Dry Matter Accumulation Patterns Research Articles

Differences in Dry Matter Accumulation and Distribution Patterns between Pre-Elite Seed and Certified Seed of Virus-Free Potato

Virus-free seed potatoes are generally divided into pre-elite seeds and certified seeds. To study the differences in dry matter accumulation and distribution between pre-elite seeds and certified seeds through a field randomized block two-factor experiment, pre-elite seeds and certified seeds of four varieties were selected to explore the differences in growth characteristics between the two levels of virus-free potatoes and to find a way to improve potato seed expansion efficiency. The results showed that the growth process of pre-elite seeds was slower and the growth period was longer than certified seeds. The dry matter accumulation of pre-elite seeds in various organs was lower than in certified seeds, and the distribution ratio in the roots and stems of each variety was also lower than the certified seed, while there was no significant difference in the leaf and tuber distribution ratio. The average dry matter accumulation rate in both pre-elite and certified seeds was sorted by size of tubers > leaves > stems > roots; however, it was significantly lower in pre-elite seeds than in certified seeds. Tuber fresh weight, tuber volume, tuber number, and the theoretical yield of certified seeds were higher than those of pre-elite seeds. Experiments have shown that appropriately prolonging the harvest time of virus-free potatoes, especially pre-elite seeds, and increasing the proportion of dry matter allocated to roots and stems by pre-elite seeds in the early growth stages can effectively increase yield.

Comparison of fruit morphology and nutrition metabolism in different cultivars of kiwifruit across developmental stages.

Kiwifruit (Actinidia) is becoming increasingly popular worldwide due to its favorable flavour and high vitamin C content. However, quality parameters vary among cultivars. To determine the differences in quality and metabolic parameters of kiwifruit, we monitored the growth processes of ‘Kuilv’ (Actinidia arguta), ‘Hongyang’ (Actinidia chinensis) and ‘Hayward’ (Actinidia deliciosa). We found that ‘Kuilv’ required the shortest time for fruit development, while ‘Hayward’ needed the longest time to mature. The fruit size of ‘Hayward’ was the largest and that of ‘Kuilv’ was the smallest. Furthermore, ‘Hongyang’ showed a double-S shape of dry matter accumulation, whereas ‘Kuilv’ and ‘Hayward’ showed a linear or single-S shape pattern of dry matter accumulation during development. The three cultivars demonstrated the same trend for total soluble solids accumulation, which did not rise rapidly until 90–120 days after anthesis. However, the accumulation of organic acids and soluble sugars varied among the cultivars. During later fruit development, the content of glucose, fructose and quinic acid in ‘Kuilv’ fruit was far lower than that in ‘Hongyang’ and ‘Hayward’. On the contrary, ‘Kuilv’ had the highest sucrose content among the three cultivars. At maturity, the antioxidative enzymatic systems were significantly different among the three kiwifruit cultivars. ‘Hongyang’ showed higher activities of superoxide dismutase than the other cultivars, while the catalase content of ‘Hayward’ was significantly higher than that of ‘Hongyang’ and ‘Kuilv’. These results provided knowledge that could be implemented for the marketing, handling and post-harvest technologies of the different kiwifruit cultivars.

Source sink relationship, dry matter and starch partitioning in developing ginger rhizomes during different growth stages

Source sink relationship, dry matter and starch partitioning, rhizome bulking process in relation to dry matter and starch partitioning in developing rhizomes and growth and gas exchange parameters were studied in three popular varieties of ginger viz., IISR Varada, IISR Mahima and IISR Rejatha. Results revealed that maximum tiller production and leaf area accumulation occurred between 60 and 120 days after planting (DAP) in all three varieties. Photosynthetic rate and hormone contents (auxin and cytokinin) increased from 90-120 DAP, peaked at 120 DAP and then started declining. Biomass partitioning data revealed that the active biomass accumulation stage was between 60 and 150 DAP in ginger. The dry matter accumulation pattern in rhizomes also revealed that maximum dry matter accumulation in rhizomes also occurred between 60 and 150 DAP in all the three varieties. Maximum starch accumulation in the rhizomes also occurred during the same period. These results suggest that most of the rhizome bulking process occurred between 60 and150 DAP in ginger. Total biomass accumulation, dry matter accumulation and starch accumulation in rhizomes followed similar trends.

