Quality Of Crop Residues Research Articles

Interactive effects of crop residue quality and nitrogen fertilization on soil organic carbon priming in agricultural soils

Soil organic carbon (SOC) priming affects C sequestration in soils, the intensity of which differs depending on residue quality. N fertilization could also alter SOC priming. However, the interaction of crop residue quality and N fertilization on the SOC priming is still not clear. To address this gap in knowledge, we conducted this study. We undertook a 110-day laboratory incubation experiment to evaluate the SOC priming and sequestration induced by maize shoot and root residues with and without the application of mineral fertilizer-N in two types of agricultural soils (Andisol and Entisol). Application rates of maize residue and N were 3 g C kg−1 soil and 60 mg N kg−1 soil, respectively. 13C-labeled maize residue allowed quantifying residue decomposition and calculating SOC priming and sequestration. After 110 days of incubation, the cumulative intensity of priming effect was higher for root residue than shoot residue. Addition of N results in contrasting effects on the priming effect induced by root and shoot residue in both types of soils; with root residue, it reduced the intensity of priming effect and resulted in a higher net C sequestration because of reduced N mining, whereas it had little effect with shoot residue, where co-metabolism is the likely explanation for the positive priming effect. Crop residue quality and N fertilization can interactively affect the SOC priming. N fertilization is beneficial for soil C sequestration when soil is treated with low-quality crop residue (e.g., root residue) because of lowering of the intensity of priming effect and crop residue decomposition.

Robustness of visible near‐infrared and mid‐infrared spectroscopic models to changes in the quantity and quality of crop residues in soil

AbstractThe robustness of soil organic carbon (SOC) and total nitrogen (TN) content prediction accuracy by visible near‐infrared spectroscopy (visNIRS) and mid‐infrared spectroscopy (MIRS) models after a change in the quantity or quality of crop residues requires investigation. Arable soils (0–20 cm) from 20 locations across Germany were collected, and 0, 2, 4, or 8 g C kg soil−1 of wheat straw (C/N ratio, 54) or clover (C/N ratio, 13) were added. Before and after a 56‐d incubation, dried and ground samples were measured for SOC and TN content and by visNIRS and MIRS. The complete dataset (n = 280) was subdivided into calibration and validation datasets to test the robustness of partial least squares regression models to changes in crop residue quantity and quality in soil. Noise‐reducing data pretreatments included region selection, moving averages, resampling every second data point, and the Savitzky‐Golay algorithm. The MIRS estimates for SOC (7.4–33 g kg−1) had lower root mean squared error of validation (RMSEV = 0.9–2.9 g kg−1) compared with visNIRS (RMSEV = 1.6–7.1 g kg−1). Total N estimates (0.7–2.8 g kg−1) were more comparable for MIRS (RMSEV = 0.1–0.3 g kg−1) and visNIRS (RMSEV = 0.1–1.0 g kg−1). Loadings of partial least squares regression components suggested the predictive mechanisms for SOC and TN were more similar for visNIRS than for MIRS. Differing crop residue quantity or quality in calibration versus validation resulted in biased SOC and TN estimates by visNIRS and MIRS models. However, calibration with a global residue model containing all soils and crop residue quantities and qualities lowered RMSEV for SOC and TN prediction with visNIRS and MIRS, demonstrating the usefulness of this approach.

How the mass and quality of wheat and vetch mulches affect drivers of soil N2O emissions

