Total Above-ground Dry Matter Research Articles

Productivity and nutrient use efficiency with integrated fertilization of buckwheat\u2013fenugreek intercrops

Intercrops and organic fertilizers can improve the productivity of cropping systems due to increased soil nutrient availability and plant nutrient use efficiency. A 2-year field experiment was conducted to determine the effects of different intercropping ratios and fertilizer types on nitrogen (N) and phosphorus (P) concentrations and yields of fenugreek and buckwheat at the research farm of Shahrekord University, Iran. The treatments consisted of sole cropping of fenugreek (F), buckwheat (B) and three intercropping ratios (F:B = 1:2, 1:1 and 2:1) under three fertilizer types: chemical fertilizer (CF), integrated fertilizer (IF) and broiler litter (BL). At flowering and at harvest, intercropping increased total above-ground dry matter (TAGDM), total seed yield, N and P concentrations (plant) and uptake. The applied N use efficiency and applied N recovery efficiency (ANUE, ANRE) in the intercropped plots were also higher as compared to the sole cropping. The intercropping ratio of F:B (2:1) was the most suitable for improving the tested nutrient variables. The IF and BL showed significant benefits as compared to CF, for TAGDM, total seed yield, NC and PC in the plant, as well as N and P uptake in sole and intercrops. For ANUE and ANRE, CF proved to be more effective. This study showed that a 2:1 fenugreek–buckwheat intercropped system with the application of IF and BL can successfully be implemented for improving productivity, N and P contents of fenugreek and buckwheat as well as the nutrient land equivalent ratio (compared with sole cropping with CF) under semi-arid growing conditions.

How does STICS crop model simulate crop growth and productivity under shade conditions?

Most crop models have been developed with crops growing under full sunlight conditions and they commonly use daily cumulated global radiation as part of the climatic input data. This approach neglects the spatio-temporal dimension of the light reduction experienced by the crop in agroforestry systems. In this study, we evaluate the ability of the crop model STICS to predict winter wheat (Triticum aestivum L.) growth and yield under three distinct light conditions using field observations from a two year artificial shade experiment. The shade structure induced a continuous shade (CS) treatment characterized by a reduction of the proportion of light during the entire day and a periodic shade (PS) treatment defined by an intermittent shade varying on the plot throughout the day. These two shade conditions were compared to a no shade treatment (NS) receiving 100% of the available light. The model accurately predicted the timing of the grain maturity stage under the PS treatment by reducing the daily global radiation only. A correct prediction of this growth stage in the CS treatment required a decrease of the daily maximum air temperature in addition to the reduction of global radiation. Overall, the model accurately reproduces the total aboveground dry matter dynamics under the CS and NS treatments, but did not simulate the reduction observed under the PS treatment correctly. Three parameters (nbjgrain, cgrain and cgrainvo) involved in the determination of the number of grains have been calibrated with the NS treatment data and were then used to predict the crop behavior under the shaded treatments. Using this adjusted parameter set, the STICS model gave a good prediction of the grain number under all treatments. Nevertheless, the simulation of final grain yield under the shade treatments was not satisfactory yet, presumably due to an overestimation of the reallocation of the biomass between shoots and grains. Improving the prediction of these reallocation processes is challenging and critical to improve the simulation of crop behavior under fluctuating light environments such as encountered in agroforestry systems.

Radiation efficiency and nitrogen fertilizer impacts on sunflower crop in contrasting environments of Punjab, Pakistan.