Additional variability in engineered Cowpea (Vigna unguiculata (L.) Walp) exposed to alpha-spin nano particles

Field study was conducted at the Botanical Garden, Federal University of Lafia, between August and October 2017 to investigate the effect of alpha nano spin on nine advanced varieties of cowpea obtained from Institute of Agriculture Research (IAR), Zaria and one local variety from Nasarawa Agricultural Development Program (NADP), Lafia which served as the control. These seeds were exposed to alpha-spin nano-particles at four different periods; 20 mins, 40 mins and 60 mins termed as T1, T2 & T3 respectively while the untreated seeds 0 mins were termed T0 (control). The experimental design was a Randomized Complete Block Design with four replications. Data were collected on agronomic traits, yield components and grain yield, which were subjected to Analysis of Variance and Principal Component Analysis. Laboratory studies were also carried out to determine the pattern of Dry matter accumulation at two weeks interval for six weeks. Results of harvested seeds revealed that Sampea 5, inoculated at 40 mins treatment produced black seeds colour from brown seed colour parent. Results also showed a significant difference among treatments and varieties for mean plant height, the mean number of leaves, mean number of pods and mean pod length. Total dry matter accumulation of leaves, 100 disc leaves and stems over time varied among treatments and varieties. The first three Principal Components (PCs) accounted for 83.1% of the total variation implying their high selection stability. The detailed results are presented and discussed in this paper as a measure of the future selection of useful variants of the improved cowpea for sustainable cowpea production.

Pattern of Growth and Dry Matter Accumulation in Some Improved Cowpea Varieties (<i>Vigna unguiculata</i>) Exposed to Alpha Nano Spin

Ten (10) cowpea varieties exposed to alpha nano spin were evaluated during the 2019 cropping season to access the role of alpha nano spin in their growth and dry matter accumulation at the Botanical garden of Federal University, Lafia. A Randomized Complete Block Design (RCBD) with four replications was used. The fourth replication was used for the destructive sampling over time. The seed was exposed to alpha nano spin before planting at 0, 20, 40 and 60 minutes respectively. Results of the study showed that the varieties differed significantly with respect to morphological traits studied (P s such as vine length, number of leaves and above ground stems were significantly influenced by alpha nano spin bombardment. 40 mins alpha nano spin resulted in maximum accumulation of dry matter, leaf area and leaf area index. The traits evaluated were stable under alpha nano spin exposure, suggesting that they could be useful indices in creating genetic variability in each of the varieties.

Dry matter accumulation and nutrient uptake patterns of onion seed crop

Dry matter accumulation and nutrient uptake patterns of crops must be determined to optimize fertilizer scheduling. This study assesses the dry matter accumulation and nutrient uptake patterns of onion seed crop. Plant samples were collected between 0 and 120 days after planting, and their nutrient content was analyzed to determine the dry matter accumulation and nutrient uptake patterns. The quantity and period of nutrient uptake and the mobility of nutrients within the plant parts varied for different nutrients. The absorption of nitrogen (N) and potassium (K) was the highest during vegetative stage, whereas phosphorus (P) and sulfur (S) uptake was the highest during flower initiation stage. N, P, K, and S, which had accumulated in the vegetative parts, moved from the senesced vegetative parts to the inflorescence during the reproductive stages owing to their high mobility in the phloem. The onion plants continued to absorb zinc, copper, manganese, and iron throughout their growth owing to the immobility of these elements in plant system. The result of this study may facilitate efficient scheduling of fertilizer application to increase nutrient uptake and yield.

