Julio Cesar Barreneche Lhamby

Fifty years of wheat breeding in Southern Brazil: yield improvement and associated changes

The objective of this study was to assess the impact of genetic breeding on grain yield, and to identify the physiological traits associated to the increment in yield and their related growth processes, for wheat cultivars grown in Southern Brazil, in the past five decades. Seven wheat cultivars released between 1940 and 1992, were compared for physiological aspects associated with grain yield. Grain yield, biological yield, biomass partitioning, harvest index and grain yield components were also determined. The number of grains per square meter was more affected by plant breeding and was better correlated with grain yield (r = 0.94, p<0.01) than with grain weight (r = -0.39 ns ). The higher number of grains per square meter was better correlated with the number of grains per spike in the modern cultivars than in the older ones. The genetic gain in grain yield was 44.9 kg ha -1 per year, reflecting important efforts of the breeding programs carried out in Southern Brazil. Grain yield changes, during the period of study, were better associated with biomass production (r = 0.78, p<0.01) than with harvest index (r = 0.65, p<0.01).

INFLUÊNCIA DE CULTURAS DE INVERNO SOBRE O RENDIMENTO DE GRÃOS DE SOJA CULTIVADA EM SISTEMAS DE ROTAÇÃO DE CULTURAS

Different preceding crops on the yield and height of soybean plants was assessed during nine years at EMBRAPA-Centro Nacional de Pesquisa de Trigo (CNPT), in Passo Fundo, RS, Brazil. The treatments consisted of seven crop systems, and soybean was sown in succession to white oat, black oat, flax, and wheat. Two plots were added in 1990; one to complement system II and the other as winter fallow preceding soybean (system VII). Winter crops were set up using conventional soil preparation, and summer crops were sown under no-tillage. An experimental design of blocks at random, with three replications and plots totalling 30m2, was used. The grown soybean after flax, in the mean of the period 1987 to 1989, in systems IV and VI showed lower plant on height and lower yield. No significant differences were found on the evoluated preceding crops on the yield over the periods 1990 to 1992 and 1993 to 1995. The grown soybean after white oat, black oat or wheat may be included in the different systems studied without any adverse effect.

Rendimento de grãos de soja em função de diferentes sistemas de manejo de solo e de rotação de culturas

O objetivo do presente trabalho foi avaliar sistemas de manejo de solo e de rotacao de culturas sobre o rendimento de graos e componentes do rendimento de soja durante seis anos. Foram comparados quatro sistemas de manejo de solo - 1) plantio direto, 2) cultivo minimo, no inverno e semeadura direta, no verao, 3) preparo convencional de solo com arado de discos, no inverno e semeadura direta, no verao e 4) preparo convencional de solo com arado de aivecas, no inverno e semeadura direta, no verao - e tres sistemas de rotacao de culturas: sistema I (trigo/soja), sistema II (trigo/soja e ervilhaca/milho ou sorgo) e sistema III (trigo/soja, ervilhaca/milho ou sorgo e aveia branca/soja). O delineamento experimental foi de blocos ao acaso, com parcelas subdivididas e tres repeticoes. O rendimento de graos e o peso de 1.000 graos de soja cultivada sob plantio direto e sob cultivo minimo foi superior ao de soja cultivada sob preparo convencional de solo com arado de discos e com arado de aivecas. A maior estatura de plantas de soja ocorreu no plantio direto. O rendimento de graos de soja cultivada apos trigo, no sistema II, foi superior ao de soja cultivada apos aveia branca e apos trigo, no sistema III, e apos trigo, no sistema I. O menor rendimento de graos, peso de graos por planta de soja e peso de 1.000 graos ocorreu quando em monocultura (trigo/soja).