Crop residue affects nitrous oxide (N2O) emissions in no-tillage systems, but the magnitude of the emissions depends on soil drivers that are directly influenced by crop residue quality and quantity. We conducted a one-year study to investigate how mulch chemical characteristics and mass affect N2O emissions during their decomposition in the field under subtropical conditions. The mulch treatments consisted of vetch and wheat crop residues applied to the soil at quantities of 0, 3, 6 and 9 Mg ha−1 dry matter. We followed the kinetics of mulch carbon (C) and nitrogen (N), soil temperature, moisture and inorganic N, the denitrification end-product ratio [N2O/(N2O + N2)] at days 15 and 30, and N2O and carbon dioxide (CO2) emissions with a static chamber method. Mulch decomposition and C and N dynamics were very rapid for vetch and much more gradual for wheat, reflecting the differences in their initial chemical compositions, but for both residues, the initial mulch mass had no effect on the decomposition rate. The presence of mulches increased soil moisture in the 0–10 cm soil layer, with the results for water-filled pore space by treatment as 0 = 3 < 6 = 9 Mg ha−1. Vetch also significantly increased the inorganic N content in the soil, unlike wheat, which caused net N immobilization. The daily N2O fluxes were strongly and positively correlated with CO2 fluxes (r = 0.83). The highest N2O fluxes were observed in the first 60 days with the vetch residues, and the results increased by treatment as 0 < 3 < 6 = 9 Mg ha−1; for wheat, the mean N2O emitted was 50% lower than that for vetch and was not affected by mulch mass. Although the cumulative N2O emitted was higher in vetch than in wheat, the N2O emission factor was higher for the wheat than for the vetch residues (EF = 4.64% vs 1.75% of N applied). We conclude that while mulch mass and quality strongly influenced soil drivers of N2O emissions, not only the N input but also the nature of residue C and the residue location must be taken into account to understand and predict N2O emissions associated to crop residue management.

Improving the quality of crop residues by the reduction of ash content and inorganic constituents

Improving the quality of crop residues by the reduction of ash content and inorganic constituents

Improving the Quality of Crop Residues by the Reduction of Ash Content and Inorganic Constituents

In this study, the mechanical size fractionation technique and the water leaching technique were applied in sequence to reduce the ash content of crop residues to target value of 6% db (dry basis) following the applicable standard. Results showed that the finest fraction of ground crop residues (&lt; 0.25 mm) had much higher ash content than the coarser fractions, thus demonstrating that size fractionation can reduce the need for leaching as ash removal technique, and it was most effective for corn stover. For a water-to-biomass ratio (w/w) of 30, the final ash contents of the biomass materials involved in all experimental treatments were effectively reduced to below the target value. Canola straw had the highest ash removal efficiency and element removal efficiency as compared to wheat straw and corn stover. Even though the leaching condition (12 h, 25 °C) was adequate for effective ash reduction, SiO2 removal efficiency could be significantly improved when the leaching temperature was raised from 25 °C to 45 °C. A preliminary cost analysis indicated that biomass pretreatment by mechanical size fraction followed by water leaching as needed would lead to a 30% increase in the total production cost (TPC) of agro-pellets, and this is significantly lower than the increase in TPC by 66% if the pretreatment is done by water leaching only of the ground crop residues.

How diversity of crop residues in long-term no-tillage systems affect chemical and microbiological soil properties

Integrated systems of agriculture lead to better food and environmental quality, but these systems are complex and should be evaluated in long-term experiments. The objective of this study is to evaluate long-term NT systems with different histories, management and different quantity and quality of plant residues on chemical and microbiological soil properties. The NT systems are located in three experimental fields of Embrapa Cerrados, in the Cerrado region, with 26, 21 and 12 years of establishment. The NT systems were characterized for soil chemical and microbiological properties and for quantity and quality of crop residues. Soil properties studied were basal respiration (BR), microbial biomass carbon (MBC), total organic carbon (TOC), total nitrogen (TN) and microbial quotient (qMIC) in three depths from 0–30 cm layer. The systems with annual succession of soybean with maize intercropped with U. brizantha grazed or not in the off-season increased the quantity of crop residues (around 10.70 ton ha−1) and contributed more to the quality of the vegetal residues, in addition to increasing MBC (up to 716 mg kg-1 soil), TN (between 4 and 5 g kg-1 soil), TOC (35 to 40 g kg-1 soil) and qMIC (up to 1.83%), which indicates that this system promoted improvement in the quality of chemical and biological soil properties and contributed to carbon accumulation in the soil over a period of 26 years.