Selecting Best Double Sigmoid Function to Describe Growth and Growth Rate of Rapeseed Under Water Stress

Dry matter accumulation pattern of winter cereals and rapeseed is similar to double sigmoid growth curve and can be described by sum of two different or similar singular sigmoid (S-shape) functions (e.g., Richards, Von Bertalanffy, and other functions) that they have overlap on one point. In this study, accuracy of 49 different function compositions of double sigmoid function for describing the rapeseed dry matter based on days after planting (DAP) and growing degree days (GDD) were tested. Results of this study showed that the Beta–Richards and Richards–Gompertz functions were fitted to the measured dry matter during growing season very accurately based on DAP and GDD, respectively. Sum of two Von Bertalanffy or Weibull functions can not describe the winter rapeseed growth. Results of this investigation can be used to estimate dry matter of rapeseed during growing season and analysis of plant growth rate variation under different irrigation treatments.

Evaluation of dry matter accumulation in triticale by different sigmoidal growth models in west anatolia of turkey

Monitoring biological growth of field crops is important for planning and timing agricultural practices. In order to assess biological growth pattern of dry matter accumulation in triticale Egeyildizi triticale variety were grown in ?anakkale conditions in 2012-2013 and 2013-2014 growing seasons with continuous plant samplings from seedling emergence until seed maturation. Gompertz, Logistic, Logistic Power and Richards growth models are fitted to actual growth data and their predictions were compared. Results suggested that all sigmoidal growth models successfully explained triticale dry matter accumulation over 98 % R2 values and low mean square errors, Richards model fitted best for both years with an R2 value over 99 %. Dry matter accumulation were also investigated as a result of average temperature, precipitation, growth degree days and cumulative growth degree days with stepwise regression. Rresults indicated that average weather temperature had a similar pattern across both growing seasons and had a major influence on dry matter accumulation. Since Richards sigmoidal growth model may be adequately described growth pattern of triticale by generally high R2 with lower Mean Square Error (MSE) values.

Corn Era Hybrid Dry Matter and Macronutrient Accumulation across Development Stages

Core Ideas Evaluating corn dry matter and macronutrient accumulation patterns across era hybrids is necessary to understand changes in plant nutrient requirements and effects on accumulation timing and fertilization management. Era hybrids differed in dry matter and nutrient accumulation, with differences in nutrient content mainly related to dry matter production. Dry matter and P accumulation was linear, however, N and K accumulation slowed during the reproductive stages. Although the absolute dry matter production and nutrient content was greater with the most recent hybrids, relative to the maximum dry matter and N, P, and K content and the accumulation rate (cumulative growing degree unit‐based) remained the same across era hybrids. Results indicate that overall dry matter production and yield potential has been mainly responsible for changes in corn macronutrient requirements with development of new hybrids. Evaluating corn (Zea mays L.) aboveground dry matter (DM) and macronutrient accumulation patterns across era hybrids is necessary to understand changes in plant nutrient requirements and effects on accumulation timing and fertilization management. Two popular hybrids for each of five era‐decades from 1960 to 2000 were grown in 2007 and 2008. Whole plant samples were collected at 10 development stages, with dry matter (DM), N, P, and K determined. Era hybrids differed in DM and nutrient accumulation, with differences in nutrient content mainly related to DM production. The 1960 to 1990 era hybrids were more similar in DM and nutrient content across development stages compared to the 2000 era hybrids which had the greatest content. Dry matter and P accumulation was linear (V6–R5 stages), however, N and K accumulation slowed during the reproductive stages. While the fraction of maximum plant content at R1 averaged 48, 71, 58, and 83% across hybrids for DM, N, P, and K, respectively; the ranges were 43 to 52% for DM (1990 and 1960), 64 to 78% for N (1990 and 1960), 55 to 60% for P (2000 and1960), and 69 to 93% for K (1990 and 1960). Although the absolute DM production and nutrient content was greater with the most recent hybrids, relative to the maximum DM, N, P, and K content and the accumulation rate, growing degree unit based, remained the same across era hybrids. This indicates that overall DM production and yield potential has been mainly responsible for changes in corn macronutrient requirements with development of new hybrids.