CONVERSÃO E BALANÇO ENERGÉTICO DE SISTEMAS DE SUCESSÃO E DE ROTAÇÃO DE CULTURAS

Energy conversion and balance of seven crop rotation systems for wheat were assessed from 1987 to 1995, in Passo Fundo, RS, Brazil. The following systems were evaluated: system I (wheat/soybean); system II (wheat/soybean, from 1987 to 1989, and wheat/soybean and common vetch/corn or sorghum, from 1990 to 1995); system III (wheat/soybean, black oats or white oats/soybean, and common vetch/corn or sorghum); system IV (wheat/soybean, white oats/soybean, flax/soybean, and common vetch/corn, from 1987 to 1989, and wheat/soybean, sunflower or black oats/soybean, white oats/soybean, and common vetch/corn or sorghum, from 1990 to 1995); system V (wheat/soybean, wheat/soybean, black oats or white oats/soybean, and common vetch/corn or sorghum); system VI (wheat/soybean, wheat/soybean, white oats/soybean, flax/soybean, and common vetch/corn, from 1987 to 1989, and wheat/soybean, wheat/soybean, sunflower or black oats/soybean, white oats/soybean, and common vetch/corn or sorghum, from 1990 to 1995); and VII (winter fallow/soybean, from 1990 to 1995). On the average from1987 to 1989, no significant differences among rotation systems were observed for energy conversion and energy balance rates. From 1990 to 1995, system II (8.58) showed greater energy conversion index than system I (5.61), and the remaining systems did not differ significantly among themselves. From 1990 to 1995, systems II (20,938Mcal/ha), III (19,239Mcal/ha), IV (18,618Mcal/ha), V (19.646Mcal/ha), and VI (18,702Mcal/ha) showed greater energy balance, as compared to system VII (10.279kg/Mcal).

Conversão e balanço energético de sistemas de rotação de culturas para triticale, sob plantio direto

Efficient energy conversion production systems are important for modern agriculture. The objetive was to evaluate the energy conversion and balance of five rotation systems that included triticale. The evaluated systems, from 1987 to 1991, were: I (triticale/soybean), II (triticale/soybean and black oats/soybean), III (triticale/soybean and common vetch/corn), IV (triticale/soybean, common vetch/corn, and black oats/soybean), and V (triticale/soybean, triticale/soybean, common vetch/corn, and black oats/ soybean). In 1990, black oats was replaced by white oats in systems II, IV, and V. The experiment was set up under no-tillage, using a randomized block design with three replications and plots totalizing 24 m2 . On average, for the period 1987 to 1989, system III showed higher energy conversou (9.30) and balance (23.860 Mcal/ha), as compared to the othen studied systems (I: 5.38, II: 5.02, IV: 8.12 e V: 7.37; I: 18.067 Mcal/ha, II: 13.790 Mcal/ha, IV: 19.875 Mcal/ha e V: 19.264 Mcal/ha, respectivily). In this period, the climatic conditions were normal. On average, the period 1990 to 1991, there were no significant differences between energy conversion and balance means. In this period, climatic conditions were adverse.

Lucratividade e risco de sistemas de manejo de solo e de rotação e sucessão de culturas

Crop rotation and succession systems lesser the risk level due to diversification of cultivities. Soil tillage and crop rotation and succession systems were assessed in Passo Fundo, RS, Brazil, from 1994/95 to 1997/98. Four soil tillage systems - 1) no-tillage, 2) minimum tillage, 3) conventional tillage using a disk plow, and 4) conventional tillage using a moldboard plow - and three crop rotation and succession systems [system I (wheat/soybean), system II (wheat/soybean and common vetch/sorghum or corn), and system III (wheat/soybean, common vetch/sorghum or corn, and white oats/soybean)] were compared. An experimental design of randomized blocks with split-plots and three replications was used. The main plot was formed by the soil tillage systems, while the split-plots consisted of the crop rotation and succession systems. Two types of analysis were applied to the net return of soil tillage and crop rotation and succession systems: mean-variance and risk analysis. By the mean-variance analysis, no-tillage and minimum tillage, which presented higher net return, were the best alternatives to be offered to the farmer. By the stochastic dominance analysis, no-tillage and crop rotation with two winters without wheat showed the highest profit and the lowest risk.

Analise de risco em quatro sistemas de rotacao de culturas para trigo, num periodo de dez anos, em Passo Fundo, RS.

During ten years (1980 to 1989), at the Embrapa-Centro Nacional de Pesquisa de Trigo (CNPT), in Passo Fundo, RS, Brazil, the effects of crop rotation systems on wheat (Triticum aestivum L.) were assessed. Four rotation systems for wheat were studied: system I (wheat/soybean); system II (wheat/soybean, rapeseed/soybean, barley/soybean, lupine or serradella/corn); system III (wheat/soybean, arrowleaf clover/arrowleaf clover, and arrowleaf clover/corn, from 1980 to 1983, and wheat/soybean, white oats/soybean, and common vetch/corn, from 1984 to 1989); and system IV (wheat/soybean, rapeseed/soybean, flax/soybean, and lupine or serradella/corn). A randomized complete block design, with four replications and plots with 120 m2, was used. Risk analysis over that period is presented in this paper. Two types of analysis were applied to the net return of the systems: mean-variance analysis and risk analysis (safety-first and stochastic dominance). By the mean-variance analysis, systems II and IV showed higher net returns as compared to systems I and III. The system II showed the highest profit and the lowest risk to be offered to the farmer, as compared to the remaining systems studied.