Evaluate the effect of harvest date on cover crop dry matter production and residue quality

Evaluate the effect of harvest date on cover crop dry matter production and residue quality

Microbial association with the dynamics of particulate organic carbon in response to the amendment of elevated CO2-derived wheat residue into a Mollisol

As the chemical quality of crop residue is likely to be affected by elevated CO2 (eCO2), residue amendments may influence soil organic carbon (SOC) sequestration. However, in Mollisols, the dynamics of the SOC fractions in response to amendment with wheat residue produced under eCO2 and the corresponding microbial community composition remain unknown. Such investigation is essential to residue management, which affects the soil quality and productivity of future farming systems. To narrow this knowledge gap, 13C–labeled shoot and root residue derived from ambient CO2 (aCO2) or eCO2 were amended into Mollisols and incubated for 200days. The soil was sampled during the incubation period to determine the residue-C retained in the three SOC fractions, i.e., coarse intra-aggregate particulate organic C (coarse iPOC), fine iPOC and mineral-associated organic C (MOC). The soil bacterial community was assessed using a MiSeq sequencing instrument. The results showed that the increase in SOC concentrations attributable to the application of the wheat residue primarily occurred in the coarse iPOC fraction. Compared with the aCO2-derived shoot residue, the amendment of eCO2-derived shoot residue resulted in greater SOC concentrations, whereas no significant differences (P>0.05) were observed between the aCO2- and eCO2-derived roots. Principal coordinates analysis (PCoA) showed that the residue amendment significantly (P≤0.05) altered the bacterial community composition compared with the non-residue amendment. Additionally, the bacterial community in the aCO2-derived shoot treatment differed from those in the other residue treatments until day 200 of the incubation period. The eCO2-derived shoot treatment significantly increased (P≤0.05) the relative abundances of the genera Acidobacteriaceae_(Subgroup_1)_uncultured, Bryobacter, Candidatus_Solibacter, Gemmatimonas and Nitrosomonadaceae_uncultured, whereas the opposite trend was observed in Nonomuraea, Actinomadura, Streptomyces and Arthrobacter (P≤0.05). These results imply that the response of the microbial community to the eCO2-derived shoot treatment is associated with its contribution to the POC fractions.

Soil nitrogen dynamics under different quality and application methods of crop residues in maize croplands with contrasting soil textures in Tanzania

ABSTRACTSoil nitrogen (N) dynamics in croplands need to be improved for the increase of food production in sub-Saharan Africa. Our objective was to investigate the crop residue management in terms of quality and application method to improve soil N dynamics during the period of crop growth in maize croplands with special reference to soil textures in dry tropical agroecosystems. Field experiments were conducted during the rainy seasons of 2012 and 2013 at clayey and sandy sites in Tanzania. Five treatment plots were established: plots with no residue applied (Ctrl plot), chemical fertilizer applied (F plot), maize residue (high C:N ratio = 60) incorporated (M-In plot) or mulched (M-On plot), and cowpea residue (low C:N ratio = 21) incorporated (P-In plot). In each plot, we regularly collected surface soil and crop samples and measured inorganic N (NO3−–N and NH4+–N), the soil respiration rate, and crop N uptake. Rainfall and soil moisture content were also continuously monitored. Our results showed that cowpea residue with high biodegradability caused prompt increases in the soil respiration rate and soil inorganic N because decomposition of the applied residue occurred within ca. 2 weeks after the application at both the clayey and sandy sites. It resulted in high N use efficiency in the early growing period and 18–73% higher total crop N uptake than that in the maize residue plots at both sites. The application methods (incorporation and mulching) showed no significant difference in soil N dynamics and crop yield, although higher soil respiration was observed in the M-In plot than the M-On plot at the clayey site. However, at the sandy site, mulching of maize residue resulted in the increased soil inorganic N content in the M-On plot by 18–26% compared with that in the M-In plot during the cropping season because of the higher soil moisture content. Consequently, crop N uptake in the mulching plot resulted in 26–59% higher than that in the incorporation plot.