Assessment of dry matter accumulation and nutrient uptake pattern of garlic

Field experiment was conducted to assess dry matter accumulation and nutrient uptake pattern of garlic. Plant samples were collected at 15 day interval from planting to harvest. The samples were partitioned, processed and analysed for macro and micronutrients. Results showed that total nutrients required to produce 6.7 t garlic bulbs/ha was 56.3 kg N, 13.5 kg P, 65.8 kg K, 30.6 kg S, 110.3 g Zn, 116.9 g Mn, 724.9 g Fe, and 26.2 g Cu. Garlic plants accumulated 84.7 and 84.6% of total nitrogen (N) and potassium (K) from planting to 75 days after planting (DAP). The peak N and K uptake coincided with the active vegetative growth stage. Whereas, the total phosphorus (P), sulphur (S), zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) uptake accounted for 59.5–66.7% of total uptake from planting to 75 DAP accounted. The peak uptake of these nutrients coincided with bulb initiation and development stages. Subsequently, an effective nutrient schedule could be developed for adoption by farmers.

Physiological characteristics, dry matter, and active component accumulation patterns of Changium smyrnioides in response to a light intensity gradient

Context: Changium smyrnioides Wolff (Apiaceae) is an endangered medicinal plant with numerous pharmacological uses. Objective: To investigate the effect of light intensity levels on the growth and accumulation of secondary metabolites of C. smyrnioides, cultivated seedlings were subjected to different relative light intensities via sun-shading. Materials and methods: Changium smyrnioides seedlings were subjected to five irradiance treatments (100, 60.54, 44.84, 31.39, and 10.56% sunlight) in glasshouse for 9 months. Enzymatic and non-enzymatic antioxidants with spectrophotometric method, photosynthetic parameters with Li-6400XT, dry matter accumulation and active component contents in the root with spectrophotometric and HPLC method were analyzed. Results: With an increase in relative light intensity levels, activities of enzymatic and non-enzymatic antioxidants, and malondialdehyde (MDA) contents were increased overall, while net photosynthetic rate (Pn) and dry matter accumulation patter first increased and then declined. The highest net photosynthetic rate (30.68 μmol/m2·s) and dry root weight (5.07 g) were achieved under 60.54% sunlight. Lower relative light intensity levels stimulated the accumulation levels of bioactive compounds in the roots so that the highest contents of mannitol (1.35%) and choline (405.58 μg/g) were recorded under 31.39% sunlight, and the highest polysaccharide content (10.80%) were achieved under 44.84% sunlight. With a decrease in the relative light intensity levels, the water-soluble component content increased first and then decreased. Discussion and conclusion: The results revealed that 31.39–60.54% sunlight serve as appropriate relative light intensity conditions for cultivated C. smyrnioides.

Genetic variability in storage root bulking of cassava genotypes under irrigation and no irrigation

Early bulking in cassava (Manihot esculenta Crantz) is a very important trait in semi-arid ecologies of the tropics. Farmers tend to select early-maturing cassava varieties to escape terminal drought and destruction by domestic animals during the dry season. However, early harvesting is associated with yield penalty due to unavailability of high-yielding early-maturing cassava varieties. In order to develop early-bulking cassava varieties for the savanna ecologies, this study was carried out to assess genetic variation in the pattern of storage root bulking and as well as traits associated with early storage root bulking under moisture stress and well-watered conditions. Twenty cassava genotypes were arranged in a randomised complete block design with three replications under irrigation and no irrigation. The genotypes were sequentially harvested at 6, 8, 10 and 12 months after planting to study their pattern of dry matter accumulation. Irrigation water was supplied using a drip irrigation system with a discharge capacity of 1.6 l/h. Analysis of variance indicated significant effect of genotype, harvesting time and irrigation on most of the yield traits studied. The interaction between genotype and irrigation effect was significant for all traits except mean storage root weight, storage root girth, storage root length and storage root dry matter content. Apart from storage root girth and storage root dry matter content, genotype × harvesting time interaction was not significant. Pearson correlation analysis of root yield at different times showed significant positive correlation between early storage root yield and final root yield indicating the possibility of selecting early-bulking genotypes with high yield potential. The study indicated that dry matter is partitioned more for root elongation than expansion in root girth under moisture stress conditions compared with irrigation, resulting in high storage root length: girth ratio. This ratio can be used to study the pattern of photosynthates accumulation in cassava roots under stress conditions. The study helped to provide improved understanding of the genetic basis and the mechanism of storage root bulking in cassava under moisture stress conditions, which can be exploited to develop high-yielding cassava varieties for drought-prone areas to ensure food security.

