Soil mineral N dynamics beneath mixtures of leaves from legume and fruit trees in Central Amazonian multi-strata agroforests

Long term applications of leguminous green mulch could increase mineralizable nitrogen (N) beneath cupuaçu trees produced on the infertile acidic Ultisols and Oxisols of the Amazon Basin. However, low quality standing cupuaçu litter could interfere with green mulch N release and soil N mineralization. This study compared mineral N, total N, and microbial biomass N beneath cupuaçu trees grown in two different agroforestry systems, north of Manaus, Brazil, following seven years of different green mulch application rates. To test for net interactions between green mulch and cupuaçu litter, dried gliricidia and inga leaves were mixed with senescent cupuaçu leaves, surface applied to an Oxisol soil, and incubated in a greenhouse for 162 days. Leaf decomposition, N release and soil N mineralization were periodically measured in the mixed species litter treatments and compared to single species applications. The effect of legume biomass and cupuaçu litter on soil mineral N was additive implying that recommendations for green mulch applications to cupuaçu trees can be based on N dynamics of individual green mulch species. Results demonstrated that residue quality, not quantity, was the dominant factor affecting the rate of N release from leaves and soil N mineralization in a controlled environment. In the field, complex N cycling and other factors, including soil fauna, roots, and microclimatic effects, had a stronger influence on available soil N than residue quality.

Soil CO2 efflux in central Amazonia: environmental and methodological effects

Soil respiration plays a significant role in the carbon cycle of Amazonian rainforests. Measurements of soil respiration have only been carried out in few places in the Amazon. This study investigated the effects of the method of ring insertion in the soil as well as of rainfall and spatial distribution on CO2 emission in the central Amazon region. The ring insertion effect increased the soil emission about 13-20% for sandy and loamy soils during the firsts 4-7 hours, respectively. After rainfall events below 2 mm, the soil respiration did not change, but for rainfall greater than 3 mm, after 2 hours there was a decrease in soil temperature and respiration of about 10-34% for the loamy and sand soils, with emissions returning to normal after around 15-18 hours. The size of the measurement areas and the spatial distribution of soil respiration were better estimated using the Shuttle Radar Topographic Mission (SRTM) data. The Campina reserve is a mosaic of bare soil, stunted heath forest-SHF and tall heath forest-THF. The estimated total average CO2 emissions from the area was 3.08±0.8 µmol CO2 m-2 s-1. The Cuieiras reserve is another mosaic of plateau, slope, Campinarana and riparian forests and the total average emission from the area was 3.82±0.76 µmol CO2 m-2 s-1. We also found that the main control factor of the soil respiration was soil temperature, with 90% explained by regression analysis. Automated soil respiration datasets are a good tool to improve the technique and increase the reliability of measurements to allow a better understanding of all possible factors driven by soil respiration processes.