Soil Carbon Fractions in Response to Long‐Term Crop Rotations in the Loess Plateau of China

Core Ideas Long‐term (30 yr) diversified crop rotations had a positive impact on soil C fractions. Carbon fractions increased with increased rotation length. Diversified rotations enhanced soil C sequestration and microbial biomass and activity. Diversified crop rotations may enhance C fractions and soil quality by affecting the quality and quantity of crop residue returned to the soil compared with monocropping and fallow. We evaluated the effect of 30‐yr‐old diversified crop rotations on soil C fractions at 0‐ to 15‐, 15‐ to 30‐, and 0‐ to 30‐cm depths in the Loess Plateau of China. Crop rotations were continuous winter wheat (Triticum aestivum L.) (W); 3‐yr rotations of corn (Zea mays L.)–winter wheat–winter wheat–millet (Eleusine coracana L.) (CWWM), pea (Pisum sativum L.)–winter wheat–winter wheat–millet (PWWM), and sainfoin (Onobrychis viciifolia Scop.)–winter wheat–winter wheat–sainfoin (SWWS); 4‐yr rotation of pea–winter wheat–winter wheat–corn (PWWC); and 8‐yr rotation of alfalfa (Medicago sativa L.) (4 yr)–potato (Solanum tuberosum L.) (1 yr)–winter wheat (3 yr) (A4PoW3). A fallow (F) treatment was also included for comparison. Carbon fractions were soil organic C (SOC), particulate organic C (POC), potential C mineralization (PCM), and microbial biomass C (MBC). At all depths, SOC and POC were greater in A4PoW3 than F, W, and PWWC. The PCM and MBC were greater with SWWS than most other crops rotations. Soil C fractions increased linearly with increased belowground crop residue returned to the soil. Both SOC and POC increased linearly with increased rotation length. All C fractions were also correlated with mean annualized crop grain yield. Diversified crop rotations with increased belowground residue production enhanced soil C sequestration and microbial biomass and activity as well as crop yield compared with monocropping.

Microbial decomposition of soil organic matter is mediated by quality and quantity of crop residues: mechanisms and thresholds

Crop residue quality and quantity have contrasting effects on soil organic matter (SOM) decomposition, but the mechanisms explaining such priming effect (PE) are still elusive. To reveal the role of residue quality and quantity in SOM priming, we applied two rates (5.4–10.8 g kg−1) of 13C-labeled wheat residues (separately: leaves, stems, roots) to soil and incubated for 120 days. To distinguish PE mechanisms, labeled C was traced in CO2 efflux and in microbial biomass and enzyme activities (involved in C, N, and P cycles) were measured during the incubation period. Regardless of residue type, PE intensity declined with increasing C additions. Roots were least mineralized but caused up to 60% higher PE compared to leaves or stems. During intensive residue mineralization (first 2–3 weeks), the low or negative PE resulted from pool substitution. Thereafter (15–60 days), a large decline in microbial biomass along with increased enzyme activity suggested that microbial necromass served as SOM primer. Finally, incorporation of SOM-derived C into remaining microbial biomass corresponded to increased enzyme activity, which is indicative of SOM cometabolism. Both PE and enzyme activities were primarily correlated with residue-metabolizing soil microorganisms. A unifying model demonstrated that PE was a function of residue mineralization, with thresholds for strong PE increase of up to 20% root, 44% stem, and 51% leaf mineralization. Thus, root mineralization has the lowest threshold for a strong PE increase. Our study emphasizes the role of residue-feeding microorganisms as active players in the PE, which are mediated by quality and quantity of crop residue additions.

Crop residue quality and soil type influence the priming effect but not the fate of crop residue C