Metal, nutrient and biomass accumulation during the growing cycle of Miscanthus established on metal‐contaminated soils

AbstractThe energy crop Miscanthus presents high potentials for phytomanagement. Its shoot yield and nutrient accumulation has been extensively characterized in uncontaminated agricultural soils, while very little is known for metal‐contaminated conditions. This study aimed at assessing potential differences in dry matter and metal and nutrient accumulation of the standing aerial biomass in Miscanthus (M. × giganteus) growing in situ on agricultural plots presenting different soil Cd, Pb, and Zn concentrations. Plant samplings were conducted monthly along the growing period from May to December. Cadmium, Pb, Zn, and the concentrations of the nutrients N, P, K, Ca, Mg, and Na were determined in leaves and stems separately. During the growing phase, the maximum dry matter was reached in early in autumn. Whatever the organ, Cd and Zn concentrations were higher on contaminated than on uncontaminated plots. During summer and autumn, Zn and Pb concentrations were higher in leaves than in stems whereas Cd concentrations did not significantly differ between the organs. Concentrations of N, P, K, and Mg decreased across the study period whereas those of Ca and Na increased. Overall, metal and nutrient concentrations depended on plant organ and its development stage. The dry matter and nutrient accumulation patterns were not different between contaminated and uncontaminated plots. The significance of these findings is discussed in light of best phytomanagement practices and potential uses of Miscanthus biomass.

Influence of seed rates and levels of NPK fertilizers on dry matter accumulations and yield performance of foxtail millet (Setaria italica L. Beauv.)

A study was carried out in the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, Old Brahmaputra Flood Plains Soil (AEZ-9) during December 2001 to April 2002 to find out the effect of seed rates and NPK levels on dry matter accumulation and grain yield of foxtail millet (Setaria italica L. Beauv.). Four seed rates viz., 8,10,12, and 14 kg/ha and five levels of NPK fertilizers viz., N0P0K0, N10P8K5, N20P16K10, N30P24K15, and N40P32K20 were included in a split plot design with three replications. Dry matter accumulation pattern was determined by harvesting 10 plants randomly at 30, 60, 80, and 102 DAS (days after swing). The yield and yield contributing characters of foxtail millet were influenced by seed rates and NPK levels except tillers per plant and 1000-grain weight significantly. Generally its production rate was 0.86 t/ha when it was grown in char lands in sandy loam soils, the highest grain yield (1.62 t/ha) was produced by 10 kg seeds/ha, which was identical with 12 kg seeds/ha. In case of NPK levels, the treatment was N30P24K10. In case of interaction, the treatment combination 12 kg seeds/ha and N30P24K15 produced the highest grain yield (1.77 t/ha. In case of interaction, the treatment combination 12 kg seeds/ha and N,sub>30P24K15/ha gave the highest grain yield. DOI: http://dx.doi.org/10.3329/bjar.v38i4.19661 Bangladesh J. Agril. Res. 38(4): 689-704, December 2013

Characteristics of Dry Matter Accumulation and Effect of Fertilizer Application in Cassava

The field trials were conducted at two sites nearby the Tropical Center to investigate the influence of variety and fertilization on dry matter formation and accumulation of cassava. Two varieties of newly developed SC5 and conventional SC205 were used with five fertilization treatments including NP (1.0:0.4:0), NK (1:0:1), PK (0:0.4:1.0), NPK (1.0:0.4:1.0) and CK (no fertilizer application). Results indicated that the dry matter accumulation patterns were similar for both varieties. From transplanting to early August, dry matter accumulation mainly allocated in above-ground parts. When tubes started rapidly growing from mid August, the allocation of dry matter accumulation was shifted from above-ground to underground parts, and there was a difference between two varieties in accumulating velocity and distributing proportion of biomass. SC5 had larger crown with many earlier developing branches and leaves compared with SC205, resulting in more biomass accumulation in above-ground parts, thus reducing harvesting index. For fertilizer application, N was the most significant factor to increase dry matter, following K and P. Combining application of NPK (1.0:0.4:1.0) significantly enhanced accumulating velocity of dry matter and tube yields of cassava. There were some difference between two varieties in dry matter accumulation depended on NPK fertilizer application, and probably related to their nutrient demands and root developing level.