Estudos químico-agrícolas sôbre o enxofre

1. Analyses of soluble sulphates in 2 N ammonium chloride extracts of 24 samples of soils of the state of São Paulo, Brazil, S. A., showed a sulphur content varying from 0,0013 g per 100 g (found in the b layer of a genuine "terra roxa") to 0,007 g per 100 g of soil (b layer of a soil of depression without definite characteristics). (The results are expressed as elemental sulphur). Determinations of total sulphur in 56 samples of soils of the same state using the method of fusion with sodium carbonate and sodium nitrate revealed 0.007 g of elemental S per 100 g of soil as the lowest value (found in several soil types) and 0.096 g as the highest one (found in the b layer of an ar-quean soil). Apparently soluble sulphates accumulate in the upper layers and total sulphur does the opposite. It was found a strong correlation between total S and carbon content. 2. Under laboratory conditions, in a compost of fresh soil, powdered sulphur and apatite, it was verified after a three months period of incubation that the pH value lowered from 6.30 to 3.23; the citric acid solubility of apatite increased to 271.1 per cent of the original one. Lupinus sp. grown in soil manured with sulphur and apatite has showed fresh and dry weights higher than the plants in control pots; the results are significant at 5% level of probability; phosphorus content is also higher in the manured plants. It was observed a net influence of the apatite plus sulphur treatment on the weight of root nodosities that was four times greater than in the control plants. 3. Nearly five hundred determinations of S, N and P were carried out in 35 species of plants cultivated in the state of São Paulo. A great variation in the amounts of these elements was observed. As a general rule, the leaves contain more sulphur than the stems and roots show the lowest percentages. The conjunct roots and stem of guar (Cyamopsis psoraloides) revealed only 0.019 per cent sulphur; the leaves of kale showed the highest sulphur content, i. e., 2.114%. Apparently there is no correlation between the amounts of S, N and P. The ratio S/N increases from 0.006 (guar) to 0.485 (kale). The ratio S/P, always higher than the corresponding S/N, increases from 0.082 (guar) to 6.381 (older leaves of tomato plants). It is interesting to mention that several among the most important crops in the state of São Paulo namely, cotton, rice, coffee and sugar cane contain more sulphur than phosphorus. 4. Tomato plants cultivated in nutrient solution lacking sulphur showed the following visual symptons of deficiency : chlorosis first in the younger leaves and afterwards in all the leaves; anthocyanin pigments in the petioles and stems; absence of fruits; primary roots stunted and secondary ones longer than in the control plants; stems slender, hard, woody. The histological study of petioles suffering from sulphur deficiency revealed anthocyanin in the parenchyme layer instead of clo-rophyll pigments observed in normal petioles; in the chlorotic leaves the large chloroplasts present only the stroma but the small ones have a little amount of green pigments. Chemical analysis revealed in the abnormal plants : less sulphur and an increased proportion of phosphorus; older leaves contain more sulphur and less phosphorus than the younger ones probably due to physiological difficulties in translocation of sulphur bearing material; increased amount of total N attributed to accumulation of nitrates; marked decrease in ash, sugars and starch; increased proportion of crude fiber and dry material. In the plants suffering from sulphur deficiency photosyntetic rate decreased 34 per cent. 5. Tomato plants were succesfully cultivated in nutrient solution in absence of mineral sulphur but in presence of cysteine. The plants absorbed sulphur, under that form and were able to grow up quite well; the fruiting was normal. In this way rested cleary demonstrated the possibility of absorption of organic sulphur without previous mineralization and its utilization in the building up of protein molecules.

Tracer studies in the coffee plant (Coffea arabica L.)

Due to the great importance of coffee to the Brazilian economy, a good deal of the work carried out in the "Laboratório de Isótopos", E. E. A. "Luiz de Queiroz", Piracicaba, S. Paulo, Brazil, was dedicated to the study of some problems involving that plant. The first one was designed to verify a few aspects of the control of zinc deficiency which is common in many types of soils in Brazil. An experiment conducted in nutrient solution showed that the leaf absorption of the radiozinc was eight times as high as the root uptake; the lower surface of the leaves is particularly suited for this kind of absorption. Among the heavy metal micronutrients, only iron did not affect the absorption of the radiozinc; manganese, copper, and molybdenum brought about a decrease of fifty per cent in total uptake. In another pot experiment in which two soils typical of the coffee growing regions were used, namely, a sandy soil called "arenito de Bauru" and a heavy one, "terra roxa", only O.l and 0.2 per cent of the activity supplied to the roots was recovered", respectively. This indicates that under field conditions the farmer should not attempt to correct zinc deficiency by applying zinc salts to the soil: leaf sprays should be used wherever necessary. In order to find out the most suitable way to supply phosphatic fertilizers to the coffee plant, under normal farm conditions, an experiment with tagged superphosphate was carried out with the following methods of distribution of this material: (1) topdressed in a circular area around the trees; (2) placed in the bottom of a 15 cm deep furrow made around the plant; (3) placed in a semicircular furrow, as in the previous treatment; (4) sprayed directly to the leaves. It was verified that in the first case, circa 10 per cent of the phosphorus in the leaves came from the superphosphate; for the other treatments, the results ware, respectively: 2.4, 1.7, and 38.0 per cent. It is interesting to mention that the first and the last methods of distribution were those less used by the farmers; now they are being introduced in many coffee plantations. In a previous trial it was demonstrated that urea sprays were an adequate way to correct nitrogen deficiency under field conditions. An experiment was then set up in which urea-C14 was used to study the metabolism of this fertilizer in coffee leaves. In was verified that in a 9 hours period circa 95 per cent of the urea supplied to the leaves had been absorbed. The distribution of the nitrogen of the urea was followed by standard chemical procedures. On the other hand the fate of the carbonic moiety was studied with the aid of the radiochromatographic technique. Thus, the incorporation of C14 in aminoacids, sugars and organic acids was ascertained. Data obtained in this work gave a definite support to the idea that in coffee leaves, as in a few other higher plants, a mechanism similar to the urea cycle of animals does exist.