Crop residues and soil types play an important role in soil C and N storage. The objectives of this study were to quantify the effects of crop residue quality and interactions with soil type on soil C and N, in the short- and medium-term, and to determine the responses related to the priming effect (PE). Residues of vetch (Vicia sativa L.), pea (Pisum sativum L.) and wheat (Triticum aestivum L.) crops with different chemical compositions and labelled with 13C and 15N were left to decompose on the surface of either a sandy-loam soil or a clay soil incubated under laboratory conditions at 25 °C for 360 days. We measured the total CO2-C and CO2-13C emitted during decomposition, the soil mineral N content and the amounts of 13C and 15N remaining in both the surface residue particles and the bulk soil. Over the short-term, the vetch residues decomposed faster than those of wheat and pea on the soil surface due to their more favourable chemical composition for biodegradation; after one year, however, this difference disappeared. We observed extra soil C mineralization in all cases, i.e., the PE was positive for all treatments and was directly related to the water-soluble (vetch > pea > wheat) and soil C contents (clay soil > sandy-loam soil). Conversely, the fate of the added 15N and net N mineralization differed considerably between the three residues and was strongly related to the initial N content of the residue. Crop residue quality and soil type affected the soil PE and soil C balance but not the fate of crop residue-C after one year. Net soil N mineralization was observed in all crop residues, with large early differences (vetch > pea > wheat), which were maintained on a medium-term basis. Our results emphasize the need to jointly consider C and N dynamics as well as short- and medium-term effects to manage agricultural and environmental services provided by the recycling of crop residues to agricultural soils.

Sowing methods and varying seed rates of cowpea on production potentialof sorghum, sudan grass hybrid and cowpea: A review

Forage requirement of livestock is generally met through low quantity and quality of crop residues often not enough for maintenance of animal health and productivity in India. Cereal-legume intercropping has been recognized as a beneficial crop production system for higher fodder production per unit area per unit time, especially, under rainfed conditions. Sorghum sudan grass hybrid and cowpea are some of the potential fodder crops which can provide good nutrition to livestock with higher forage yields and improve the fertility status of soil when grown in association. This paper reviews all the literature on various aspects of intercropping of cereals and legumes, mainly sorghum and cowpea, for better understanding and future strategies for improved production as well as quality of fodder.

ORGANIC MATTER PRODUCTION AND CHEMICAL COMPOSITION OF COVER CROPS FERTILIZED WITH NPK

SUMMARYThe crop rotation is a practice to protect and improve the soil properties and an alternative to improve the quality of crop residues is the application of fertilizers at the planting of cover crops. Thus, we evaluated the effect of fertilization with nitrogen, phosphorus and potassium (NPK) on organic matter production and chemical composition of cover crops succeeding the corn crop. The treatments consisted of the cultivation of Avena sativa L., Lupinus albus L., Pennisetum glaucum L., Raphanus sativus L. and Sorghum bicolor L. with (200 kg ha−1 of NPK [08-28-16] applied by broadcast seeding) and without fertilization at planting. Organic matter production by all cover crops, as well as concentrations of neutral detergent fibre (NDF) in shoots and roots of A. sativa L. and R. sativus L. were higher when they were fertilized. L. albus L. showed higher NDF and acid detergent fibre (ADF) contents than the other cover crops, with and without fertilization. Nitrogen concentration increased, but the carbon/nitrogen ratio (C/N) in the shoots of L. albus L., R. sativus L. and S. bicolor L. decreased when fertilization was applied. The use of N by the A. sativa L. and P. glaucum L. and of P and K by S. bicolor L. was 16, 54, 82 and 20% more efficient, respectively, when fertilization was applied. The A. sativa L., P. glaucum L. and R. sativus L. showed higher NDF/N, ADF/N and hemicellulose/N ratios in the fertilized treatment. Although the results obtained in this study are highly satisfactory, more research should be conducted to evaluate the decomposition of crop residues from cover crops fertilized with NPK, and the effects of this strategy on corn crops in succession.

For how long does the quality and quantity of residues in the soil affect the carbon compartments and CO2-C emissions?

Purpose The mineralization/immobilization of nutrients from the crop residues is correlated with the quality of the plant material and carbon compartments in the recalcitrant and labile soil fractions. The objective of this study was to correlate the quality and quantity of crop residues incubated in the soil with carbon compartments and CO2-C emission, using multivariate analysis.

