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1.
The effect of nitrogen (N) supply through animal and green manures on grain yield of winter wheat and winter rye was investigated from 1997 to 2004 in an organic farming crop rotation experiment in Denmark on three different soil types varying from coarse sand to sandy loam. Two experimental factors were included in the experiment in a factorial design: (1) catch crop (with and without), and (2) manure (with and without). The four-course crop rotation was spring barley undersown with grass/clover – grass/clover – winter wheat or wheat rye – pulse crop. All cuttings of the grass–clover were left on the soil as mulch. Animal manure was applied as slurry to the cereal crops in the rotation in rates corresponding to 40% of the N demand of the cereal crops.Application of 50 kg NH4–N ha?1 in manure increased average wheat grain yield by 0.4–0.9 Mg DM ha?1, whereas the use of catch crops did not significantly affect yield. The use of catch crops interacts with other management factors, including row spacing and weed control, and this may have contributed to the negligible effects of catch crops. There was considerable variation in the amount of N (100–600 kg N ha?1 year?1) accumulated in the mulched grass–clover cuttings prior to ploughing and sowing of the winter wheat. This was reflected in grain yield and grain N uptake. Manure application to the cereals in the rotation reduced N accumulation in grass–clover at two of the locations, and this was estimated to have reduced grain yields by 0.1–0.2 Mg DM ha?1 depending on site. Model estimations showed that the average yield reduction from weeds varied from 0.1 to 0.2 Mg DM ha?1. The weed infestation was larger in the manure treatments, and this was estimated to have reduced the yield benefit of manure application by up to 0.1 Mg DM ha?1. Adjusting for these model-estimated side-effects resulted in wheat grain yields gains from manure application of 0.7–1.1 Mg DM ha?1.The apparent recovery efficiency of N in grains (N use efficiency, NUE) from NH4–N in applied manure varied from 23% to 44%. The NUE in the winter cereals of N accumulated in grass–clover cuttings varied from 14% to 39% with the lowest value on the coarse sandy soil, most likely due to high rates of N leaching at this location. Both NUE and grain yield benefit in the winter cereals declined with increasing amounts of N accumulated in the grass–clover cuttings. The model-estimated benefit of increasing N input in grass–clover from 100 to 500 kg N ha?1 varied from 0.8 to 2.0 Mg DM ha?1 between locations. This is a considerably smaller yield increase than obtained for manure application, and it suggests that the productivity in this system may be improved by removing the cuttings and applying the material to the cereals in the rotation, possibly after digestion in a biogas reactor.Cereal grain protein content was increased more by the N in the grass–clover than from manure application, probably due to different timing of N availability. Green-manure crops or manures with a relatively wide C:N ratio may therefore be critical for ensuring sufficiently high protein contents in high yielding winter wheat for bread making.  相似文献   

2.
Biological nitrogen (N) fixation (BNF) by legumes in organic cropping systems has been perceived as a strategy to substitute N import from conventional sources. However, the N contribution by legumes varies considerably depending on legumes species, as well as local soil and climatic conditions. There is a lack of knowledge on whether the N contribution of legumes estimated using short-term experiments reflects the long-term effects in organic systems varying in fertility building measures. There is also limited information on how fertilizer management practices in organic crop rotations affect BNF of legumes. Therefore, this study aimed to estimate BNF in long-term experiments with a range of organic and conventional arable crop rotations at three sites in Denmark varying in climate and soils (coarse sand, loamy sand and sandy loam) and to identify possible causes of differences in the amount of BNF. The experiment included 4-year crop rotations with three treatment factors in a factorial design: (i) rotations, i.e. organic with a year of grass-clover (OGC), organic with a year of grain legumes (OGL), and conventional with a year of grain legumes (CGL), (ii) with (+CC) and without (−CC) cover crops, and (iii) with (+M) and without (−M) animal manure in OGC and OGL, and with (+F) mineral fertilizer in CGL. Cover crops consisted of a mixture of perennial ryegrass and clover (at the sites with coarse sand and sandy loam soils) or winter rye, fodder radish and vetch (at the site with loamy sand soil) in OGC and OGL, and only perennial ryegrass in CGL at all sites. The BNF was measured using the N difference method. The proportion of N derived from the atmosphere (%Ndfa) in aboveground biomass of clover grown for an entire year in a mixture with perennial ryegrass and harvested three times during the growing season in OGC was close to 100% at all three sites. The Ndfa of grain legumes in both OGL and CGL rotations ranged between 61% and 95% depending on location with mostly no significant difference in Ndfa between treatments. Cover crops had more than 92% Ndfa at all sites. The total BNF per rotation cycle was higher in OGC than in OGL and CGL, mostly irrespective of manure/fertilizer or cover crop treatments. There was no significant difference in total BNF between OGL and CGL rotations, but large differences were observed between sites. The lowest cumulated BNF by all the legume species over the 4-year rotation cycle was obtained at the location with sandy loam soil, i.e. 224–244, 96–128, and 144–156 kg N ha−1 in OGC, OGL and CGL, respectively, whereas it was higher at the locations with coarse sand and loamy sand soil, i.e. 320–376, 168–264, and 200–220 kg N ha−1 in OGC, OGL and CGL, respectively. The study shows that legumes in organic crop rotations can maintain N2 fixation without being significantly affected by long-term fertilizer regimes or fertility building measures.  相似文献   