Estudos sôbre a alimentação mineral do cafeeiro. II: absorção do superfosfato radioativo pelo cafeeiro (Coffea arabica L., var. Bourbon Amarelo) em condições de campo

In order to find out the best way to supply phosphorus to coffee plants when growing in "terra roxa misturada", a red soil with a high fixing capacity, tagged superphosphate was applied by the following procedures: (1) topdressed in a circular strip around the trees; (2) placed in the bottom of a circular furrow 15 cm deep; (3) placed in a semicircular furrow also 15 cm deep; (4) sprayed directly to the leaves. In each case 150 gms. of ordinary superphosphate tagged with H3 P32 O4 to give 5 X 10(9) c.p.m. were given to the two and half year old coffee plants. It was found that for the several treatments of the total phosphorus in the leaves the following values, on a per cent basis, came from the applied superphosphates: (1) topdressed 10.2 per cent, (2) circular furrow 2.4 per cent, (3) semicircular furrow 1.7 per cent, (4) sprayed 38.0 per cent; one can see, then, that methods (2) and (3) commonly used by the coffee planters are a very inefficient way to supply phosphorus in this type of soil. The remarkable foliar absorption was checked twice: a water culture experiment was carried out, the radiophosphorus being supplied by brushing it in the upper and lower surfaces of a given leaf; radioactivity was detected all over the plant as a result both of absorption and translocation; on the other hand, leaves collected from the sprayed trees were radioautographed; the radioautographs showed the pattern of distribution of the P32 which indicates true absorption rather than a surface contamination. In another locality, an experiment was caried out with 8 year old plants growing in "arenito de Bauru" which is a sandy soil with much less phosphorus fixing capacity. In this experiment the aim was to compare absorption of tagged superphosphate by trees growin under mulch against plants not receiving this treatment, The uptake of phosphorus was the same for both sets of plants. In both field experiments soil samples down to 15 cm in the profile were collected and its 0.2NHC1 soluble phosphorus was counted; rather significant values were observed mainly in the upper 5 cm layers.

Contribuição ao estudo da aplicação do método da diagnose foliar ao algodoeiro (Grossypium hirsutum L., var. I. A. C. 817) II

This paper deal with one experiment carried out in order to study the correlation between petioles analysis and seed cotton yield. A 3X3X3 factorial with respect to N, P2 0(5) and K2 O was installed in a sandy soil with low potash content and medium amounts of total N and easily extractable P. Two kinds of petioles, newly mature were collected for analysis: those attached to fruit hearing branches, and petioles located on the stem; the first group is conventionally named "productive petioles"; The second one is called "not productive petioles". Petioles' sampling was done when the first blossoms appeared. Yield date showed a marked response to potash, both nitrogen and phosphorus having no effect. Very good correlation was found between petioles potash and yield. Both types of petioles samples were equally good indicators of the potash status of the plants. By mathematical treatment of the date it followes that the highed yield which was possible under experimental conditions, 1.562 kg of seed cotton per hectare would be reacher by using 128 kg of K2O per hectare. With this amount of potash supplied to the plants the following K levels would be expected in the petioles: "productive petioles" "not productive petioles" 1,93 % K 1,85 % K