Sunflower (Helianthus annuus L.) is the leading non-conventional oilseed crop in Pakistan. Nitrogen fertilizer can affect plant growth and productivity by changing canopy size which has an effect on the radiation use efficiency (RUE) of the crop. The response of sunflower hybrids in terms of phenology, fraction of intercepted radiation (F i), and RUE to nitrogenous rates (0, 60, 120, 180, and 240kgha-1) was studied in three field experiments conducted in three various environments: Multan (arid), Faisalabad (semi-arid), and Gujranwala (sub-humid) during spring seasons 2008 and 2009. The treatments were laid out according to a randomized complete block design with split plot arrangements, keeping the sunflower hybrids in main plots and nitrogen rates in sub-plots, and replicated three times. The results showed Hysun-38 took a maximum number of days to anthesis (101) as compared to Pioneer-64A93 (100) and Hysun-33 (99). The mean values of F i were 0.850, 0.903, and 0.978, and the estimated values of RUE for total aboveground dry matter were 2.14, 2.47, and 2.65gMJ-1 at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The values of RUE for grain yield (RUEGY) were 0.78, 0.98, and 1.26gMJ-1 at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The average RUEGY values over three locations were 2.61, 2.60, 2.43, and 2.36gMJ-2 in N4 (180kgha-1), N5 (240kgha-1), N3 (120kgha-1), and N2 (60kgha-1) treatments, respectively. Increasing rates of N increased RUEGY over the standard treatment N3 (120kg Nha-1); however, the averaged values over three locations were 1.22, 1.08, 0.99, and 0.92gMJ-2 in N4, N5, N3, and N2 treatments, respectively. Therefore, optimum water and N doses are important for attaining higher RUE, which may enhance sunflower growth and yield.

Effects of best management practices on dry matter production and fruit production efficiency of oil palm

Abstract Enhancing dry matter production with higher partitioning to fruit bunches is important for sustainable intensification of oil palm. A series of best management practices including site-specific nutrient management, canopy management, and harvesting has been developed for oil palm plantations. However, the effects of these practices on dry matter production and partitioning, and how the effects vary with climatic and soil conditions of plantation sites, remain largely unknown. We established a four-year field trial including 30 paired commercial blocks across Sumatra and Kalimantan, Indonesia. The paired treatments included site-specific best management practices, and standard estate practices as the control. The annual production of aboveground dry matter was 30.0 ± 0.5 t ha−1 yr−1 (mean ± se) under best management practices, higher than 28.8 ± 0.5 t ha−1 yr−1 under standard estate practices. The bunch index, an indicator of the fruit production efficiency, increased by 12% under best management practices compared to standard estate practices. Partitioning of dry matter to the fronds decreased by 8% under best management practices, compared to standard estate practices. The positive effect of best management practices on the annual production of total aboveground dry matter was stronger in the plantation site with higher annual rainfall. These results are useful for optimizing management practices to improve sustainable intensification of oil palm.

Cultivar Stevia rebaudiana Bertoni em Bragança: orientações para a técnica cultural

Stevia [Stevia rebaudiana Bertoni] is a crop expanding worldwide due to the increasing use in the food industry. The aims of this work were to check the adaptation of Stevia to the ecological conditions of the northeast of Portugal and to assess the response of the plant to the application of different rates of nitrogen, phosphorus and potassium as fertilizers and two different cutting regimes, once and twice during the growing season. The field trials were carried out in Bragança and Vilariça valley, both located in NE Portugal but in very different ecological situations, respectively in one of colder and warmer places in the region. It was assessed the winter survival of stevia plants, as well as dry matter yield, tissue elemental concentration and several vegetation indices. The results revealed that the plants did not survive the winter, with mortality exceeding 95%, meaning that Stevia can only be grown as an annual crop, which requires the installation of the new fields every year. The dry matter yield significantly increased with nitrogen rate. In the most productive treatment (100 kg N/ha), 1560 kg/ha of dry leaves and 4961 kg/ha of total aboveground dry matter (leaves + stems) were reached. Leaf nitrogen concentration did not significantly varied with nitrogen rate, despite the increase observed in dry matter production, which may mean that difficulties can arise in monitoring the nitrogen nutritional status of plants in the field and in the establishment of adequate fertilization programs for this crop.

