Estimation of water quality dynamics under long-term anoxic state in organically polluted reservoir by field observations and improved ecosystem model

In closed water bodies with significant organic pollution, anoxification due to thermal stratification leads to the elution of nitrogen and phosphorus from the bottom sediment and the generation of sulfide, resulting in further degradation of the water environment. This study focuses on the water quality dynamics in an organically polluted reservoir exhibiting long-term anoxification using two approaches: (1) field observations of seasonal changes in vertical profiles of dissolved oxygen, nitrogen, phosphorus, and sulfide and (2) construction of a water quality prediction model based on an ecosystem model incorporated with anaerobic biochemical processes. Iron and sulfate reduction occurred simultaneously because nitrate–nitrogen was reduced by denitrifying bacteria after the anoxification, and iron reduction became the main factor of the increase in ammonium–nitrogen and phosphate–phosphorus. The redox state of the bottom sediment surface, when anoxification began to occur, greatly affected the water quality dynamics caused by gradual reductive reactions under anaerobic conditions. Furthermore, the calculation accuracy of ammonium–nitrogen, phosphate–phosphorus, and sulfide was highly improved by modifying the conventional model based on the field observations. The characteristics of water quality under anaerobic conditions were sufficiently reflected in the upgraded ecosystem model. The proposed water quality prediction model could be used to quantitatively estimate the water environment dynamics in organically polluted water bodies. The model could be developed further in the future to solve the problems caused by long-term anoxification.     

Effect of organic matter input on the water balance and yield of millet under tropical dryland condition

In Senegal, rainfed millet production is influenced by the combination of scarce and unpredictable rains and falling soil fertility. In order to analyse the interaction between the water and fertility factors under conditions of low rainfall, the water use by a millet crop (Pennisetum glaucum L.) was studied under different organic matter input situations. Water balance was evaluated using a model and in situ soil moisture measurements.Application of manure raised the crop water requirements without substantially increasing the water supply of the soil. At the end of the crop cycle, the soil dried faster where manure was applied than without manure. The consequences of this on growth and production were studied: changes in the pattern of evolution of the soil water content induced by manuring limited the depth of root penetration, and promoted post-flowering water constraint that can cancel the positive effect of manure on growth and production. As a result, the use of manure increases the risks taken by the farmer and should therefore be taken into consideration for the analysis of existing cropping systems or the definition of possible new ones.     

The influence of three different farming systems on organic matter in the soils

Organic matter is one of the major factors influencing the productivity of the soil and the quality of food and fodder plants grown in the soil. It contributes to nutrient availability through decomposition and by acting as a chelating agent. The cation exchange capacity of a soil is dependent largely on the organic matter and it assists in the development of a good soil structure.Although many data are available from field trials very little is known of the influence of farming systems on organic matter. In this paper data are presented on the organic matter found in the fields of an experimental farm at the end of a thirty year period during which time three distinct sub-farms had followed three different farming systems. The crop rotations and fertiliser treatments for the different sections are detailed.The organic matter of the fields in rotation in the stockbearing sections were significantly higher than that of the stockless section (P<0.1) and there was some indication of a difference between the mean value for the permanent pasture in the two stockbearing sections (5.0

Zusammenfassung Organische Substanz ist eine der Hauptfaktoren, die die Produktivität der Böden und die Qualität der auf den Böden wachsenden Nahrungs- und Futterpflanzen beeinflußen. Durch Zersetzung und durch Funktion als Chelat-Agens trägt organische Substanz zur Verfügbarkeit der Nährstoffe bei. Die Austauschkapazität für Kationen eines Bodens hängt weitgehend von der organischen Substanz ab, außerdem trägt sie zur Bildung einer guten Bodenstruktur bei.Obwohl über Feldversuche sehr viele Angaben vorliegen, ist über den Einfluß des Bewirtschaftungssystems auf die organische Substanz im Boden sehr wenig bekannt. In dieser Arbeit werden Ergebnisse veröffentlicht über den Gehalt an organischer Substanz auf den Feldern einer Versuchsfarm am Ende einer 30jährigen Periode, während der drei getrennte Zweigbetriebe drei verschiedene Bewirtschaftungssysteme durchführten. Fruchtwechsel und Düngungsmaßnahmen auf den verschiedenen Feldschlägen werden aufgeführt.Diejenigen Felder, die im Laufe des Fruchtswechsels auch als Viehweiden genutzt wurden, wiesen einen höheren Gehalt an organischer Substanz (p<0,1) auf, als die Felder anderweitiger Nutzung. Es gibt Anzeichen dafür, daß zwischen den Mittelwerten der Dauerweiden auf den beiden Sektionen mit Viehhaltung Unterschiede bestehen (5,0     