The dynamics of soil micro-food web structure and functions vary according to litter quality

Anthropogenic pressures on agricultural soils are known to alter the properties of soil food webs, which may affect ecosystem functions and the capacity to deliver services. Cropping systems fuel belowground biota by supplying litter, but litter quality varies from year to year. In this study, we hypothesized that (i) the structure and function of the soil biota may respond strongly to the quality of crop residue, and (ii) this response may vary with the complexity of the food web. To test this hypothesis, a 3-month incubation experiment was performed using soil columns filled with a silty loam agricultural soil (Estrées-Mons, Northern France), and plant litter was incorporated into the 0–5-cm layer. The quality of the litter was modulated by using either high quality (maize leaves) or low quality materials (maize roots), and two levels of biotic complexity were tested by introducing or not introducing an ecosystem engineer (Lumbricus terrestris, anecic earthworm) into the columns. We then investigated litter decomposition and enzymatic activities, as well as the biomass and diversity of the bacterial, fungal and nematode communities. The C mineralization and enzymatic profiles varied according to litter quality, and the most obvious differences were observed in the hydrolytic enzymes and phenol oxidase. Micro-food web interactions and structure were mainly impacted by litter type and the time since litter incorporation, and as expected, we observed a temporal succession of cellulolytic organisms followed by lignolytic organisms. This progression was mirrored by the nematode community; the ratio of fungal feeders/bacterial feeders increased between 35 and 91 days. Initial litter quality primarily impacted bacterial and fungal community structure, and the development of the bacterial channel was greater with the addition of leaf litter. This was related to an increase in specific, favored phyla, Bacteroidetes and Proteobacteria, whereas Actinobacteria increased more with the addition of root litter. However, we could not statistically link the changes in the structure of the microbial communities over time with those in enzyme activity, which led us to assume that other factors, such as top-down regulation, are more important than microbial community structure in the determination of the enzyme secretions in the soil. Finally, the addition of earthworms did not significantly impact litter decomposition and had a low impact on micro-food web structure and interactions. However, the presence of L. terrestris did modify the enzymatic secretions, probably through its endemic microbial population, as well as the stimulation of microbial activity through predation.

Effect of Varying the Crop Residue, Cultivar and Physical form on Intake and Nutrient Utilization in Deccani Sheep Fed Complete Diets

Four crop residue based complete diets (60R: 40C) with Andhra hybrid and Telangana sorghum stover, paddy straw and sweet sorghum bagasse with leaf residue (SSBLR) as sole roughage were formulated and processed into either mash or block form to study the effect of crop residue, cultivar and physical form on intake, nutrient utilization and N balance in growing Deccani ram lambs through metabolism trial. Fifty six Deccani ram lambs were randomly divided into eight groups of seven each and offered either block or mash form of the four crop residue based diets for a period of 25 d. DMI (g/d, g/kg BW or g/kg W0.75) of complete diet was not influenced by the type of crop residue or cultivar. Physical form of the diet had significant influence on DMI being higher (20–29%) in lambs fed mash than block diets irrespective of crop residue and cultivar. Digestibility of DM, OM, CP and cell wall constituents (NDF and ADF) was influenced by the type of crop residue and cultivar but physical form (mash vs. block) of the diet had no significant effect on nutrient digestibility except CP. Intake of OM, DOM, CP (g/d) and ME (MJ/d) was significantly higher in sheep fed mash form of diets than block form irrespective of cultivar and crop residue in the diet. Type of crop residue has no influence on nutrient intake except DOMI but cultivar in the complete diet had influence on nutrient intake either significantly (DOM, CP; P<0.05) or non-significantly (OM, ME) being higher in Andhra hybrid sorghum stover than Telangana stover based diet. N balance was influenced by the type of crop residue, cultivar and physical form of the diet. N balance was significantly (P<0.05) higher in mash than block, Andhra hybrid than Telangana cultivar and SSBLR and sorghum stover based diets than those fed paddy straw based diets. The results of the present study revealed that type and cultivar (quality) of crop residue and physical form of the diet had influence either significantly or non-significantly on intake, nutrient utilization and N balance in growing Deccani sheep fed complete diets.