Yield and dry matter productivity of Japanese and US soybean cultivars

The difference in yields of cultivars may be causing difference in soybean yield between Japan and the USA. The objective of this study was to identify the effect of the cultivar on dry matter production and to reveal the key factors causing the differences in yield by focusing utilization of solar radiation in recent Japanese and US soybean cultivars. Field experiments were conducted during two seasons in Takatsuki, Japan (34°50′), and in a single season in Fayetteville (36°04′), AR, USA. Five Japanese and 10 US cultivars were observed under near-optimal conditions in order to achieve yields as close to their physiological potential as possible. The seed yield and total aboveground dry matter (TDM) were measured at maturity as long as radiation was intercepted by the canopy. The seed yield ranged from 3.10t ha−1 to 5.91t ha−1. Throughout the three environments, the seed yield of US cultivars was significantly higher than that of Japanese cultivars. The seed yield correlated with the TDM rather than the HI with correlation coefficients from .519 to .928 for the TDM vs. .175 to .800 for the HI, for each of the three environments. The higher TDM of US cultivars was caused by a higher radiation use efficiency rather than higher total intercepted radiation throughout the three environments. The seasonal change in the TDM observed in four cultivars indicated that dry matter productivity was different between cultivars, specifically during the seed-filling period.

Nitrogen and phosphorus nutrition and stoichiometry in the response of maize to various N rates under different rotation systems

Better understanding of plant nutrition and nutrient interactions is of critical importance for developing best management practices in crop production. A three-year study was conducted to examine N and P nutrition and their association in maize as affected by rotation system, N application rate and hybrid maize. Rotation by N treatments were composed of maize–alfalfa (MA), maize–soybean (MS) and continuous maize (MM), fertilized in maize year at 0, 50, 100 and 150 kg N ha−1, respectively. The two maize varieties were glyphosate-resistant (RR) non-Bt (non-Bt) and stacked RR + Bt near-isoline (Bt) hybrids. Our data showed that grain yield, stover, and total aboveground (or shoot) dry matter, N and P uptake (except for stover P) in amounts followed the order MA > MS > MM and were well responsive to N rates. Grain and shoot N and P contents of Bt maize was greater (P < 0.05) than those of non-Bt hybrid in MM. The N:P ratio was positively correlated with N application rates, and was greater in rotational maize than in MM. Both hybrids attained their maximum yields at approximately 201 kg ha−1 of grain N and 255 kg ha−1 of shoot N, corresponding to 36 and 43 kg P ha−1 in grain and shoot. Nitrogen harvest index, P harvest index and nutrient internal efficiency were responsive to N rates but were not different between the hybrids. This study revealed that the critical grain and shoot N content achieving maximum yield appeared to concomitantly result in high P contents.

PREDICCIÓN DEL CRECIMIENTO POTENCIAL DE TOMATE DE CÁSCARA MEDIANTE EL MODELO SUCROS

SUCROS (a Simple and Universal Crop Growth Simulator) is a mechanistic model, which explains crop growth based on process such as photosynthesis and respiration, under the influence of environmental conditions. The aim of the present research was to investigate to what extend the SUCROS model can predict potential growth and development of a husk tomatoes crop. In order to do that, model predictions of total above-ground dry matter, biomass of leaves, biomass of fruits, biomass of stems of the plants, and leaf area index, were compared against measurements that came from one potential crop growth experiment. In contrast to growth analysis, explanatory models, such as SUCROS, relate crop growth and development with fundamental physiological processes. Afterwards the model calibration was carried out, by adjusting the five model most sensitive parameters, the degree of fit among simulations and measurements was acceptable for almost all calibrated conditions, being (R2>0.92) in case of total above-ground dry matter, (R2>0.95) for biomass of stems, (R2>0.79) for leaves biomass, (R2>0.83) for fruits biomass and (R2>0.58) for the leaf area index.