Effects of fertilizer,variety and location on barley production under rainfed conditions in Northern Syria 2. Soil water dynamics and crop water use

The effects of fertilizer and location on the water use of two contrasting varieties of barley were studied in Northern Syria using a neutron probe. The observed patterns of soil moisture dynamics and crop water use were typical of those previously observed in Mediterranean-type environments. Moisture supply, as reflected by rainfall, was the principal factor affecting total water use, but both the application of fertilizer (N and P) and varietal differences also resulted in increased water use, particularly at the wetter location. There were no differences in the water-use efficiency between the two varieties, but the application of fertilizer resulted in large increases of water-use efficiency at both locations. Separation of crop evapotranspiration into crop transpiration and soil evaporation indicated that increased water-use efficiency was partially due to increased transpiration efficiency but was largely due to a reduction in soil evaporative loss, through greater soil shading by the crop canopy, and increased crop transpiration. Examination of this dataset together with the patterns of root and shoot growth suggest that fertilizer and varietal effects on root growth are linked to patterns of water use, growth and yield formation in barley.     

Effects of the colour and thickness of polyethylene film on ensiling conditions and silage quality of chopped maize, as investigated under ambient conditions and in mini-silos

Abstract The influences of variations in thickness and colour of agricultural plastic film on silage preservation conditions and silage quality were investigated. Thirty cylindrical plastic containers (mini‐silos; 0·3 m³) were filled with chopped maize and covered with five different types of film (90 µm white, 150 µm transparent, 150 µm white, 150 µm black, 200 µm white). Four mini‐silos of each variant were placed in the open air, and two were housed and subjected to a test procedure. The maximum storage period of silages was 104 d. The surface temperature of the films was found to be strongly dependent on the type of sheet. The temperatures inside the mini‐silos directly under the film differed significantly, whereas this effect was not recorded in the centre of the mini‐silos. In all, the differences were quantitatively small. Results of the chemical analysis of silages did not reveal any significant influence of film type. This was also the case when restricting the analysis to the uppermost silage layer. These findings are discussed against the background of the relatively small temperature differences and likely effects on gas permeability. On the basis of the results presented, it is concluded that, under the conditions of the experiment, well‐preserved forage of high nutritive value can be produced with silo sheets of differing colour, as well as with those of reduced thickness. Adequate mechanical robustness has to be ensured, if there is a reduction in film thickness.     

Effect of the Lactiplantibacillus plantarum and Lentilactobacillus buchneri on corn and sorghum silage quality and sheep energy partition under tropical conditions

This study aimed to evaluate the silage quality, ingestive behaviour, and sheep energy partition fed corn and sorghum silages, with or without inoculation with Lactiplantibacillus plantarum and Lentilactobacillus buchneri. Whole plants of one dent corn hybrid (DCS), one flint corn hybrid (FCS), and one forage sorghum hybrid (SS) were ensiled with or without an inoculant containing L. plantarum and L. buchneri (4 × 10⁵ CFU g⁻¹), totalling six treatments (3 × 2 factorial scheme). The treatments were ensiled in metal drums with 200 L capacity. The lactic acid concentrations in the inoculated FCS and DCS were higher by 13.4% and 12.8%, respectively, than those in the non-inoculated plants. In contrast, the lactic acid concentration in the inoculated SS was 23.1% lower than that in the non-inoculated SS. Furthermore, there were differences in pH and acetic acid concentrations only in SS, which were 2.3% and 45.2% higher, respectively, in inoculated silage than in non-inoculated silage. In inoculated DCS and SS, propionic acid concentrations were 1.7 times higher (for both silages), and 1-propanol was 3.7 and 1.8 times higher compared than those in non-inoculated silages. There was a main effect of the inoculant on 1,2-propanediol concentrations, which were 37.5% higher in inoculated silages than in non-inoculated silages. However, ingestive behaviour, heat and methane production, and silage net energy concentrations were not affected by inoculant use. Fermentative modifications caused by inoculation with L. plantarum and L. buchneri in whole plant corn or sorghum silage did not modify sheep energy partition.     