English

This study assessed the effects of storage method and storage duration on the dynamics in nutritional qualities of tef (Eragrostis tef-cereal indigenous to Ethiopia) and wheat straws in Ejere woreda, central highlands of Ethiopia. The trial was designed with a factorial combination of two storage methods (shelter shade, open-air) and four storage durations (zero, two, four and six months). A total of 12 farmers (six conserving tef straw and the rest six conserving wheat straw) were selected for sampling and evaluation of the crop residues. Among the six farmers conserving each of the crop residues, three of them stored the straws in open-air while the other three used shelter shade. All the measured parameters (DM, ash, CP, IVOMD, ME, NDF, ADF and lignin contents) were significantly (p<0.05) affected by storage method and storage durations. The CP, IVOMD and ME contents showed consistently decreasing trends with prolonged storage durations, with higher nutrient losses in straws stored in open air than those stored under shelter. The estimated losses in CP contents during the six months storage period, respectively when stored under shelter and in open air were 30.2 and 41% in tef straw; and 22.3 and 46.9% in wheat straw. Similarly, IVOMD was reduced by 35.8 and 41.1% in tef straw and by 33.3 and 42.6% in wheat straw when stored under shelter and in open air, respectively during the six months storage period. On the other hand, the fiber fractions showed increasing trends with prolonged storage durations, with higher rates of increase in straws stored in open air than those stored under shelter. During the six months storage period, NDF content was increased by 8.5 and 13.6% in tef straw and by 8.9 and 12.9% in wheat straw, respectively when stored under shelter and in open air. The ADF content was increased by 8.4 and 12.2% in tef straw and by 14.9 and 19.3% in wheat straw when stored under shelter and in open air condition, respectively. Lignin content was also increased by 14.2 and 53.1% in tef straw and by 37.7 and 32.2% in wheat straw when stored under shelter and in open air, respectively. The decrease in CP and IVOMD, and the increase in fiber fractions with prolonged storage durations in the crop residues could be attributed to the loss of readily soluble nutrients and the higher concentration of the fibrous materials in the feed DM mainly when stored in open air. The result revealed that quality of crop residues which is inherently low would be substantially reduced further during storage especially when stored in open air. Therefore, supplementation schemes should consider the storage method, storage duration and the associated dynamics in nutritional quality in crop residue-based feeding system of dairy cattle. Key words: Crop residues, nutritional quality, storage method, storage duration, tef and wheat straws.

Rain regime and soil type affect the C and N dynamics in soil columns that are covered with mixed-species mulches

Aims The role of precipitation on the decomposition of residue mulches is of primary importance for the adequate management of nutrients in no-tilled agrosystems. The objective of this work was to understand the interactions between water dynamics and crop residue quality and their effect on carbon (C) and nitrogen (N) mineralization.

Nitrogen fertilization affects silicon concentration, cell wall composition and biofuel potential of wheat straw

Nitrogen is an essential input factor required for plant growth and biomass production. However, very limited information is available on how nitrogen fertilization affects the quality of crop residues to be used as lignocellulosic feedstock. In the present study, straw of winter wheat plants grown at six different levels of nitrogen supply ranging from 48 to 288 kg nitrogen ha−1 was analyzed for major cell wall components and mineral elements. Enzymatic digestion of the straw was carried out to evaluate the saccharification efficiency. The nitrogen concentration in the straw dry matter increased linearly from 0.32% to 0.71% over the range of nitrogen treatments. Cellulose and hemicellulose were not affected by the nitrogen supply while lignin peaked at medium rates of nitrogen application. The nitrogen treatments had a distinct influence on the silicon concentration, which decreased from 2.5% to 1.5% of the straw dry matter when the nitrogen supply increased from 48 to 192 kg ha−1. No further decline in Si occurred at higher rates of nitrogen application. The most abundant metals in the straw were potassium and calcium and their concentrations almost doubled over the range of nitrogen supplies. The enzymatic saccharification efficiency was negatively correlated with the rate of nitrogen supply. We conclude that the level of nitrogen supply to wheat plants alters the composition of cell wall components in the straw and that this may result in reduced saccharification efficiency.