Plant growth and phenolic compounds in the rhizosphere soil of wild oat (Avena fatua L.)

The objectives of this study were to determine the pattern of dry matter (DM) accumulation and the evolution of phenolic compounds in the rhizosphere soil from tillering to the ripe seed stages of wild oat (Avena fatua L.), a widespread annual grassy weed. Plants were grown under controlled conditions and harvested 13 times during the growing season. At each harvest, shoot and root DM and phenolic compounds in the rhizosphere soil were determined. The maximum DM production (12.6 g/plant) was recorded at 122 days after sowing (DAS; kernel hard stage). The increase in total aerial DM with age coincided with reductions in the leaf/stem and source/sink ratios, and an increase in the shoot/root ratio. HPLC analysis shows production of seven phenolic compounds in the rhizosphere soil of wild oat, in order of their decreasing levels: syringic acid, vanillin, 4-hydroxybenzoic acid, syringaldehyde, ferulic acid, p-cumaric acid and vanillic acid. The seasonal distribution for the total phenolic compounds showed two peaks of maximum concentrations, at the stem elongation stage (0.71 μg/kg; 82 DAS) and at the heading stage (0.70 μg/kg; 98 DAS). Thus, wild oat roots exude allelopathic compounds, and the levels of these phenolics in the rhizosphere soil vary according to plant maturity.

Impact of nitrogen concentration variability in sugar beet plant organs throughout the growing season on dry matter accumulation patterns

Nitrogen concentration (Nc) in leaves, in each stage of sugar beet development, is the major factor stimulating the accumulation of dry matter in leaves, which in turn affects the dry matter concentration in storage roots and, consequently, determines sugar beet yields. This thesis was verified based on the data obtained from a static field experiment conducted in 2001-2003, with eight fertilizing variants: without nitrogen (absolute control, PK), without one of the main nutrients (KN, PN), with a reduced amount of phosphorus and potassium (N + 25% PK, N + 50% PK) and the recommended amount of all basic nutrients (NPK, NP*K, P* – P in the form of PAPR). Nitrogen concentrations in leaves and storage roots of sugar beet tended to decline during the growing season, but the former tendency adhered to a linear-plateau model while the latter corresponded to an exponential one. This discrepancy, revealed in the second part of the season, can be considered as an indicator of a high yield of storage roots, especially in years favorable for sugar beet vegetation. The growth analysis allowed us to determine the time and the maximum rate of canopy and storage root growth during the season. Irrespective of the fertilizing variant, both organs of sugar beet reached the maximum rate of growth from 92 to 113 day after sowing (DAS). Plants grown under conditions of ample water and nutrient supply (2001) reached a three-fold higher rate of leaf growth than in dry years (2002, 2003). The storage root showed much smaller differences in the absolute rate of growth. However, the effect of fertilizing variants was stronger, especially from 92 DAS onwards. Trends of the relative growth rate for each of the two tested plant organs were very similar. The highest growth rate for both organs occurred in early stages of sugar beet development and then progressively declined. Nevertheless, only this growth parameter responded si-

Dry Matter Accumulation and Nutrient Uptake by Wheat (Triticum aestivum L.) under Poplar (Populus deltoides) Based Agroforestry System