Dry matter and nitrogen partitioning and translocation in winter oilseed rape (Brassica napus L.) grown under rainfed Mediterranean conditions

For crops grown in Mediterranean environments, translocation of pre-anthesis assimilates to the fruit is of great importance, because hot and dry conditions during fruit ripening diminish net assimilation rate and nitrogen (N) uptake. This field study was conducted to assess the pattern of dry matter and N accumulation and the role of assimilate translocation in pod development of oilseed rape plants in a Mediterranean environment. Four cultivars of winter oilseed rape (Brassica napus L.), i.e. three hybrids (Royal, Exact, Excalibur) and an inbred line (Fortis), were grown for two growing seasons (2005–06 and 2006–07) in northern Greece. On average, 581, 1247, 1609, and 2749 growing degree-days (GDD) were required for six leaves, stem elongation, 50% anthesis in main stem, and physiological maturity in the first year, and 539, 1085, 1601, and 2728 GDD in the second year. The R2 of the modified Richards function indicated that aboveground biomass and N accumulation were described with high approximation efficacy. The across-cultivars genotype mean maximum predicted total aboveground dry matter and N content were 1368.8 and 21.4 g m–2 in 2006 and 1655.1 and 25.4 g m–2 in 2007. In 2007, dry matter and N translocation from vegetative tissues to pods were 464.4 and 21.0 g m–2, and significantly higher than the corresponding values recorded in 2006 (264.4 and 17.0 g m–2). These differences were due to greater amounts of dry matter and N accumulating at anthesis and the greater sink capacity of plants (pod number) in 2007. The fact that pod development occurred in a period when N accumulation by oilseed rape plants had stopped led to high values of contribution of pre-anthesis N accumulation to pod N content in both years (92.8% in 2006 and 96.6% in 2007). Results indicated that hot and dry weather post anthesis reduced dramatically the net assimilation rates; thus, translocation of pre-anthesis assimilates was crucial for pod development. The results demonstrate that variation in weather conditions between growing seasons is one of the main causes of seasonal variation in oilseed rape productivity under Mediterranean conditions.

Accumulation and translocation of dry matter and nitrogen in different purple corn hybrids ( Zea mays L.)

In this study, five purple corn hybrids (ZS7615, ZF7139, FS7011, FG5701, 68G1) and one commercial grain hybrid ZD958 were studied to investigate the changes in accumulation, partitioning and translocation of dry matter and N. Results indicated that the total aboveground dry matter of all hybrids increased from anthesis to maturity. Conversely, the dry matter of vegetative organs significantly decreased. All hybrids exhibited an obvious trend of decrease in concentrations of N from seedling stage to maturity. However, N accumulations had reversely changes. Of all the purple corn hybrids, the hybrid 68G1 had a relatively higher grain yield, grain N and dry matter of husk and cob which had the highest anthocyanins. The harvest index and N harvest index of 68G1 were also higher than other purple corn hybrids. There was a significant correlation between grain yield and harvest index and grain N. The findings are helpful to make a nutrient regime recommendation for purple corn production. It also suggests a further genetic improvement for breeding new purple corn hybrid which had both higher grain yield and aboveground dry matter. Key words: Purple corn, dry matter, nitrogen, partitioning, anthocyanins.

Competitive ability of Rhinanthus minor L. in relation to productivityin the Rengen Grassland Experiment

