Resumo em Inglês:

An experiment was started in 1931 for the purpose of making a comparative study of the productivity of following varieties of Coffea arabica L, : Nacional (Coffea arabica L. var. typica Cramer) Amarelo de Botucatu (Coffea arabica L. var. typica Cramer forma xanthocarpa (Caminhoá) Krug) Bourbon (Coffea arabica L. var. bourbon (B. Rodr.) Choussy) Bourbon amarelo (Coffea arabica L. var. bourbon (B. Rodr.) Choussy forma xanthocarpa Krug) Sumatra (Coffea arabica L. var. typica Cramer) Maragogipe (Coffea arabica L. var. maragogipe Hort. ex Froehner) The results obtained from this experiment for the period 1935-1938 have been the subject of a previous publication. The present paper concerns results obtained from the same experiment for the period 1939-1946. The data obtained have been analysed by varieties and years in relation to : date of ripening of coffee berries, average size of coffee beans and total production. The results of this analysis showed that there were definite annual variations in production by varieties. With respect to ripening of fruits (cherries) on the varieties tested, it was found that the Amarelo de Botucatu variety had the earliest date of ripening in every year. The Nacional and Sumatra varieties varied by years but they were always later than the Amarelo de Botucatu in date of maturity of the cherries. The fruits of Bourbon and Boubon Amarelo were slightly later than all of of the above mentioned varieties and the Maragogipe matured fruit later than all other varieties studied. The data on the average size of coffee beans showed that the Maragogipe variety produced the largest bean. The Bourbon Amarelo and Bourbon produced beans of the smallest size. The Nacional, Sumatra and Amarelo de Botucatu produced beans that were intermediate in size between the Maragogipe and Bourbon. The analysis of production showed that for each year for the first four years (1935-1938) there was a definite yearly increase in production for each variety tested. The data obtained for subsequent years (1939-1946) show that, for all except the Maragogipe variety, each year with a high yield was followed by a year with lower coffee production (see figure 1). On the basis of the total production for the entire period studied (1935-1946) it was found that Bourbon Amarelo variety was the most productive followed closely by the variety Bourbon. The Sumatra variety was intermediate in total production and appreciably less than the Bourbon types. The lowest yielding varieties in this experiment were Nacional, Amarelo de Botucatu and Maragogipe. The production data have also been studied by four year periods and as a result certain interesting minor variations in relation to varieties have been noted. A more detailed statistical analysis of the production data from this experiment has been carried out by Prof. W. L. Stevens (see following article in this issue). He has showed that the coffee varieties studied can be placed in three statistically different classes. The varieties, by classes, according to their decreasing capacity of production, are as follows : a ) Bourbon Amarelo and Bourbon ; b) Sumatra ; c) Nacional, Amarelo de Botucatu and Maragogipe.

Resumo em Inglês:

This paper describes the statistical analysis of a varietal trial with two unusual characteristics : (i) The plant (coffee) is one of those which show strong maxima and minima of production in alternate years. This phenomenon must be prevented from masking or biasing the other varietal comparisons in which we are interested. (ii) The design of the experiment is systematic. It was laid down in Campinas, Brazil, in 1933 at a time when the principles of randomisation were not so widely known as they are today. THE EXPERIMENT AND DATA. Six varieties are compared, denoted by A B C D E and F (see page 104). They are planted in thirty rows, each with 50 plants, according to the systematic design : A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F Data for twelve years are available in quadro 1 but those of the small and irregular yields in the first two years were discarded. The mean yields of the remaining ten years (1935-1946) appear by figure 1 to be fairly regular and consistent in their behaviour. Most of the plants, but by no means all, showed their maxima in the even years. STATISTICAL ANALYSIS. The quantity of primary interest is the mean yield over the whole period. It is essential that these means should be based (as here) on an even number of years in order to eliminate, from their comparisons, the effect of the alternations of maxima and minima. The magnitude of the oscillation is conveniently measured by total of even years minus total of odd years. Finally we need a linear function of the annual yields for measuring secular trend in order to discriminate varieties which are slowly gaining on the others. The usual linear orthogonal polynomial (with coefficients -9, -7, -5, etc.) is unsuitable because it is not independent of the component of oscillation. A suitable function is obtained instead by using the coefficients -2 -2 -1 -1 0 0 +1 +1 +2 +2. The coefficients of the three linear functions thus defined are set out in quadro 2 (page 107), where it will be verified that they are mutually orthogonal. The effect of the heterogeneity of the soil is as far as possible eliminated (separately for the three functions) by an analysis of covariance, using the number of the row (1-30) as the concommitant observation. A simple linear regression formula is however inadequate. The regressions were taken to the fifth degree by means of orthogonal polynomials. Since the "between varieties" contribution must be removed from the sums of squares and products, the regression coefficients are no longer independently obtainable. It is found however that the normal equations fall into two sets, one yielding the regression coefficients of odd degree and the other those of even degree. Consequently the use of orthogonal polinomiais still effects a considerable saving of work. The computations are set out in full in quadro 3 and in abbreviated form in quadro 4 and 5 for the total, the oscillation and the trend respectively. (Note that the comma indicates the decimal point.) We find that a quadratic regression is adequate for the first and cubic regressions for the others. For the sake of uniformity, a cubic regression was used in every case. The residuals found by subtracting the varietal means from the rows are plotted in figures 2a, 3 and 4a. respectively, together with the regression curves and the 2.5% control limits. These control charts suggest that it is not unreasonable to suppose that the remaining variation is random. Next we use the regression formulae to correct the varietal means. The approximate 80% fiducial intervals of the mean annual yields (kg per row) and the rate of increase of yield (kg per row per year per year) are shown in figures 2b and 4b respectively. In the case of the component of oscillation, the analysis of covariance failed to show the slightest suggestion of differences between varieties. DISCUSSION. An examination of the regressions on number of row reveals the interesting fact that the more fertile portions of the field produce lower yields in the odd years than the less fertile portions. The reason is presumably that the heavier yields in the even years, by exhausting the plant, depress the yields in the following years. The major differences between varietal means over the ten years were sufficiently clear even before the analysis though some of the adjustments are appreciable. A striking fact is that, although there are big general differences between varieties, there are no significant differences between them in respect of the amplitude of oscillation. In other words, the increment of yield in the better varieties is obtained equally in odd and even years. In spite of the large component of oscillation, it is possible to discriminate varieties in respect of their rate of increase of yield (figure 4b). CONCLUSIONS. (i) The extra difficulty introduced by the strong alternations of yield from year to year can be solved b y the choice of suitable orthogonal functions of yearly yields. (ii) Once again a systematic design is found wanting - it fails to eliminate the effect of soil heterogeneity from varietal comparisons. This defect can however be removed, for practical purposes, by an adequate analysis of covariance on row number.