温光因子对稻米品质影响的研究进展

水稻灌浆期的温度和光照条件是影响稻米品质的重要环境因素。本文从稻米碾磨品质、外观品质、蒸煮食味品质和营养品质四个方面,综述了温光因子对稻米品质影响的最新研究进展,并以此为依据对优质稻米的生产提出了一些建议。     

Effects of partial root-zone drying on yield,tuber size and water use efficiency in potato under field conditions

Water resources are limited for irrigation worldwide; therefore, there is a need for water-saving irrigation practices to be explored. Partial root-zone drying (PRD) is a new water-saving irrigation strategy being tested in many crop species. Experiments were conducted in potato (Solanum tuberosum L. cv. Folva) under open field conditions in 2004 and under a mobile rainout shelter in 2005. Two subsurface irrigation treatments were studied: full irrigation (FI) receiving 100% of evaporative demands, 50.1 and 201 mm of irrigation water in the 2 years, to keep it close to field capacity; and PRD, which received 21.7 and 140 mm of irrigation in 2004 and 2005 respectively. Due to rain in 2004, the PRD treatment was imposed over a short period only during the late tuber filling and maturing stages. In 2005, the PRD treatment was imposed during the whole period of tuber filling and tuber maturation. The PRD treatment was shifted from one side to the other side of potato plants every 5–10 days. Especially in 2005 it was apparent that stomatal conductance was generally lower in the PRD than in the FI plants, whereas leaf water potential tended to be lower in only a few instances. During the treatment period, plants were harvested five times, and no significant difference was found between the treatments in leaf area index, top dry mass and tuber yield. At final harvest, tubers were graded based on size into four classes C₁–C₄, of which the yield of the important marketable class (C₂) was significantly higher (20%) in the PRD than in the FI treatment. Compared with FI, the PRD treatment saved 30% of irrigation water while maintaining tuber yield, leading to a 61% increase of irrigation water use efficiency. The limited data of 2004 support these results. In summary, PRD is a promising water-saving irrigation strategy for potato production in areas with limited water resources.     

Experimental study on the influence of percolation patterns on the removal of soluble elements in stratified alluvial-soil paddy fields for rice

The dynamics of substances in percolating water was investigated using paddy field models planted with rice and fertilized. Percolation patterns mimicking the plow layer and plow sole were set up in these models for closed system percolation. In one of these models, in which the groundwater level was kept high, the percolation pattern of the subsoil layer was set up as closed system percolation. In another model with a lower groundwater level, the percolation pattern of the portions above and below the groundwater level was set up as open and closed system percolation, respectively.The results show that the concentrations of nitrate nitrogen and nitrite nitrogen in percolating water were higher in the upper portion of the subsoil layer with open system percolation than in the plow layer and plow sole with closed system percolation, while these concentrations tended to be lower in the lower portion of the subsoil layer with closed system percolation than in the plow layer and plow sole. Iron and manganese concentrations in the subsoil layer were higher in the portion with closed system percolation than those in the portion with open system percolation. The concentrations of bases such as calcium tended to increase with the increase in iron concentrations in soil water.     

Root growth,soil water content and yield of barley under different tillage systems on two soils in semiarid conditions

An experiment was conducted on two soils in a semiarid area in the Spain’s Ebro valley. Soil A was a Fluventic Xerochrept of 120 cm depth and Soil B was a Lithic Xeric Torriorthent of 30 cm depth. Three tillage systems were compared in Soil A: subsoiler tillage, minimum tillage and no-tillage, and two (minimum tillage and no-tillage) in Soil B. The experiment was repeated for 5 years on Soil A and 3 years on Soil B. Root length density, volumetric water content and dry matter were measured at important developmental stages. Yield was determined at harvest. In Soil A, root length density and volumetric water content were significantly greater for no-tillage than for subsoiler or minimum tillage (up to 1.4 cm cm⁻³ and 5%, respectively), mainly in the upper part of the soil profile. At lower depths, differences as great as 0.8 cm cm⁻³ and 6% were also found. Mean yield (4 years) was similar between no-tillage (3608 kg ha⁻¹) and minimum tillage (3508 kg ha⁻¹), and significantly smaller for subsoiler tillage (3371 kg ha⁻¹). In Soil B, no differences were observed between tillage systems for volumetric water content. Significant interactions between tillage and year were found for root length density, dry matter and yield. Mean yield (3 years) was not significantly different for minimum tillage (1806 kg ha⁻¹) and no-tillage (1867 kg ha⁻¹). The results in Soil A showed that surface conditions are of major importance in the water content of the soil and determined the differences among tillage systems. No-tillage favoured greater and deeper water accumulation in the soil profile and greater root growth. This makes this system potentially better for years of low rainfall. In Soil B no tillage system proved to be better because of the low water-holding capacity of this soil (56 mm).     