Wheat (Triticum aestivum L.) being grown with association of boundary plantations of poplar (Populus deltoides M.) has to face competition for water and nutrients uptake. Field experiment was carried to study the dry matter accumulation pattern and nutrients uptake by wheat grown in association with boundary plantations of three- and four-year-old poplar plants under irrigated condition. Dry matter accumulation of wheat declined considerably due to presence of poplar tree line during all the growth stages as compared to pure crop. Maximum reduction in dry matter accumulation in wheat was observed near the tree line (0–3 m) under both three- as well as four-year-old plantation (21.1 and 17.8 per cent under three- and four-year-old trees, resp.) which tapered off beyond that, but synergetic effect caused by existence of trees increased dry matter significantly between 3–6 m distance and 6–9 m distance under both three- as well as four-year-old plantation. Similarly, minimum concentration of nutrients (nitrogen, phosphorus, and potassium) as well as their uptake in wheat plants was observed near the tree line (0–3 m) and increased subsequently with increase in distance from tree line.

The seasonal and inter-annual patterns of biomass accumulation and crude protein in kleingrass (Panicum coloratum) in the semiarid Pampean region of Argentina

C. M. Ferri. 2011. The seasonal and inter-annual patterns of biomass accumulation and crude protein in kleingrass (Panicum coloratum) in the semiarid Pampean region of Argentina. Cien. Inv. Agr. 38(2):191-198. Kleingrass (Panicum coloratum L. var. coloratum) is a perennial warm-season grass that begins its growing season later in the spring than does weeping lovegrass (Eragrostis curvula (Schrad.) Nees), which suggests that combining weeping lovegrass with kleingrass in a grazing sequence could increase livestock production. The objectives of this study were to determine the seasonal and inter-annual variation of the patterns of the accumulation of dry matter (DM) and the percentage of crude protein (CP) in P. coloratum, cv. Verde, in the semiarid Pampean region of Argentina. This study was performed during four growing seasons in a 3.0 ha pasture of kleingrass that was sown in the spring of 1996. The forage samples were gathered at biweekly intervals and were separated into leaf blade, stems (including sheaths and inflorescence) and senescent material. Finally, patterns of dry matter accumulation and the percentage of crude protein were evaluated in relationship to the thermal time accumulated from early October to late February. In comparison with the other growing seasons evaluated, the third growing season had less (P ≤ 0.01) accumulation of dry matter and a higher (P ≤ 0.01) proportion of green leaf blade and CP. Dry matter accumulation increased with increases in the thermal time. The CP percentage of the total biomass and of the plant parts declined as thermal time increased, and this coincided with a reduction in the proportion of green leaves and the CP percentage in each plant part. Management decisions depend on an accurate assessment of the change in sward structure and nutritive value during the growing season. The results of this study will allow selection of the appropriate grazing time and the management of sequential grazing of warm-season grasses.

Remobilization of Dry Matter and Nitrogen in Maize as Affected by Hybrid Maturity Class

The length of the growing cycle is one of the most important traits determining hybrid adaptability to the environment. The objective of this research was to compare in a field trial the pattern of dry matter and nitrogen accumulation and remobilization of four commercial maize hybrids belonging to FAO maturity group 400, 500, 600 and 700. The duration of the periods emergence-silking and silking-physiological maturity increased with the increase of hybrid maturity class. Silking occurred 6 days later in the latest maturing hybrid than in the earliest one, and physiological maturity 21 days later. Hybrids differed for biomass production at silking and at physiological maturity. At silking, plant dry weight and leaf area increased with hybrid maturity, owing to greater leaves and stalks. The lengthening of the period emergence-silking allowed a greater accumulation of assimilates in the plant, thus increasing the source of remobilization in the following period. The increase of the length of the period silking-maturity from hybrid 400 to hybrid 700 brought to an increase of dry matter accumulation coupled to a reduction of dry matter remobilization. Increases in hybrid maturity class resulted also in an increase of post-silking N uptake and N remobilization from vegetative plant parts. Thus, the longer period silking-maturity was associated with an increased photosynthetic activity of the plant, which hampered the rate of leaf senescence and deterred the mobilization of reserve carbohydrates for grain filling. Conversely, the longer was the hybrid cycle, the greater was the quantity of both N uptake from soil and remobilized N from vegetative plant parts.