Rhinanthus minor (yellow-rattle) can be used for restoration of species-rich grasslands but is vulnerable to competitive exclusion from high total aboveground biomass production of vascular plants. We asked (1) whether there is a threshold limit for total annual aboveground biomass production of vascular plants above which R. minor cannot establish viable population in grasslands and (2) how is cover of R. minor in grassland related to standing biomass of bryophytes. Data were collected in the Rengen Grassland Experiment (RGE) established in Germany in 1941 with following fertilizer treatments: unfertilized control, application of Ca, CaN, CaNP, CaNPKCl and CaNPK&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;. Cover of R. minor and total annual aboveground biomass production of vascular plants were determined from 2005 to 2009. Further relationship between standing biomass of bryophytes and cover of R. minor was analyzed in 2006. Mean cover of R. minor over five years ranged from 0.7% to 12.3% in CaNPK&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; and control treatments, respectively. Cover of R. minor was significantly negatively related to total annual aboveground biomass production of vascular plants and cover of R. minor was below 3% in all plots with total annual aboveground dry matter biomass production of vascular plants higher than 5 t/ha. Although cover of R. minor was markedly reduced in highly productive plots in the RGE, high standing biomass of bryophytes (1.8 t/ha) in low productive control was not an obstacle for establishment of its viable population. We concluded, that viable population of R. minor can be established in grasslands only if total annual aboveground dry matter biomass production of vascular plants is below 5 t/ha regardless on standing biomass of bryophytes.

Effect of Thinning on the above Ground Biomass of (Conocarpus erectus L.) Trees in the Western Region of Saudi Arabia

Benefiting from introduced exotic trees in Saudi Arabia is mostly limited to municipal uses. In order to establish forest plantations of those species, studies should be conducted concerning the effect of silvicultural practices on the plantations productivity. In the present study, we studied the effect of three thinning treatments, on 7 years old short rotation intensively cultured Buttonwood (Conocarpus erectus L.) plantation after 2 years of application. The thinning treatments were 0, 50 and 67% of stock. In exception of the increase in the dry matter (DM) of foliage, no significant influence of thinning was observed on the above ground dry matter (AGDM) of individual tree components. The average total above ground dry matter (TAGDM) ranged between 15.79 kg for unthinned to 22.44 kg for 67% treatment. In all treatments, stem wood accounted for the largest proportion of AGDM with the highest value for the unthinned (71.72 %), differing significantly from the other two treatments (62.88 and 63.05%). Of all tree dimension parameters, only crown diameter (CrD) and stand basal area (BA) were significantly influenced by the treatments. The 67% thinning treatment had the highest mean CrD (2.16 m), while the unthinned was the highest in BA (17.93 m2 ha-1). Several allometric equations were constructed relating DM of tree components and stem volume of individual trees with their diameter or diameter and total height. Except foliage DM all the relations were highly significant. The coefficients of determination (R2) were 0.882, 0.899, 0.945, 0.996, 0.987 and 0.990 for twigs, branches, bark, stem wood, total DM and stem volume respectively.

Maize varieties suitable for the production of biogas

The aboveground parts, grain yield, dry matter and water content of the silage maize varieties Bermasil (early) and Mv MSC 485 (mid-season) and the grain maize varieties Mv To 286 (early) and NKPX 9283 (mid-season) were analysed to determine how these traits should be modified to develop a variety type more suitable for the production of bioenergy, more particularly biogas. It was established that silage maize types are generally taller, with larger tassels, leaves, cobs and stalk mass below the ear, making them suitable for biogas production. It is important to note, however, that the grain yield of these varieties should not be ignored, as it makes up 40–50% of the total aboveground dry matter yield. As one of the earliest maturing varieties, the silage maize variety Bermasil could be suitable in itself for biogas production. Based on the present and earlier data, it can be concluded that varieties with later maturity dates than those generally used for silage production could also be suitable for biogas production, provided they reliably reach the “half milk line” stage of maturity and a grain moisture content of around 42% every year in the given environment.