Effects of different water management practices on the dry matter production process and characteristics in NERICAs

ABSTRACT

In this study, we aimed to clarify the effects of different water management strategies on dry matter production and yield performance of New Rice for Africa (NERICA) varieties. Dry matter production of NERICA 1 and NERICA 5 was compared with that of Yumenohatamochi, a Japanese upland variety, and Hinohikari, a Japanese lowland variety under three water regimes, i.e. continuously flooded, supplemental irrigation, and non-irrigation (rainfed). Total carbohydrate content in the panicles under different watering regimes was more closely related to post-heading photosynthates than pre-heading reserve assimilates. Dry matter production during ripening tended to decrease under low soil water conditions, whereas the dry matter translocated from the leaf and stem to the panicle tended to increase. Consequently, the distribution ratio of post-heading photosynthates in the total carbohydrate content declined in response to the reduction in available soil moisture. These results indicate that the total carbohydrate content vary depending on the soil water conditions. In NERICAs, dry matter production during ripening was lower than that in Japanese varieties, indicating that their dependence on pre-heading reserve assimilates was greater. In particular, post-heading photosynthate content of NERICA 1 was strongly affected by the variation in water management in comparison with that of other varieties. The decrease in crop growth rate during ripening in NERICA 1 can be mainly attributed to the lower post-heading photosynthate content. Thus, the ability of NERICA 1 to assimilate carbon after heading was considered to be potentially low, which has to be improved to achieve higher yield.     

Impact of long-term frozen storage on the dynamics of water and ice in wheat bread

Frozen storage of bread has a substantial impact on the dynamics of water and ice in the crumb and crust. In this study, the impact was characterized using wheat bread stored at −18 °C for a long term of ∼4 months. The frozen bread incurred a considerable loss of the crumb water that migrated out and formed ice crystals on the bread surface. Such a moisture decrease underwent more rapidly for the bread stored without intact crust, suggesting the specific role of crust during frozen storage. Moisture also redistributed significantly within the frozen crumb, resulting in an elevated crumb heterogeneity of freezable water. This redistribution of freezable water was accompanied by a progressive recrystallization of the crumb-borne ice crystals, which were measured to grow into bulk sizes using a modified calorimetric procedure for analyzing the crumb samples at their as-frozen states.     

Effect of N rate,timing and splitting and N type on bread-making quality in hard red spring wheat under rainfed Mediterranean conditions

Three different experiments were designed to study the effects of N fertilizer rate, timing and splitting, and the response to combined application of N and S fertilizer on the bread-making quality of hard red spring wheat (Triticum aestivum L.) over a 3-year period in Vertisols under rainfed Mediterranean conditions. The following parameters were analyzed: grain yield, test weight, grain protein content, gluten index and alveograph parameters (W: alveogram index; P: dough tenacity; L: dough extensibility; P/L: tenacity–extensibility ratio). The N rate experiment included rates of 0, 100, 150 and 200 kg N ha⁻¹ applied on four different sites. The experiment was designed as a randomized complete block with four blocks. For the experiment on N timing and splitting, a single rate of 150 kg N ha⁻¹ was used, different fractions being applied at sowing, tillering and stem elongation, at a single site; again, experimental design was a randomized complete block with four blocks. Finally, for the experiment on the response to combined application of N and S fertilizer, a single fertilizer dose of 150 kg N ha⁻¹ was applied in two forms (urea+ammonium nitrate and urea+ammonium nitrosulfate) with one leaf application at ear emergence (zero, 25 kg S ha⁻¹, 25 kg N ha⁻¹, $\text{25}\text{kg}\text{S}\text{ha}{}^{\mathrm{-1}}\text{+25}$ kg N ha⁻¹ and 50 kg N ha⁻¹), also at a single site, using a split-plot design with four replications. Year-on-year variation in rainfall led to marked variations in wheat yield, grain protein content and bread-making quality indices. A close correlation was observed between rainfall over the September–May period and both grain yield and grain protein content (optimum values for both being recorded in the rainfall range 500–550 mm) as well as the alveogram index. A negative correlation was observed between mean maximum temperatures in May and both test weight and alveogram index (W). N fertilizer rate had a more consistent effect on bread-making quality than on grain yield. The highest values for grain yield were recorded at an N rate of 100 kg ha⁻¹, while maximum grain protein content values were recorded at 150 kg ha⁻¹. Application of half or one-third of total fertilizer N at stem elongation improved grain yield and grain protein content with respect to applications at sowing alone or at both sowing and tillering. Increased N rates led to a considerable increase in W values and to a reduction in the P/L ratio, thus improving dough balance, with a negative effect on the gluten index. Leaf application of N at ear emergence only affected grain protein content and the W index. Soil or leaf application of S had no effect on protein quality indices. The response of grain yield and grain protein content to fertilizer N differed from that reported for temperate climates.     