3.
The reduction in crop diversity and specialization of cereal-based cropping systems have led to high dependence on synthetic nitrogen (N) fertilizer in many areas of the globe. This has exacerbated environmental degradation due to the uncoupling of carbon (C) and N cycles in agroecosystems. In this experiment, we assessed impacts of introducing grain legumes and cover crops to innovative cropping systems to reduce N fertilizer application while maintaining wheat yields and grain quality. Six cropping systems resulting from the combination of three 3-year rotations with 0, 1 and 2 grain legumes (GL0, GL1 and GL2, respectively) with (CC) or without (BF, bare fallow) cover crops were compared during six cropping seasons. Durum wheat was included as a common high-value cash crop in all the cropping systems to evaluate the carryover effects of rotation. For each cropping system, the water use efficiency for producing C in aerial biomass and yield were quantified at the crop and rotation scales. Several diagnostic indicators were analyzed for durum wheat, such as (i) grain yield and 1000-grain weight; (ii) aboveground biomass, grain N content and grain protein concentration; (iii) water- and N-use efficiencies for yield; and (iv) N harvest index. Compared to the GL0-BF cropping system, which is most similar to that traditionally used in southwestern France, N fertilizer application decreased by 58%, 49%, 61% and 56% for the GL1-BF, GL1-CC, GL2-BF and GL2-CC cropping systems, respectively. However, the cropping systems without grain legumes (GL0-BF and GL0-CC) had the highest water use efficiency for producing C in aerial biomass and yield. The insertion of cover crops in the cropping systems did not change wheat grain yield, N uptake, or grain protein concentration compared to those of without cover crops, demonstrating a satisfactory adaptation of the entire cropping system to the use of cover crops. Winter pea as a preceding crop for durum wheat increased wheat grain production by 8% (383 kg ha−1) compared to that with sunflower − the traditional preceding crop − with a mean reduction in fertilizer application of 40–49 kg N ha−1 during the six-year experiment. No differences in protein concentration of wheat grain were observed among preceding crops. Our experiment demonstrates that under temperate submediterranean conditions, properly designed cropping systems that simultaneously insert grain legumes and cover crops reduce N requirements and show similar wheat yield and grain quality attributes as those that are cereal-based.  相似文献   

4.
In a field experiment, peas (Pisum sativum L.) and oats (Avena sativa L.) were grown as sole crops and intercrops, fertilized with horse manure and yard-waste compost derived from shrub and garden cuttings at 10 t C ha−1 each. The objectives were to compare the effects of these organic fertilizer and cropping system in organic farming on (a) yield of peas and oats, grown as the sole crop or intercropped, as well as N2 fixation and photosynthetic rates, (b) the yield of wheat as a succeeding crop, (c) microbial biomass indices in soil and roots, and (d) microbial activity estimated by the CO2 evolution rate in the field and the amount of organic fertilizers, recovered as particulate organic matter (POM). In general, organic fertilizer application improved nodule dry weight (DW), photosynthetic rates, N2 fixation, and N accumulation of peas as well as N concentration in oat grain. Averaged across fertilizer treatments, pea/oat intercropping significantly decreased nodule DW, N2 fixation and photosynthetic rate of peas by 14, 17, and 12%, respectively, and significantly increased the photosynthetic rate of oats by 20%. However, the land equivalent ratio (LER) of intercropped peas and oats exceeded 1.0, indicating a yield advantage over sole cropping. Soil microbial biomass was positively correlated with pea dry matter yields both in sole and intercropped systems. Organic fertilizers increased the contents of microbial biomass C, N, P, and fungal ergosterol in soil and CO2 production, whereas the cropping system had no effects on these microbial indices. According to the organic fertilizer recovered as POM, 70% (manure) and 64% (compost) of added C were decomposed, but only 39% (manure) and 13% (compost) could be attributed to CO2–C during a 101-day period. This indicated that horse manure was more readily available to soil microorganisms than compost, leading to increased grain yields of the succeeding winter wheat.  相似文献   