Nitrogen dynamics following grain legumes and subsequent catch crops and the effects on succeeding cereal crops

The effects of faba bean, lupin, pea and oat crops, with and without an undersown grass-clover mixture as a nitrogen (N) catch crop, on subsequent spring wheat followed by winter triticale crops were determined by aboveground dry matter (DM) harvests, nitrate (NO3) leaching measurements and soil N balances. A 2½-year lysimeter experiment was carried out on a temperate sandy loam soil. Crops were not fertilized in the experimental period and the natural 15N abundance technique was used to determine grain legume N2 fixation. Faba bean total aboveground DM production was significantly higher (1,300 g m−2) compared to lupin (950 g m−2), pea (850 g m−2) and oat (1,100 g m−2) independent of the catch crop strategy. Faba bean derived more than 90% of its N from N2 fixation, which was unusually high as compared to lupin (70–75%) and pea (50–60%). No effect of preceding crop was observed on the subsequent spring wheat or winter triticale DM production. Nitrate leaching following grain legumes was significantly reduced with catch crops compared to without catch crops during autumn and winter before sowing subsequent spring wheat. Soil N balances were calculated from monitored N leaching from the lysimeters, and measured N-accumulation from the leguminous species, as N-fixation minus N removed in grains including total N accumulation belowground according to Mayer et al. (2003a). Negative soil N balances for pea, lupin and oat indicated soil N depletion, but a positive faba bean soil N balance (11 g N m−2) after harvest indicated that more soil mineral N may have been available for subsequent cereals. However, the plant available N may have been taken up by the grass dominated grass-clover catch crop which together with microbial N immobilization and N losses could leave limited amounts of available N for uptake by the subsequent two cereal crops.

Pasture - crop rotations for sustainable production in a wheat and sheep-based farming system on a Vertosol in south-west Queensland, Australia

Rainfed grain production, based on winter cereals, is marginal in south-west Queensland, Australia, because of low and variable rainfall and high evapotranspiration. Also, grain yield and grain quality have decreased as soil fertility, particularly soil nitrogen supply, has declined on older cropping lands. An option for improving soil N supply is to include legume-based pastures in rotation with winter cereals. The objective of this study was to determine the effects of short-term (18 months) legume pastures (annual medics and lucerne + annual medics), and longer term (3 years) mixed grass (Bambatsi panic) and legume (lucerne + annual medics) pasture phases on sheep production and on soil water and N supply and production of subsequent wheat crops on a grey Vertosol soil. Two separate phases of annual medics and lucerne + annual medics pastures produced mean total aboveground dry matter yield of 7.10 t/ha of annual medics and 5.80 t/ha of lucerne + annual medics over the 18-month periods. For two phases of the grass + legume pastures, mean total aboveground dry matter yield was 3.95 t/ha for grass and 8.19 t/ha for legume over 3 years. Over an 18-month period, sheep bodyweight gains and fleece weights were similar for the annual medics, lucerne + annual medics and grass + legume pastures and were approximately five times greater than those from native pasture as a result of the greater stocking rate possible on the sown pastures. Greater drying of the soil profile occurred following lucerne + annual medics and grass + legume pasture phases than continuous wheat, resulting in lower soil water content at sowing of wheat crops following these pasture phases on several occasions. Mean soil nitrate-N benefits before wheat sowing in the first year following termination of the 18-month annual medics, lucerne + annual medics, and the 3-year grass + legume pasture phases were 45, 44 and 42 kg N/ha, respectively. Grain N yields and gross margins of the first wheat crops following the 18-month annual medics, lucerne + annual medics, and the 3-year grass + legume pasture phases were similar in value to continuous wheat with ~60, 80, and 40–60 kg N/ha fertiliser applied at sowing, respectively. Improvements in grain N yield and gross margin were still evident in the fifth wheat crop following annual medics and lucerne + annual medics pastures and in the third wheat crop following grass + legume pasture, compared with continuous wheat without N fertiliser addition. Total gross margins from 1996 to 2005 were 1.6–2.5 times greater for the pasture–crop rotations than continuous wheat where no N fertiliser was applied to wheat. However, gross margins were greater in continuous wheat than in pasture–crop rotations where N fertiliser was applied to target prime hard grade grain protein in wheat. The 3-year grass + legume pasture phase showed potential to improve surface soil structure and water infiltration and to reduce decline in soil organic carbon concentration at 0–0.1 m depth, compared with continuous wheat cropping and shorter-term legume pasture phases.