Sistemas de produção alternativos de triticale, sob plantio direto, em Passo Fundo, RS

From 1987 to 1991, in Passo Fundo, RS, Brazil, the effects of production systems on triticale crop were assessed at the Centro Nacional de Pesquisa de Trigo. Five systems for triticale were studied: system I (triticale/soybean), system II (triticale/soybean and black oats/soybean, from 1987 to 1989, and triticale/soybean and white oats/soybean, from 1990 to 1991), system III (triticale/soybean and common vetch/corn), system IV (triticale/soybean, black oats/soybean and common vetch/corn, from 1987 to 1989, and triticale/soybean, common vetch/corn and white oats/soybean, from 1990 to 1991), and system V (triticale/soybean, triticale/soybean, black oats/soybean and common vetch/corn, from 1987 to 1989, and triticale/soybean, triticale/soybean, common vetch/corn and white oats/soybean, from 1990 to 1991). An experimental design of blocks at random with three replications and plots with 24 m2 was used. Economic analysis over that period is presented in this paper. Over the period in which the climatic conditions were normal, system III was the best alternative to be offered to farmers from profitability standpoint. When climatic conditions were adverse, system II showed higher economic return, as compared to the remaining systems studied.

EFEITO DE PRÁTICAS CULTURAIS SOBRE O RENDIMENTO E OUTRAS CARACTERÍSTICAS AGRONÔMICAS DE TRIGO ( 1 )

O objetivo deste trabalho foi avaliar os efeitos de praticas culturais sobre o rendimento de graos e algumas caracteristicas agronomicas de plantas de trigo. Foram comparados quatro sistemas de manejo de solo, a saber: 1) plantio direto; 2) cultivo minimo; 3) preparo convencional de solo com arado de discos mais grade de discos e 4) preparo convencional de solo com arado de aivecas mais grade de discos, e tres sistemas de rotacao de culturas: sistema I (trigo/soja), sistema II (trigo/soja e ervilhaca/milho ou sorgo) e sistema III (trigo/soja, aveia branca/soja e ervilhaca/milho ou sorgo). O delineamento experimental foi em blocos ao acaso, com parcelas subdivididas e tres repeticoes. A parcela principal foi constituida pelos sistemas de manejo de solo, e as subparcelas, pelos sistemas de rotacao de culturas. O rendimento de graos e a altura de plantas de trigo cultivadas sob plantio direto e sob cultivo minimo foram superiores ao trigo cultivado sob preparo convencional de solo com arado de discos e arado de aivecas. A maior massa de mil graos de trigo ocorreu no plantio direto. A rotacao de culturas foi eficiente na reducao de doencas do sistema radicular, resultando em aumento do rendimento de graos de trigo. O menor rendimento de graos, massa de graos, massa de mil graos e peso do hectolitro ocorreu quando trigo foi cultivado em monocultura (trigo/soja).

Crop Rotation and Tillage Systems to Control Root Rot and Leaf Spot Diseases of Wheat in Brazil

Soil degradation under conventional tillage is a major ecological problem in Brazil. It has been reported that more than 240 million tons of soil were lost every year in the southernmost Brazilian state up to the end of the 1980 decade due to excessive soil cultivation and heavy rainfall. To prevent erosion farmers were recommended to adopt no-till with debris preserving practices. However, the maintenance of crop residues on soil surface promotes a suitable environment for survival and rapid increase of necrotrophyc pathogens. Tests of crop rotation and soil tillage systems were carried out in Passo Fundo, State of Rio Grande do Sul, Brazil, over the past ten years, aiming to control root rot and leaf spot diseases of wheat. The incidence of leaf spot diseases was reduced by crop rotation, but their severity was not. Nevertheless, crop rotation and tillage systems significantly reduced root rots and increased wheat yields. Although chisel plowing was efficient in controlling root rots and increasing wheat yield, the benefits of disease control by incorporating crop residues into the soil by plowing do not justify the high risk of soil erosion losses.