Resumo em Inglês:

The empovrishment of the soil brought about by erosion and cultivation of cotton has been studied in experimental plots where catch tanks were employed to collect soil removed by erosion. These tests have been carried out by the Soil Conservation Department at the Experiment Station of the Instituto Agronômico of Campinas, in Pindorama, and on the "Arenito Bauru" soil type representative of the region. Actually sixty percent of all coffee and eighty percent of all cotton cultivation in the State of São Paulo is on the "Arenito Bauru" soil type. Thus the data collected, although preliminary, are of great interest, and indicate that the empovrishment of the "Arenito Bauru" soil by erosion is extremely rapid. It is also pointed out that the "Arenito Bauru" soils are the most highly erodable of all soil types in the State of São Paulo. A chemical analysis was made of representative samples of the original soils in the experimental plots and of samples of soil carried in the runoff, for the purpose of determining the losses due to erosion. It has been determined that the soil transported in the runoff is proportionally very much richer in mineral elements than was the original soil. The data obtained from analysis of samples showed that soil eroded from the experimental plots contained 2.0 times as much organic material, 2.8 times as much P2O5 ; 2.3 times as much K2O, and 1.9 times as much CaO, as was determined present in the samples obtained from the original soil of the experimental plots. In the runoff water it has determined that calcium was present in larger quantities than other elements. On the basis of data obtained from the experimental plots with cotton cultivation, an evaluation and comparison was made of the amount of mineral elements lost by erosion and the amount used by the cotton crop. It was found that the empovrishment of the soil by loss of organic material and chemical elements was due more to erosion than to utilization of these in the production of harvested cotton. A discussion is given of forms of organic and mineral fertilizers to be employed on "Arenito Bauru" soils, taking into consideration the physical and chemical nature of these soils.

Resumo em Português:

O autor descreve, neste trabalho, investigações realizadas sôbre as caraterísticas de cobertura e fixação do solo, de dez espécies vegetais. A técnica e o método que empregou consistiram, em síntese, em fazer cortes da parte aérea e em escavar blocos de terra com raízes a determinadas alturas e profundidades, numa área de 0,25 m², de forma a obter a densidade de cobertura do solo pela parte aérea e de travamento pela parte subterrânea, a diferentes distâncias da superfície do solo. Os resultados obtidos levaram às seguintes conclusões preliminares : a) A espécie Paspalum notatum Flügge, compreendendo duas variedades - grama Batatais de fôlha larga e grama Americana de folha estreita, apresentou a maior percentagem em pêso e volume da parte aérea e subterrânea a 2 e 8 centímetros, acima e abaixo do nível do solo. b) A grama das Roças (Paspalum dilatatum Poir.) oferece boa cobertura, mas o efeito de travamento é fraco para tôdas as profundidades, c) O capim Kikuiu (Pennisetum clandestinum Chio v.), a grama Tio Pedro (Paspalum convexum H. B.) e o capim Gengibre (Paspalum maritimum Trin.) proporcionam boa cobertura e sofrível travamento do solo. d) A grama Sêda (Cynodon dactylon Pers.) e a grama Portuguêsa (Panicum repens L.) deram dados satisfatórios para tôdas as alturas e profundidades, e) A Margaridinha (Wedelia paludosa L.) possibilita ótima cobertura e bom travamento a tôdas as profundidades, f) O Kudzu comum (Pueraria thumbergiana Benth.) forneceu dados bem elevados, mesmo para o último bloco subterrâneo, que atinge 80 centímetros de profundidade. Em face dos dados obtidos, o autor faz considerações sôbre a utilização das vegetações estudadas em práticas conservacionistas de caráter vegetativo