Field evaluation of Amaranthus species for seed and biomass yields in southern Italy

Amaranth is a crop with a potentially increasing cultivation area. Little information is available on amaranth cultivation in Mediterranean environments and in southern Italy. The aim of this study was to evaluate the agronomic traits and assess the grain and biomass yield responses of 11 genotypes belonging to 5 Amaranthus species, provided from the USDA-ARS, National Plant Germplasm System. There was wide diversity in agronomic traits among Amaranthus species and among genotypes within the same species. The accessions belonging to A. cruentus had the shortest growing cycle followed by A. hybridus, A. hypochondriacus, A. caudatus and, finally, A. hybrid that had the longest growing season. The A. cruentus accessions reached maturity more quickly than the other species. The total above-ground dry matter ranged from 15 to 23 t ha-1 with A. cruentus, A. hypochondriacus, and A. hybridus being the most productive. The stem plus branches dry matter was well correlated to the plant height (r2 = 0.75**). The tested amaranth genotypes showed appreciable biomass production that can thus be regarded as an interesting secondary product after seed harvesting. Grain yield and components varied among species and accessions. A. hypochondriacus showed the highest yield per plant (55.4 g) followed by five accessions belonging to A. cruentus and A. hybridus (26.4 g on average). Considering together their shorter growing season and their higher grain production, the five accessions belonging to A. cruentus species appear to be better adapted to Mediterranean environments and southern Italy as compared to the other species.

Crescimento de frutos do meloeiro sob diferentes relações fonte: dreno

Um experimento foi realizado em ambiente protegido, de setembro de 2004 a janeiro de 2005, para avaliar o efeito da densidade de plantio e do número de frutos por planta no aumento da biomassa de frutos de meloeiro cultivado em substrato de casca de arroz crua e fertirrigado com solução nutritiva recirculada. Três densidades de plantio (1,7; 2,4 e 3,0 plantas m-2) e dois números de frutos por planta (3 e 4) foram estudados. A partir dos dados de matéria seca e fresca, aos 68 dias após o transplante, foram determinadas à produção e a distribuição de biomassa para os frutos. A matéria seca alocada nos frutos variou de 57 a 62% ao final do ciclo de cultivo, confirmando que, no meloeiro, estes são os maiores drenos de assimilados. A área foliar do meloeiro conduzido verticalmente e podado, ao final do cultivo, é relativamente baixa, o que associado a uma alta disponibilidade radiativa, evitou o excesso de sombreamento mútuo entre as plantas, mesmo na maior densidade de plantio. Assim, a maior densidade não afetou a distribuição de matéria seca e fresca para os frutos, aumentou a produção absoluta, por unidade de área, da biomassa da cultura e dos frutos. O aumento do número de frutos reduziu a matéria seca média dos frutos, sem afetar a produção e a distribuição de matéria seca total da planta e dos frutos. Entretanto, a produção e a distribuição de matéria fresca para os frutos assumem um comportamento diferente do da matéria seca, sendo ambas beneficiadas com tal incremento.

Growth and yield of barley in relation to grasshopper feeding damage

Grasshoppers are common pests of barley (Hordeum vulgare L.) in subarctic Alaska and cause substantial crop loss during outbreaks, but there is little information about the growth response of barley to grasshopper feeding damage. In two growth chamber experiments, we studied the effect of four densities (0, 1, 2, and 3 pot-1, equivalent to 0, 25, 50 and 75 grasshoppers m-2) of grasshoppers (Melanoplus sanguinipes F.) on the above-and below-ground growth of barley (eight plants per pot). Plants were exposed to grasshoppers beginning in the 3rd to 4th leaf stage (exp. 1) and in 1st to 2nd leaf stage (exp. 2). Plants were harvested and growth variables were measured shortly after anthesis and at maturity. Generally, the reduction in above-ground dry matter, at the highest density was 29 and 47% for exp. 1 and exp. 2, respectively. Effects of grasshoppers on below-ground growth (dry matter and surface area of roots) was less consistent than on above-ground variables; however, at the highest grasshopper density in exp. 2, dry matter and surface area of roots were reduced by about 40–53%.Grain yield (pooled over experiments) decreased by 19 and 36% for grasshopper densities of 2 and 3 pot-1, respectively. Most of the yield loss was accounted for by reduced seed weights, while protein content per seed remained nearly constant. The proportion of total above-ground dry matter represented in harvested grain and root:shoot ratios were not affected by grasshopper feeding. These results provide greater understanding of plant responses to insect feeding damage and will lead to more accurate estimates of economic injury levels. Key words: Cropyield loss, economic injury level, harvest index, Insecta

