissa, joiden Zn-varoilla oli taipumus ehtyä suhteellisesti voimakkaimmin. Sinkkilannoituksen vaikutusta timotein Zn-pitoisuuteen tutkittiin kahdessa kaksivuotisessa kenttäkokeessa savi- ja hietamaalla. Ilman Zn-lannoitusta kasvaneen timoitein keskimääräinen Zn-pitoisuus oli savimaalla 28 mg kg-1 ja hietamaalla 35 mg kg-1. Sinkkisulfaattina tai rakeisen kipsin ja sinkkisulfaatin seoksena kokeen alussa annettu 3 ja 6 kg Zn ha-1 lannoitus nosti timotein sinkkipitoisuutta 3 ja 7 mg kg-1. Kun näitä lannoitteita levitettiin nurmen pintaan ensimmäisen sadonkorjuuvuoden keväällä, oli vaikutus sama kuin nurmen kylvön yhteydessä maahan muokatulla lannoituksella. Nurmen pintaan levitettyjen sinkkiä sisältävien NPK-lannoitteiden Zn-lannoitusvaikutus oli vähäinen. Kolmivuotisissa kenttäkokeissa ilman Zn-lannoitusta viljellyn ohran jyvien Zn-pitoisuus oli savimaalla 29 mg kg-1, hietamaalla 18mg kg-1 ja multamaalla 39 mg kg-1. Zn-lannoitus (5,4 kg ha 1 kerralla kokeen alussa tai yhteensä 4,8 - 5,4 kg ha-1 kolmessa osassa) kohotti jyvän Zn-pitoisuutta savimaalla (pH 5,8) 5 mg kg-1, muttaa sillä ei ollut vaikutusta hietamaalla (pH 7,1) eikä multamaalla (pH 5,3), jonka jankko sisälsi runsaasti sinkkiä (ZnAC 17,2 mg dm-3). Lehti lannoitteena annettu Na2Zn-EDTA (1,8 kg Zn ha-1vuosittain) kohotti jyvän Zn-pitoisuutta kaikissa kokeissa 3-4 mg kg-1. Hietamaahan sinkkisulfaattina annettu runsaampi lannoitus (15 ja 30 kg Zn ha-1) kohotti jyvän Zn-pitoisuutta 5 tai 7 mg kg-1, mutta vaikutusta ei havaittu enää seuraavana vuonna, mikä osoittaa sinkin heikkoa käyttökelpoisuutta kyseisellä neutraalilla maalla. Sinkkilannoitus ei vaikuttanut timotein tai ohran sadon määrään. Maan pH vaikuttaa ratkaisevasti sekä luontaisen että varsinkin lannoitteena annetun sinkin käyttökelpoisuuteen. Tästä syystä maan sinkkianalyysin (ZnAC) tulkinnassa ja lannoitussuosituksia annettaessa olisi otettava huomioon myös maan pH. Neutraaleilla mailla on turha antaa Zn-lannoitusta maahan sen vähäisen vaikutuksen takia; niillä on mieluummin käytettävä lehtilannoitusta. Happamammissa oloissa myös maahan annettu lannoitus kohottaa kasvien Zn-pitoisuutta

Acid sulfate soils : A challenge for environmental sustainability

Acid sulfate (AS) soils contain sulfidic compounds formed in anaerobic conditions. In aerobic conditions, they will oxidize to sulfuric acid, which commonly lowers the pH to 3 – 4. These soils cover approximately 10,000 km2 in Finland, mainly on the western coast, and over 170,000 km2 globally. Acidity and the metals dissolved from the soil matrix and leached out of the soil are serious threats to aquatic biota. Initially, AS soils were regarded as an exclusively agricultural problem, but since the 1970s nearly all studies of AS soils have been environmentally motivated. Awareness of these soils has also risen in forestry, peat mining, and in engineering projects. Liming and water management are the key methods toward the sustainable use of these soils.Peer reviewe