A absorção de nitrogênio, fósforo, potássio, cálcio, magnésio, enxôfre e silício pela cana de açúcar, Co 419, e o seu crescimento em função da idade

This paper describes the data obtained for the growth of sugar cane, Variety Co 419, and the amount and rate of absorption of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and silicon, according to the age of the plant, in the soil and climate conditions of the state of S. Paulo, Brazil. An experiment was installed in the Estação Experimental de Cana de Açúcar "Dr. José Vizioli", at Piracicaba, state of S. Paulo, Brazil, and the soil "tèrra-roxa misturada" presented the following composition: Sand (more than 0,2 mm)........................................................................ 8.40 % Fine sand (from 0,2 to less than 0,02 mm)................................................. 24.90 % Silt (from 0,02 to less than 0,002 mm)...................................................... 16.40 % Clay (form 0,002 mm and less)................................................................ 50.20 % pH 10 g of soil and 25 ml of distilled water)..................................................... 5.20 %C (g of carbon per 100 g of soil)................................................................. 1.00 %N (g of nitrogen per 100 g of soil)............................................................... 0.15 P0(4)-³ (me. per 100 g of soil, soluble in 0,05 normal H2SO4) ............................... 0.06 K+ (exchangeable, me. per 100 g of soil)....... 0.18 Ca+² (exchangeable, me. per 100 g of soil)...... 2.00 Mg+² (exchangeable, me. per 100 g of soil)...... 0.66 The monthly rainfall and mean temperature from January 1956 to August 1957 are presented in Table 1, in Portuguese. The experiment consisted of 3 replications of the treatments: without fertilizer and with fertilizer (40 Kg of N, from ammonium sulfate; 100 Kg of P(2)0(5) from superphosphate and 40 Kg K2 O, from potassium chloride). Four complete stools (stalks and leaves) were harvested from each treatment, and the plants separated in stalks and leaves, weighed, dried and analysed every month from 6 up to 15 months of age. The data obtained for fresh and dry matter production are presented in table 2, and in figure land 2, in Portuguese. The curves for fresh and dry matter production showed that fertilized and no fertilized sugar cane with 6 months of age presents only 5% of its total weight at 15 months of age. The most intense period of growth in this experiment is located, between 8 and 12 months of age, that is between December 1956 and April 1957. The dry matter production of sugar cane with 8 and 12 months of age was, respectively, 12,5% and 87,5% of the total weight at 15 months of age. The growth of sugar cane in relation to its age follows a sigmoid curve, according to the figures 1, 2 and 3. The increase of dry matter production promoted by using fertilizer was 62,5% when sugar cane was 15 months of age. The concentration of the elements (tables 4 and 5 in Portuguese) present a general trend of decreasing as the cane grows older. In the stalks this is true for all elements studied in this experiment. But in the leaves, somme elements, like sulfur and silicon, appears to increase with the increasing of age. Others, like calcium and magnesium do not show large variations, and finally a third group, formed by nitrogen, phosphorus and potassium seems to decrease at the beginning and later presents a light increasing. The concentration of the elements was higher in the leaves than in the stalks from 6 up to 15 months of age. There were some exceptions. Potassium, magnesium and sulfur were higher in the stalks than in the leaves from 6 up to 8 or 9 months of age. After 9 months, the leaves presented more potassium, magnesium and sulfur than the stalks. The percentage of nitrogen in the leaves was lower in the plants that received fertilizer than in the plants without fertilizer with 6, 7, 8, 10, 11 and 13 months of age. This can be explained by "dilution effect". The uptake of elements by 4 stools (stalks and leaves) of sugar cane according to the plant age is showed in table 6, in Portuguese. The absorption of all studied elements, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur and silicon, was higher in plants that received fertilizer. The trend of uptake of nitrogen and potassium is similar to the trend of production of dry matter, that is, the maximum absorption of those two nutrients occurs between 9 and 13 months of age. Finaly, the maxima amounts of elements absorbed by 4 stools (stalks and leaves) of sugar cane plants that received fertilizer are condensed in the following table: Element Maximum absorption in grams Age of the plants in months Nitrogen (N) 81.0 14 Phosphorus (P) 6.8 15 Potassium (K) 81.5 15 Calcium (Ca) 19.2 15 Magnesium (Mg) 13.9 13 Sulfur (S) 9.3 15 Silicon (Si) 61.8 15 It is very interesting to note the low absorption of phosphorus even with 100 kg of P2O5 per hectare, aplied as superphosphate. The uptake of phosphorus was lower than calcium, magnesium and sulfur. Also, it is noteworthy the large amount of silicon absorbed by sugar cane.