Effects of water vapor pressure difference on leaf gas exchange in potato and sorghum at ambient and elevated carbon dioxide under field conditions

High leaf to air water vapor pressure differences often substantially reduce rates of assimilation of carbon dioxide, especially in C₃ species. Rising concentrations of carbon dioxide [CO₂] in the atmosphere could reduce the sensitivity of assimilation rate to partial stomatal closure caused by high vapor pressure difference by a variety of mechanisms. However, field data addressing this question are scarce. In this study, we examined day-to-day variation in midday gas exchange rates of upper canopy leaves of potato and sorghum grown at the current ambient [CO₂] and ambient+350 μmol mol⁻¹ [CO₂] in field plots. Stomatal conductance and assimilation rate were negatively correlated with vapor pressure difference across days. Assimilation rate was not less sensitive to vapor pressure difference at elevated than at ambient [CO₂] in either species. For both potato and sorghum short-term increases in vapor pressure difference for individual leaves produced significantly smaller responses of leaf gas exchange than did the day-to-day variation in vapor pressure difference, again with no reduced sensitivity at elevated [CO₂]. The smaller response of gas exchange to short-term manipulations of vapor pressure difference than to day-to-day variation may indicate that much of the response to high vapor pressure difference apparent in the day-to-day variation resulted from leaf water deficits caused by exposure of the whole canopy to high vapor pressure difference, rather than from direct effects of high water vapor pressure difference. The lack of a [CO₂] effect on the sensitivity of assimilation rate to vapor pressure difference, and the substantial sensitivity of assimilation rate to vapor pressure difference in the C₄ species both resulted from reductions in assimilation at a given internal [CO₂] at high vapor pressure difference. An implication of these results is that that high leaf to air water vapor pressure difference may continue to be a major limitation to assimilation rates in C₃ and C₄ crop species even at twice the current concentration of carbon dioxide in the atmosphere.     

Effect of type of underlay film on fermentation profile,nutritional quality and estimated loss of organic matter in the outer layer of whole‐plant maize ensiled in large bunker silos

Losses of organic matter in the outer layers of bunker silos covered with conventional polyethylene (PE) plastic can be substantial due to oxygen transmission through the plastic top‐covering film during the post‐ensiling storage period. The effect of two silo covering materials, oxygen barrier (OB) film (45 μm thickness) and clear PE film (50 μm thickness), as underlays to a white‐on‐black PE plastic top cover (120 μm thickness), was assessed in the outer layer of whole‐plant maize silage stored in three large bunker silos in the People's Republic of China. Samples of the crop at harvest and of silage from the upper 45 cm layer at 5 months post‐ensiling, prior to removal of silage for feed‐out, were analysed for DM, fermentation profile and chemical composition. Loss of OM was estimated from concentrations of ash in the crop at harvest and in the silage. Differences between underlay films in silage fermentation profile were small. Silage protected with OB underlay film had higher mean concentration of starch (p < .008) and higher mean NDF digestibility (p < .003) than silage under PE underlay film. Concentrations of ash were lower (p < .001) for silage covered with OB film than for PE film in all three trials. Mean estimated losses of OM were 170 g/kg for OB underlay film and 232 g/kg for PE underlay film (p < .001), and whole‐silo estimated net economic benefits to OB underlay film ranged from 0.17 to 0.74 US $ per tonne fresh crop ensiled.     

The weight of potatoes in water: Further studies on the relation between the dry matter and starch content

Summary The weight in water (m _u ) of 100 g air-free potatoes multiplied by the dry matter factor (K) equals the percentage dry matter (m _t ) in the tubers. The weight in water is unaffected by the water in the potatoes but is reduced by air in the intercellular spaces and must be corrected for this by a constantk. From the specific gravity of the dry matter the factorK is estimated as 2.50. From the weight in water and the percentage of dry matter estimated by oven-drying of 5.413 samples between 1937 and 1964.K is also estimated as 2.50. The amount of air in potatoes varies. In 1.911 samples examined between 1937 and 1948 air reducedM _u on average by 0.8g, therefore,m _t (m _u +0.8)·2.5 orm _t ·m _u 2.5–2.00., In 2,732 samples examined between 1952 and 1964 the reduction was 0.6 g therefore,m _t —(m _u —0.6) 2.5 orm _t ·m _u ·2.5+1.5. The percentage dry matter can be calculated more exactly from the weight in water of potatoes from which the air has been evacuated by immersing the tubers in water in a closed container and subjecting to vacuum (50–20 mm Hg) for about 30 minutes.