5.
Nitrogen partitioning and utilization can partly control plant productivity. This study was conducted to estimate dry matter (DM) and N partitioning parameters in corn (Zea mays L.) as affected by N source, N timing, and crop rotation. We quantified yield by combine, aboveground DM accumulation [residues (stalk + cob) and grain], and C and N concentrations at growth stage R6 of corn continuously cropped (CC) or in rotation with soybean [Glycine max (L.) Merr.] (CS) and fertilized with side-dressed urea-ammonium nitrate (UAN) or with liquid swine manure applied in either spring (SM) or fall (FM). Of the assessed N partitioning parameters, N utilization showed the highest association with yield (r = 0.94***). Across treatment means, 72% of these increases in N utilization could be attributed to increases in N uptake. On the contrary, N harvest index (NHI) exhibited nearly constant values across experimental units, and therefore, NHI showed a minor relative contribution to variations in N utilization, thus supporting the basic premise of low NHI dependency on environment or management. Both N uptake and N utilization were driven by type of N addition (UAN > manure). Also, corn N utilization and yield were greater (10–13%) within the corn–soybean rotation, suggesting that a shift in land use from crop rotations into more continuous corn due to increasing demand for corn grain may impose additional challenges for enhancing plant N nutrition and sustaining yield.  相似文献   

6.
Because of the complexity of farming systems, the combined effects of farm management practices on nitrogen availability, nitrogen uptake by the crop and crop performance are not well understood. To evaluate the effects of the temporal and spatial variability of management practices, we used data from seventeen farms and projections to latent structures analysis (PLS) to examine the contribution of 11 farm characteristics and 18 field management practices on barley performance during the period 2009–2012. Farm types were mixed (crop-livestock) and arable and were categorized as old organic, young organic or conventional farms. The barley performance indicators included nitrogen concentrations in biomass (in grain and whole biomass) and dry matter at two growing stages. Fourteen out of 29 farm characteristics and field management practices analysed best explained the variation of the barley performance indicators, at the level of 56%, while model cross-validation revealed a goodness of prediction of 31%. Greater crop diversification on farm, e.g., a high proportion of rotational leys and pasture, which was mostly observed among old organic farms, positively affected grain nitrogen concentration. The highest average grain nitrogen concentration was found in old organic farms (2.3% vs. 1.7 and 1.4% for conventional and young organic farms, respectively). The total nitrogen translocated in grain was highest among conventional farms (80 kg ha−1 vs. 33 and 39 kg ha−1 for young and old organic farms, respectively). The use of mineral fertilizers and pesticides increased biomass leading to significant differences in average grain yield which became more than double for conventional farms (477 ± 24 g m−2) compared to organic farms (223 ± 37 and 196 ± 32 g m−2 for young and old organic farms, respectively). In addition to the importance of weed control, management of crop residues and the organic fertilizer application methods in the current and three previous years, were identified as important factors affecting the barley performance indicators that need closer investigation. With the PLS approach, we were able to highlight the management practices most relevant to barley performance in different farm types. The use of mineral fertilizers and pesticides on conventional farms was related to high cereal crop biomass. Organic management practices in old organic farms increased barley N concentration but there is a need for improved management practices to increase biomass production and grain yield. Weed control, inclusion of more leys in rotation and organic fertilizer application techniques are some of the examples of management practices to be improved for higher N concentrations and biomass yields on organic farms.  相似文献   

7.
Integrated crop–livestock systems can help achieve greater environmental quality from disparate crop and livestock systems by recycling nutrients and taking advantage of synergies between systems. We investigated crop and animal production responses in integrated crop–livestock systems with two types of winter cover cropping (legume-derived N and inorganic fertilizer N), two types of tillage [conventional disk (CT) and no tillage (NT)], and whether cover crops were grazed by cow/calf pairs or not. The 13-ha field study was a modification of a previous factorial experiment with four replications on Ultisols in Georgia, USA. Recurring summer drought severely limited corn and soybean production during all three years. Type of cover crop had little influence and grazing of cover crops had minor influence on crop production characteristics. Cattle gain from grazing of winter cover crops added a stable component to production. No-tillage management had large positive effects on corn grain (95 vs. 252 g m−2 under CT and NT, respectively) and stover (305 vs. 385 g m−2) production, as well as on soybean grain (147 vs. 219 g m−2) and stover (253 vs. 375 g m−2) production, but little overall effect on winter wheat grain (292 g m−2) and stover (401 g m−2) production. Our results suggest that robust, diversified crop–livestock systems can be developed for impoverished soils of the southeastern USA, especially when managed under no tillage to control environmental quality and improve resistance of crops to drought.  相似文献   