Seasonal changes in the effects of free-air CO 2 enrichment (FACE) on dry matter production and distribution of rice ( Oryza sativa L.)

It is reported that stimulating effect of elevated atmospheric [CO 2] on photosynthesis of rice ( Oryza sativa L.) is likely to be reduced during the plant growth period. However, there is little information on seasonal changes in dry matter (DM) production and distribution of rice under elevated atmospheric [CO 2]. A free-air CO 2 enrichment (FACE) experiment was conducted at Wuxi, Jiangsu, China, in 2001–2003, using Wuxiangging 14, a japonica cultivar. The rice was grown at ambient or elevated (ca. 200 μmol mol −1 above ambient) [CO 2] and supplied with 25 g N m 2, which is the normal N application rate for local farmers. DM accumulation of rice in FACE plots was significantly increased by 40, 30, 22, 26 and 16% on average at tillering, panicle initiation (PI), heading, mid-ripening and grain maturity, respectively. Rice DM production under FACE was significantly enhanced by 41, 27, 15 and 38% on average during the growth periods from transplanting to tillering (Period 1), tillering to PI (Period 2), PI to heading (Period 3) and heading to mid-ripening (Period 4), respectively, but significantly decreased by 25% in the period from mid-ripening to grain maturity (Period 5). In general, seasonal changes in crop response to FACE in both green leaf area index (GLAI) and net assimilation rate (NAR) followed a similar pattern to that of the DM production. Under FACE the leaves decreased significantly in proportion to the total above-ground DM over the season, the stems showed an opposite trend, while the spikes depended on crop development stage: showing no change at heading, significant increase (+4%) at mid-ripening and significant decrease (−3%) at grain maturity. Grain yield was stimulated by an average of 13% by FACE, due to increased total DM production rather than any changes in partitioning to the grain. We conclude that the gradual acclimation of rice growth to elevated [CO 2] do not occur inevitably, and it could also be altered by environmental conditions (e.g., cultivation technique).

Yield formation in Nicaraguan landraces of common bean compared to bred cultivars

Dry matter accumulation and its partitioning to different plant components were studied in six common bean populations (two bred cultivars and four landraces) with different yield potentials. The hypothesis that yield was correlated with leaf area or mass and also with leaf area duration was tested. Leaf area and total above-ground dry matter were sampled weekly between 13 and 62 days after planting (DAP). Yield, yield components and seed yield rate were measured at the final harvest. No differences in total above-ground dry matter were observed among populations up to 62 DAP. Bred cultivars had significantly larger leaf areas than the landraces at the last harvest. Landraces initially partitioned more dry matter to reproductive organs but this was not reflected in higher yields. Temporary differences in growth rate and rate of pod formation were observed among the populations. Landraces, with one exception, tended to grow faster at early stages, and they also reached their maximum number of pods per plant earlier than the bred cultivars. Bred cultivars yielded more than all but one of the landraces. In general, yield was positively correlated with the total number of pods per plant, which in turn was well correlated with leaf area and mass. It was concluded that an increase in leaf area duration and a balanced development of reproductive organs v. other plant components are important traits in conferring improvement in yield of common bean.