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Zusammenfassung Die Beziehung zwischen Unterwassergewicht (m _w ) und Trockensubstanzgehalt (m _t ) von 100 g Kartoffeln wurde untersucht. In den Jahren 1937 bis 1964 wurde bei 5413 Mustern zu 5 kg von verschiedenen Kartoffelsorten das folgende Verh?ltnis festgestellt:K−m _t /m _w −2,5 auf der Basis von zunehmendemm _w bei zunehmendemm _t (Tabelle 1). Das spezifische Gewicht (d) der Trockensubstanz wurde bestimmt auf Grund der Wasserverdr?ngung, und das Verh?ltnisd/(d−1) wird Trocken-substanzfaktor K genannt. Im Jahre 1952 wurde das mittlere spezifische Gewicht von 26 Mustern mit 1,6689 errechnet. Daraus kann geschlossen werden, dassK−m _t /m _w −1,6689/(1,6689-1)−2,5 ist. Dieser Wert für K stimmt mit der für die 5413 Munster erhaltenen Zahl überein. Wenn diese Bestimmung ohne Fehler ist, erhalten wir:m _t −m _w K. In der Regel jedoch wird die Bestimmung vonm _w einem systematischen Fehler unterliegen, allgemein ungef?hr gleichwertig dem Volumen von luftgefüllten Interzellularr?umen. Diese vergr?ssern das Volumen der Kartoffeln und dadurch auch deren Wasserverdr?ngung, jedoch ohne Erh?hung des Kartoffelgewichtes, so dassm _w reduziert wird. Der Umfang, durch den das Unterwassergewichtm _w reduziert wird, variiert stark von Muster zu Muster und macht so die Bestimmung vonm _w unsicher. Wenn man die Luft durch Vakuumbehandlung aus den Kartoffeln entfernt und dann die Interzellularr?ume sich mit Wasser füllen l?sst, wird der Wert vanm _w erh?ht undm _w K wird fast gleich gross wiem _t . Wird die Vakuumbehandlung unterlassen, so muss eine Konstantek zum _t hinzugez?hlt werden. Bei 1911 Mustern, die zwischen 1937 und 1948 untersucht wurden, hat man festgestellt, dass die Luftm _w im Mittel um 0,8 g herabsetzte, daher warm _t (m _w −0,8)−2,5 oderm _t m _w 2,5+2,00. Bei 2732 zwischen 1952 und 1964 geprüften Mustern betrug die Reduktion 0,6 g, alsom _t −(m _w +0,6)−2,5 oderm _t −m _w 2,5+1,50. Selbst wenn der Mittelwert für eine grosse Zahl von Mustern bestimmt wird, variiert der Wert vonk entsprechend der Sorte und den Wachstumbedingungen. Aus diesem Grunde sollte der Wertk mit gebührender Rücksicht auf die lokalen Bedingungen fixiert werden. Im Gegensatz zuk scheint es, als obK 2,50 mit einem hohen Grad an Genauigkeit, entsprechendd/(d−1)−K bestimmt worden sei. Durch Bestimmung vond bei 27 Kartoffeltrockensubstanzmustern im Jahre 1965 wurde festgestellt, dassd=1,6694 undK−2,494 ist. Wenn alle Interzellularr?ume mit Wasser gefüllt sind, wird der Trockensubstanzgehalt durch Multiplikation des Unterwassergewichtes der Knollen (m _w ) mit 2,50 errechnet. Anderseits gibt es keine Methode zur Bestimmung des St?rkegehaltes (m _s ) ausm _w . Das Verh?ltnis zwischenm _w undm _s muss durch direkte St?rkebestimmungen gefunden werden. In Tylstrup wurden 266 St?rkebestimmungen mittels derEwers-Methode (1908) vorgenommen. Die Ergebnisse zeigten, dass der St?rkegehalt in Prozent (m _s ) eventuell durchm _s −(m _w −2,39)–2,28 errechnet werden kann. Der 1948 bis 1951 ermittelte St?rkegehalt ist infolge Vorhandenseins von Pektin wahrscheinlich zu hoch. Wenn die Muster für die St?rkebestimmung durch Bleiacetat bei pH 8 gekl?rt werden, kann das Pektin beseitigt werden. Es scheint jedoch, dass zusammen mit und im Verh?ltnis zum Pektingehalt ausserdem etwas St?rke scheinbar verschwindet. Dies dürfte verhütet werden, wenn dem Muster HCl beigefügt wird, bis der pH ungef?hr 2 betr?gt, bevor das Bleiacetat dazugewird. Muster, die mit 0,116 N HCl fiitriert und ausgewaschen werden, ergeben nahezu gleiche Ergebnisse, ob Bleiacetat bei pH 2 oder 8 hinzugegeben wird. In Tylstrup wurden von 1962 bis 1964 an 165 Mustern St?rkebestimmungen vorgenommen. Diese Analysen zeigten, dassm _s =(m _w −2,42)−4,10 entspricht. Auf Grund der Unteruchungen in Tylstrup zwischen 1952 und 1964 wurde die Tabelle 4 vorbereitet, die erlaubt, den Trockensubstanz-und St?rkegehalt in Prozent vom Unterwassergewicht eines Kartoffelmusters zu ermitteln, und zwar in beiden F?llen, d.h. wenn die Luft aus den Knollen entfernt oder nicht entfernt worden ist.