8.
The adverse effects of climate change are significantly decreasing yield levels and yield stability over time in current monocropping systems. Intercropping (IC), i.e. growing more than one species simultaneously in the same field, often increases resource use efficiency and agricultural productivity compared with growing the component crops solely and can enhance yield stability. This meta-analysis of published IC literature quantified and analysed yield stability in IC compared with the respective sole crops, focusing on the effect of intercrop components (e.g. cereal-grain legume, non-cereal-grain legume), experimental patterns (e.g. experiment over years, experiment over locations), IC design (e.g. additive and replacement) and climatic zone (e.g. tropical, subtropical, and temperate). In total, 33 articles were analysed. The coefficient of variation (%CV) of yields was used for assessing yield stability, with lower CV value indicating higher yield stability. The analysis showed that cereal-grain legume IC (CV = 22.1) significantly increased yield stability compared with the respective grain legume sole crops (CV = 31.7). Moreover, compared with the respective cereal and legume sole crops, IC in the cereal-grain legume systems gave higher yield stability than IC in the non-cereal-grain legume systems. Compared with the respective cereal (CV = 25.3) and legume (CV = 30.3) sole crops, IC (CV = 19.1) in a replacement design had significantly (P < 0.05) higher yield stability. Also intercropping in replacement design gave more stable yields than IC in an additive design. In tropical regions, cereal sole crops (CV = 26.3) showed lower yield stability than IC (CV = 17.7) and legume sole crops (CV = 21.7). However, IC in all climatic zones showed higher yield stability than both sole crops. Moreover in our analysis, it was found that a higher yield level provided higher yield stability in crop production. Thus, increasing crop diversification through IC of cereals and grain legumes can enhance yield stability and food security, making an important contribution to eco-functional, ecological or sustainable intensification of global food production.  相似文献   

9.
The effect of spring application of separated liquid pig manure (LPM) in combination with medium to high levels of inorganic nitrogen (N) to winter wheat was investigated in a field trial study at two sites in two successive growing seasons (2007–2008). The key crop parameters examined were crop N uptake (CNU), N use efficiency and grain yield. The LPM product (3.5–4.0 g/kg total N) was applied at three application rates: 15, 30 and 45 m3/ha using a band spread application technique. The LPM was used in combination with reduced and recommended inorganic N levels; a zero N control was also included. Weather conditions in both seasons were similar with below average rainfall levels in spring followed by above average summer rainfall levels. The zero N control gave lowest CNU levels in both growing seasons (70–88 kg N/ha). Inorganic N application at the reduced and recommended N rates increased CNU levels by approximately 100 kgN/ha and 112 kgN/ha, respectively compared to the untreated control. Liquid pig manure application resulted in an additional crop uptake of 58 kgN/ha. Nitrogen use efficiencies for LPM ranged from 23 to 56% while inorganic N use efficiency levels were higher ranging from 58 to 73%. Lowest grain yield levels were measured from the zero N control (range 3.95–5.01 t/ha). The application of inorganic N increased grain yield levels by a minimum of 4.05 t/ha with LPM usage increasing grain yield levels by an additional 0.2–1.09 t/ha. This study showed that LPM could be successfully used in combination with inorganic fertilisers for the improved N nutrition of winter wheat in spring as part of an integrated nutrient programme.  相似文献   

10.
This work was aimed at providing a sustainable approach in the use of manure in irrigated maize crop under Mediterranean climatic conditions. To this end, the effect of continuous annual applications of dairy cattle manure, combined or not with mineral N fertilizer, on the following parameters was studied: grain yield, grain and plant N concentration, N uptake by plant, N use efficiency, and soil N and organic carbon. The experiment was conducted in a furrow-irrigated sandy soil under dry Mediterranean conditions during seven years. Three different rates of cattle manure (CM): 0, 30 and 60 Mg ha−1, were applied each year before sowing. These CM rates were combined with four mineral N rates (0, 100, 200 and 300 kg N ha−1) applied at sidedress.On average, the highest grain yields during the 7 years were obtained with the combination of CM at 30 Mg ha−1 and mineral fertilizer and with CM at 60 Mg ha−1 without mineral fertilizer. With CM at 30 Mg ha−1, mineral fertilizer increased yields during most of the growing seasons, meanwhile with CM at 60 Mg ha−1, there was not any significant effect of the joint application of mineral fertilizer on yields. Overall, best results were obtained exceeding maximum rates according to present legislation. The mean apparent nitrogen recovery (ANR) fraction during the 7 seasons was 29% for N exclusively applied as CM. Overall, increased N rates applied as CM resulted in decreased ANRs. However, ANR with CM at 30 and 60 Mg ha−1 increased during the first two seasons. This increased ANR ascribed to mineralization of residual organic N applied in previous seasons explained the increasing yields observed in the treatments along the study.The application of CM during 7 years increased the soil organic carbon in the first 30 cm by 5.7 and 9.9 Mg ha−1 with CM at 30 and 60 Mg ha−1, respectively, when compared to the initial stock. Thus, manure-based fertilization could be an alternative to mineral fertilizer in order to achieve high maize yields while improving soil quality under dry Mediterranean conditions.  相似文献   