Plant-availability of soil and fertilizer zinc in cultivated soils of Finland

The Zn status of cultivated soils of Finland was investigated by chemical analyses and bioassays. The effect on ryegrass of different Zn fertilizers and Zn rates was studied in pot experiments and their effect on barley and timothy in field experiments. In an uncontaminated surface soil material of 72 mineral soils and 34 organogenic soils, total Zn (Zntot) was 10.3-202 mg kg-1(median 66 mg kg-1). In mineral soils, Zntot correlated positively with clay content (r = 0.81***) and in organogenic soils negatively with organic C (r = -0.53***). Zinc bound by organic matter and sesquioxides was sequentially extracted by 0.1 M K4P2O7 (Znpy) and 0.05 M oxalate at pH 2.9 (Znox), respectively. The sum Znpy + Znox, a measure of secondary Zn potentially available to plants, was 2 - 88% of Zntot and was the lowest in clay (median 5%) and highest in peat soils (median 49%). Water-soluble and exchangeable Zn consisted of0.3 - 37% (median 3%) of Zntot, the percentage being higher in acid soils, particularly in peat soils. Zinc was also extracted by 0.5 M ammonium acetate - 0,5 M acetic acid - 0.02 M Na2-EDTA at pH 4.65 (ZnAC), the method used in soil testing in Finland. The quantities of ZnAC (median 2.9 mg dm-3, range 0.6 - 29.9 mg dm-3) averaged 50% and 75% of Znpy + Znox in mineral and organogenic soils, respectively, and correlated closely with Znpy. In soil profiles, ZnAC was with few exceptions higher in the plough layer (0 - 20 cm) than in the subsoil (30 - 100 cm). In an intensive pot experiment on 107 surface soils, four crops of ryegrass took up 2 - 68% (median 26%)of Znpy + Znox. The plant-available Zn reserves were not exhausted even though in a few peat soils the Zn supply to grass decreased over time. Variation of Zn uptake was quite accurately explained by ZnAC but increasing pH had a negative impact on Zn uptake. Application of Zn (10 mg dm-3 of soil as ZnSO4 * 7 H2O) did not give rise to yield increases. In mineral soils, increase of plant Zn concentration correlated negatively with soil pH while ZnAC was of secondary importance. In those organogenic soils in which the reserves of native Zn were the most effectively utilized, plant Zn concentration also responded most strongly to applied Zn. In two 2-year field experiments, Zn application did not increase timothy or barley yields. Zinc concentration of timothy increased from 30 mg kg-1 to 33 and 36 mg kg-1 when 3 or 6 kg Zn ha-1 was applied, respectively. The efficiency of ZnSO4 * 7 H2O alone did not differ from that of a fertilizer where ZnSO4 * 7H20 was granulated with gypsum. Zinc concentration of barley grains increased by foliar sprays of Na2Zn-EDTA but only a marginal response to soil-applied Zn (4.8 or 5.4 kg ha-1 over three years) was detected in three 3-year experiments. High applications of Zn to soil (15 or 30 kg ha-1 as ZnSO4 * 7H2O) were required to increase Zn concentration of barley markedly. In order to prevent undue accumulation of fertilizer Zn in soil, it is proposed that Zn fertilizer recommendations for field crops should be based on both soil pH and ZnAC. In slightly acid and neutral soils, even if poor in Zn, response of plant Zn concentration to applied Zn remains small while there is a high response in strongly acid soils

Phosphorus supplying capacities of soils previously fertilized with different rates of P

The residual effect of repeated P fertilizer applications was studied in a material of 30 silty clay soil samples collected from an 11-year field experiment in which a total of 0, 154, 309, 541 or 696 kg P/ha had been applied in annual doses. Half of the experiment had been limed twice with CaCO3 (10 tons/ha). In a pot experiment, six yields of Italian ryegrass were grown in soils taken from each plot, and the P uptake by the grass was determined. Soil P was extracted with water (Pw) and 0.5 M ammonium acetate-0.5 M acetic acid at pH 4.65 (PAAAC)- Reversibly adsorbed P (Pi) was extracted by a new method in which P desorbing from the soil was collected in strips of filter paper impregnated with iron hydroxide. P uptake by pot-grown grass from soils fertilized with increasing rates of P in the field corresponded to 30, 72, 100 and 112 kg larger quantities of P per hectare, compared to the soil not receiving P in the field experiment. The apparent utilization of residual fertilizer P ranged from 16 % to 25 %. The reserve of potentially desorbable P in soil had been affected much more by the fertilizer applications than had P uptake by crops in the field. The ability of the three extraction methods (Pw, Pi, PAAAC) to predict P uptake by pot-grown ryegrass was discussed. The Pi method appeared to be well suited for assessment of potentially available P reserves both in limed and unlimed soils

Effect of different rates of P fertilization on the yield and P status of the soil in two long-term field experiments

Two field experiments on P fertilization were conducted on clay soils in Southern Finland. The rates of P applied yearly in granular NPK fertilizers were 0, 13/16, 26/32, 47/56 and 60/72 kg P/ha in 1974—82/1983 —85. Oats, barley, spring wheat and winter wheat were grown, in two years also oil seed crops. In one experiment, the maximum yield of cereal grains in the first nine years (4 460 kg/ha) was reached at the P rate of 13 kg/ha, but thereafter at 32 kg P/ha. The average difference between the maximum yields and the ones obtained without P fertilization was 470 kg/ha (12 %) in 1974—80, but during the last four years the difference increased to 1 360 kg/ha (40 %), owing to the depletion of P in the plots not fertilized with P. Also in the other experiment, in which the maximum yield of cereal grains (4 790 kg/ha) was obtained at the P rate of 26/32 kg/ha, the response to P fertilization increased towards the end of the trial, the mean response during the last three years being 570 kg/ha (12 %). Phosphorus fertilization, up to the P level at which the maximum yield was reached, decreased the moisture content of cereal grains at harvest. The quantity of P extracted with 0.5 M NH4-acetate-0.5 M acetic acid (pH 4.65) decreased in the plots not fertilized with P, from 5.8 mg/l to 2.2 mg/l and from 6.2 mg/l to 1.8 mg/l in the course of the two trials. The original level of acetate-extractable P was somewhat maintained but not elevated by P rates of 26/32, 47/56 and 60/72 kg/ha. Residual P was recovered mainly in the fractions extractable with NH4F (“Al-P”) and NaOH (“Fe-P”)

Sulphate sorption by Finnish mineral soils

Sulphate sorption by 38 Finnish cultivated mineral soils was determined and its correlation with soil properties was studied. Sulphate sorption was correlated with soil pH (r =—0.46**) and with phosphate sorption (r =0.69***). With increasing soil pH, sulphate sorption decreased in relation to phosphate sorption. Phosphorus status was decisive in explaining the sulphate sorption of the soils. Even if both anions are sorbed by the same soil component (amorphous Al compounds), the sites are not available for sulphate if they are already occupied by phosphate. Sulphate sorption was negligible in soils very rich in easily soluble phosphorus. This was reflected in a close negative correlation between sulphate sorption and acid ammonium acetate (pH 4.65) extractable phosphorus (r =—0.70***). During the last few decades, phosphorus fertilization has increased the amount of easily soluble phosphorus in Finnish fields, which obviously has decreased the capacity of the soils to retain sulphate