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Résumé On a recherché la relation entre le poids sous eau (m _w ) et la teneur en matièrè sèche (m _t ) de 100 g de pommes de terre. Durant la période 1937–1964, sur 5413 échantillons de différentes variétés de pommes de terre, chaque échantillon pesant 5 kg, on a trouvé que cette relation était:K=m _t /m _w =2,5 sur la base d'une augmentationm _w avec une augmentation dem _t (Tableau 1). Le poids spécifique (d) de la matière sèche est déterminé sur la base du déplacement d'eau et la relationd/(d−1) désignele facteur K de la matière sèche. En 1952 le poids spécifique moyen de 26 échantillons a été trouvé être 1,6689. De deci on peut déduire queK=m _t /m _w −1,6689/(1,6689−1)=2,5. Cette valeur deK s'accorde avec le chiffre obtenu à partir de 5413 échantil-Si la détermination est faite sans erreur nous obtenons:m _t =m _w K. Cependant, la détermination dem _w sera, généralement, entachée d'une erreur systématique largement égale au volume des espaces intercellulaires remplis d'air. Ceux-ci accroissent le volume de pommes de terre et ainsi le déplacement d'eau, sans accro?tre le poids des pommes de terre etm _w sera diminué. L'importance de la réduction varie grandement d'un échantillon à l'autre, rendant de la sorte la détermination dem _w incertaine. En évacuant l'air des pommes de terre par traitement par le vide et permettant alors aux espaces intercellulaires de se remplir d'eau, la valeur dem _w augmente etm _w K devient plus étroitement égal àm _t . Si le traitement par le vide est omis, une constantek doit être ajoutée àm _t . Sur 1911 échantillons examinés entre 1937 et 1948 on a trouvé que l'air réduisaitm _w de 0,8 g en moyenne et, par conséquent,m _t −(m _w +0,8) =2,5 ou m _t −m _w =2,5+2,00. Pour 2732 échantillons examinés entre 1952 et 1964, la diminution était de 0,6 g, par conséquent,m _t −(m _w +0,6)=2,5 oum _t −m _w =2,5+1,5. Même si la valeur moyenne pour un grand nombre d'échantillons est déterminée, la valeur dek variera suivant à la fois la variété et les conditions de croissance. Pour cette raison, la valeurk devrait être fixée en égard aux conditions locales. Au contraire dek il semblerait queK=2,5 a été déterminé avec un degré élevé de sécurité suivantd/(d−1)−K. En déterminantd sur 27 échantillons de matière sèche de pommes de terre en 1965 on a trouvé qued=1,6695 etK=2,494. Si tous les espaces intercellulaires sont remplis d'eau, la teneur en matière sèche est déterminée en multipliant le poids sous eau des tubercules (m _w ) par 2,5. D'autre part, il n'existe aucune méthode pour déterminer la teneur en amidon (m _s ) à partir dem _w . La relation entrem _w etm _s doit être trouvée par des déterminations directes d'amidon. A Tylstrup, 266 déterminations d'amidon ont été faites par la méthodeEwers (1908). Les résultats montrent que le pourcentage d'amidon (m _s ) peut être déterminé parm _s =(m _w +2,39)−2,28. Le pourcentage d'amidon trouvé de 1948 à 1951 est probablement trop élevé en égard à la présence de pectine. Si les échantillons pour détermination de l'amidon sont clarifiés au moyen d'acétate de plomb au pH d'environ 8, la pectine peut être enlevée. Il se révèle cependant qu'apparemment de l'amidon dispara?t aussi en même temps et proportionellement à la teneur en pectine. Ceci peut être évité en ajoutant HCl à l'échantillon jusqu' à ce que le pH soit d'environ 2, avant d'ajouter l'acétate de plomb. Les échantillons filtrés et lavés avec 0,116 N HCl donneront des résultats presque identiques, soit que l'acétate de plomb soit ajouté au pH 2 ou 8. Les déterminations d'amidon ont été faites sur 165 échantillons à Tylstrup de 1962 à 1964. Les analyses montraient quem _s −(m _w +2,42)−4,10. Sur la base des recherches à Tylstrup entre 1952 et 1964 on a établi le Tableau 4 qui permet de déterminer le pourcentage de matière sèche et le pourcentage d'amidon à partir du poids sous eau d'un échantillon de pommes de terre, à la fois quand l'air est ou n'est pas enlevé des tubercules.