Resumo em Inglês:

This paper describes the investigations carried out and the methods employed to determine the characteristics of ten plant species for use in various aspects of soil erosion control. Seed of the ten plant species to be studied were sowed in beds. After a suitable period of time for growth of the plants, sample areas 0.25 sq. mt. were selected. The number of plants and total volume and weight of the plant growth at specific levels (0-2 cm, 2-8 cm, 8-26 cm, 26-80 cm) both above and below ground were measured. The results obtained have led to the following preliminary conclusions. Of the plants studied the species Paspalum notalum Flügge, composed of two varieties, large leafed Batatais and Bahia grass, were found to have the largest volume and weight of plant growth in the area 2 to 8 centimeters above and below the soil surface. Roças grass (Paspalum dilatatum Poir) proved to be a good ground cover but root penetration and development was relatively poor at all depths. The Kikuiu grass (Pennisetum clandes-tinum Chiov.), Tio Pedro grass (Paspalum convexum H. B.) and Gengibre grass (Paspalum maritinum Trin.) produced a good ground cover but root development in the soil was only fair. The Bermuda grass (Cynodon dactylon Pers.) and Portuguêsa grass (Panicum repens L.) gave measurements of volume and weight of plant growth at all levels both above and below ground which indicated that these plants would be relatively satisfactory in erosion control work. The data obtained from the study of Margaridinha (Wedelia paludosa L.) indicated this species is very good both from standpoint of a cover crop and in its capacity to hold the soil in place. The common Kudzu (Pueraria thumbergiana Benth.) gave measurements of top and root development that show that it is a very good species. The author discusses in a general way all of the above mentioned species in relation to specific uses in soil conservation.

Resumo em Português:

No estado de São Paulo a erosão é ocasionada, em grande parte, pelas águas das chuvas. Estas, desagregando o solo, arrastam sua parte mais útil, levando quantidades consideráveis de sais minerais e de matéria orgânica. Daí o grande interesse de se avaliar, por meio de sistema coletores, as perdas pela erosão, a fim de se determinar quais as práticas conservacionistas mais eficientes nos vários tipos de solo e modalidades de cultivo. Em São Paulo, o primeiro dêsses sistemas coletores foi instalado, pela Secção de Conservação do Solo, em 1944, na Estação Experimental de Pindorama, seguindo-se, logo depois, a instalação de outros em Campinas, Mococa e Ribeirão Prêto. O objeto do presente trabalho é o de apresentar os vários métodos para medição de enxurrada. Fêz-se especial referência ao método de coleta de uma fração alíquota, empregado para determinar as perdas pela erosão, nos talhões experimentais da Estação Experimental de Ribeirão Prêto, situada em zona de solo do tipo terra roxa legítima. Foi feita uma descrição minuciosa deste método e do sistema coletor empregado. Para ilustrar seu funcionamento, foram tomados os dados relativos às perdas ocorridas, em um dia de chuva, num sistema coletor instalado em um talhão para estudo de práticas conservacionistas em cafèzal. Foi, a seguir, apresentada a marcha dos cálculos para determinação do volume de enxurrada, da quantidade de terra na enxurrada e do fator de conversão de volume para pêso de terra arrastada. Baseando-se nas determinações feitas durante o ano agrícola de 1947/48, verificou-se que, para a terra roxa legítima, o valor médio do teor de terra na enxurrada é de 0,2344% e o fator de conversão de volume para peso de terra arrastada é de 1,0821. Por êsses valores, calculou-se que o total de terra arrastada, no dia tomado para exemplificação do método, foi de 62,921 kg por 1000 m², e para uma precipitação pluviométrica de 88,4 mm.

Resumo em Inglês:

The purpose of this paper is to present detailed information that may be helpful to others undertaking soil erosion and runoff studies. A general decription is given of the methods used for determining soil erosion and water losses from experimental plots. A detailed description is presented of the method for colleting a fraction of the total runoff, using slot divisors of the Geib type. An example is given with calculations showing soil erosion losses, occuring in one single day, from an experimental plot located in Ribeirão Prêto, on purple soil, (terra roxa legítima) and bearing coffee trees on a slope of 6.5%. The average values of soil density in runoff and the conversion factor from volume to weight of soil are also given so that determination of the weight of soil lost from the coffee experimental plot, could be made.