A composição química da goiabeira (Psidium guajava L.)

This paper deals with the mineral composition fresh and dry matter production of different organs of 4, 5 old guava (Psidium guajava L.) growth on sandy soil (Savanna) without fertilizer. The data obtained for fresh and dry matter productior are present in table 2 (in Portuguese). The concentration of the elements are presented in table 3 (in Portuguese). Finally, the total amounts of elements absorbed by guava are given in the following table: Element Plant (grams) Fruits (grams) Nitrogen (N) 42,55 20,4 Phosphorus (P) 3,84 2,3 Potassium (K) 52,01 31,3 Calcium (Ca) 47,81 0,2 Magnesium (Mg) — 2,4

A disponibilidade do fósforo de oiversos fosfatos estudada por meio do método de Neubauer"

In order to study the phosphorus availability from various phosphates fertilizers an experiment was performed according to the biological seedling method of Neubauer. The physico-chemical properties of the soil "terra roxa-misturada", a red soil derived from basaltic rocks are given in the Portuguese text. Rice (Oryza sativa, L.) instead of rye (Secale cereale, L.) was used. Five replications of each of the following treatments were made: 1 - check, with 350 g of sand 2 - 350 g of sand plus 100 g of soil 3 - 350 g of sand and plus 100 g of soil plus 40 mg of P2O5, from superphosphate. 4 - 350 g of sand plus 100 g of soil plus 40 mg of P2O5. from Olinda (Brazil) phosphorite. 5 - 350 g of sand plus 100 g of soil plus 40 mg of P2O5 from Florida (U. S. A.) phosphorite. 6 - 350 g os sand plus 100 g of soil plus 40 mg of P2O5 from Hyperphosphate, a commertial name of a North African (Gafsa) phosphorite. 7 - 350 g of sand plus 100 g of soil plus 40 mg of P2O5 from Araxá (Brazil) apatite. After 18 days of growth, the roots and tops of rice seedlings were harvested and analysed for phosphorus, and the results are summarized in table 1. Table 1 - Milligrams of P2O5 determined in rice seedlings. Treatments Mean of 5 replications mg of P2O5 1 ..................... 24.196 2 ..................... 23.850 3 ..................... 30.724 4 ..................... 27.620 5 ..................... 27.480 6..................... 30.210 7 ..................... 26.032 The least significant difference at the 5% level by Tukey's procedure for comparisons among the treatments means is 1.365 mg of P(2)0. It is interesting to observe that rice plants did not take any phosphorus from the soil according to he data of the treatments n.° 1 and n.° 2. This can be explained by the high phosphorus fixing capacity of the soil "terra roxa misturada".

Estudo sobre a Alimentação Mineral do algodoeiro I: marcha da absorpção do macronutrientes (Nota prévia)