     

Effect of anaerobic digestion residue vs. livestock manure and inorganic fertilizer on the hygienic quality of silage and haylage in bales

An increased recycling of nutrients from organic waste to support feed and food production is important for achieving sustainability. However, organic waste may contain undesired microorganisms that may increase the risk of impaired hygienic quality of feeds when used in forage‐cropping systems. This study aimed to investigate how the hygienic quality of silage and haylage was affected after fertilization of grassland with organic fertilizers [anaerobic digestion residue (ADR) pasteurized before spreading, or liquid cattle manure] compared with inorganic NPK fertilization. The experiment was performed on the same grass ley for 2 years, with fertilization carried out before each harvest (year 1, two harvests; year 2, one harvest). The crop was conserved as silage (300 g DM kg^?1) and haylage (500 g DM kg^?1) in bales (ca 40–55 kg) stored for 1, 5 or 10 months before opening, including effects of storage time and conservation method (silage or haylage) on hygienic quality. Results showed that ADR‐treated crops did not produce silage or haylage with higher microbial counts in comparison with manure‐treated crops on any occasion. The fermentation pattern in silage and haylage from ADR‐treated crops was similar to the pattern in manure‐treated crops. The use of inorganic fertilizer sometimes produced lower pH and higher content of lactic acid in silage, compared with using organic fertilizers. In conclusion, ADR could be used as an organic fertilizer for forage crops without increased risk of impaired hygienic quality compared with using liquid manure or inorganic NPK fertilizers.     

Productivity and residual benefits of grain legumes to sorghum under semi-arid conditions in south-western Zimbabwe: Unravelling the effects of water and nitrogen using a simulation model

The APSIM model was used to assess the impact of legumes on sorghum grown in rotation in a nutrient-limited system under dry conditions in south-western Zimbabwe. An experiment was conducted at Lucydale, Matopos Research Station, between 2002 and 2005. The model was used to simulate soil and plant responses in the experiment. Sequences of cowpea (Vigna unguiculata), pigeonpea (Cajanus cajan), groundnut (Arachis hypogaea) and sorghum (Sorghum bicolor) were used in the rotations. Legumes accumulated up to 130 kg of N ha⁻¹ which was potentially available for uptake by sorghum in the following season. The APSIM model predicted total biomass, grain and N yields of the legume phase within the experimental error and performed well in predicting sorghum yield and N supplied in the rotation after cowpea and groundnut. The model generally under-predicted sorghum total biomass and grain yield after pigeonpea. Observed patterns of crop water use, evaporative losses during the dry season and re-charge of soil profile at the start of the rainy season were generally well predicted by the model. An assessment of output on sorghum N and water stresses in the rotation indicated that the legume–cereal rotation is more driven by soil nitrogen availability than water availability even under semi-arid conditions. Further legume–cereal rotation analysis using the model will assist in the understanding of other processes in the rotations in dry environments.     

栽培密度对高油大豆籽粒产量及品质影响初探

栽培密度对大豆产量和品质性状影响的研究结果表明，生物重和籽粒重在不同密度间均存在在显著差异，蛋白质和脂肪含量在不同的栽培密度下有一定程度的差异，但未达到显著水平。籽粒重随密度（在供试的密度范围内）的增加而提高。在14．5万株／hm^2栽培时，生物重达最高，籽粒重和脂肪含量在15．75万株／hm^2时达最高，蛋白质含量在12．25万株／hm^2栽培时达最高。