Cotton (variety I. A. C. 11) was grown on a sandy soil under two treatments, namely: (1) NPK + lime and (2) no fertilizers. Three weeks after planting a systematic sampling of entire plants was done every other week. In the laboratory determinations of dry weight were made and afterwards the various plant partes were submitted to chemical analyses, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) being determined. The aim of this work was to obtain information on the periods in which the absorption of the several macronutrients was more intense, this providing a clue for time of application of certain mineral fertilizers. Data obtained hereby allowed for the following main conclusions. The initial rate of growth of the cotton plant, judged by the determinations of dry weight, is rather slow. Seven weeks after planting and again five weeks two distinct periods of rapid growth take place. The uptake of macronutrients is rather small until the first flowers show up. From there on the absorption of minerals is intensified. From the time in which fruits are being formed to full maturity, the crop draws from the soil nearly 75 percent of the total amount of elements required to complet life cycle. This seams to point out the need for late dressings of fertilizers, particularly of those containing N and K. The following amounts of element in Kg/ha were absorbed by the fertilized plants: N - 83.2 P - 8.1 K - 65.5 Ca - 61.7 Mg - 12.8 and S - 33.2. The three major macronutrients, namely, N. P and K are exported as seed cotton in the following proportions with respect to the total amounts taken up by the entire crop: N - 1/3, P - 1/2 and K - 1/3.

Sulfur fractions and carbon-nitrogen-phosphorus-sulfur relationships in some Brazilian and Iowa soils

O atual conhecimento relativo à distribuição em percentagem das várias frações de enxofre nos solos provem principalmente dos estudos dos solos de regiões temperadas. Em vista disso, este estudo foi conduzido para determinar as frações do S e as relações C-N-P-S em alguns solos da região subtropical dos Estados de São Paulo e do Paraná, Brasil, e comparar estes valores nestes solos com aqueles nos solos do Estado de Iowa, dos Estados Unidos da América do Norte. As análises das frações de enxofre nos solos dos dois países, indicaram que os solos do Brasil contem sulfato inorgânico adsorvido. Expressos como percentagem do S total, os solos do Brasil acusaram de 5 a 23% (média 11%) de S-sulfato inorgânico, de 20 a 65% (média 40%) de S-ester sulfato, de 5 a 12% (média 7%) de S-ligado ao Carbono e de 24 a 59% (média 42%) de S orgânico não identificado. As percentagens correspondentes nos solos de Iowa foram de 2 a 8% (média 5%) de S-sulfato inorgânico, de 43 a 60% (média 50%) de S-ester sufato, de 7 a 18% (média 11%) de enxofre ligado ao carbono e de 30 a 39% (média 34%) de S orgânico, não identificado. Outrossim, não foi encontrado o enxofre inorgânico não-sulfato em nenhum dos solos analisados. Houve grandes variações nas relações C, N, Ρ e S entre solos brasileiros quando comparados com aqueles do Iowa.

Studies on the mineral nutrition and fertilization of the passion fruit plant (Passiflora edulis f. flavicarpa): II - placement of fertilizer phosphorus

A localização do superfosfato (marcado com P32) no maracujá em produção foi estudada em condições de plantação comercial. Verificou-se que as aplicações em sulcos circulares ou faixas superficiais ao redor da planta tem eficiência equivalente sendo esses métodos três vezes superiores à localização do adubo em furos no solo. A pulverização foliar, por sua vez, mostrou-se 20 vezes mais eficiente que a aplicação no solo de acordo com os dois primeiros métodos.

Studies on the mineral nutrition and fertilization of the passion fruit plant (Passiflora edulis F. flavicarpa): II. placement of fertilizer phosphorus

1. Tagged superphosphate was applied to 2.5 year old passion fruit plants from a commercial plantation established in a sandy loam. 2. 100 grams of the fertilizer were distributed in the following ways: in a circular furrow 20 cm around the plant 40 cm from the stems; in a circular strip 10 cm wide, 40 cm from the stems; in six holes around the plants, 40 cm from the stems 20 cm deep, 2.5 cm in diameter. 3. 10 grams of the fertilizer in 11 of water were sprayed to the leaves. 4. Three weeks after the treatments were made, leaf samples were taken for analysis. 5. Determinations of specific activities both in the leaves and in the fertilizer used have shown that R in the plant was derived from the superphosphate in the following relative proportions (by making the first treatment equal to 100): circular furrow = 100; circular strip = 120; holes = 30; foliar spray = 230.