11.
Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha−1) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha−1 than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha−1. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha−1. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha−1 than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha−1 than in rye and weeds with 0 or 60 kg N ha−1. Increased N supplied by hairy vetch or 120–130 kg N ha−1 increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha−1. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha−1. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.  相似文献   

12.
A field experiment comparing different arable crop rotations was conducted in Denmark during 1997–2008 on three sites varying in climatic conditions and soil types, i.e. coarse sand (Jyndevand), loamy sand (Foulum), and sandy loam (Flakkebjerg). The crop rotations followed organic farm management, and from 2005 also conventional management was included for comparison. Three experimental factors were included in the experiment in a factorial design: 1) crop rotation (organic crop rotations varying in use of whole-year green manure (O1 and O2 with a whole-year green manure, and O4 without), and a conventional system without green manure (C4)), 2) catch crop (with and without), and 3) manure (with and without). The experiment consisted of three consecutive cycles using four-course rotations with all crops present every year, i.e. 1997–2000 (1st cycle), 2001–2004 (2nd cycle), and 2005–2008 (3rd cycle). In the 3rd cycle at all locations C4 was compared with two organic rotations, i.e. O2 and O4. The O2 rotation in the third cycle included spring barley, grass-clover, potato, and winter wheat, whereas C4 and O4 included spring barley, faba bean, potato, and winter wheat. For the O2 rotation with green manure there was a tendency for increased DM yield over time at all sites, whereas little response was seen in N yield. In the O4 rotation DM and N yields tended to increase at Foulum over time, but there was little change at Flakkebjerg. The DM yield gap between organic and conventional systems in the 3rd cycle varied between sites with 34–66% at Jyndevad, 21–44% at Foulum, and 32–52% at Flakkebjerg. The inclusion of grass-clover resulted in lower cumulated yield over the rotation than the treatment without grass-clover. The use of manure reduced the DM yield gap between conventional and organic systems on an average by 15 and 21%-points in systems with and without grass-clover, respectively, and the use of catch crops reduced the yield gap by 3 and 5%-points in the respective systems. Across all crops the agronomic efficiency of N in manure (yield benefit for each kg of mineral N applied) was greater in O4 compared with O2 for all crops.  相似文献   

13.
Soil fertility and climate risks are hampering crop production in the Sahelian region. Because experiments with only a few fertility management options on a limited number of sites and years cannot fully capture the complex and highly non-linear soil–climate–crop interactions, crop growth simulation models may suitably complement experimental research to support decision making regarding soil fertility and water management. By means of a long term (23 years) scenario analysis using the Agricultural Production Systems Simulator (APSIM) model, this study investigates millet response to N in view of establishing N recommendations better adapted to subsistence small-holder millet farming in the Sahel. Prior to this, the APSIM model was tested on a rainfed randomized complete block experiment carried out during the 1994 and 1995 cropping seasons, having contrasting rainfall conditions. The experiment combined, at three levels each, the application of cattle manure (300, 900 and 2700 kg ha?1), millet residue (300, 900 and 2700 kg ha?1) and mineral fertilizer (unfertilized control, 15 kg N ha?1 + 4.4 kg P ha?1 and 45 kg N ha?1 + 13.1 kg P ha?1) at ICRISAT Sahelian Center, Niger. The model suitably predicted plant available water PAW and the simulated water and nitrogen stress were in agreement with measurement (water) and expectation (N) regarding the fertilizer and rainfall conditions of the experiment. APSIM simulations were in satisfactory agreement with the observed crop growth except for the highest crop residue application rates (>900 kg ha?1). For biomass and grain yield, the model performance was relatively good in 1994 but biomass yields were slightly overpredicted in 1995. The model was able to adequately reproduce the average trend of millet grain yield response to N inputs from manure and fertilizer, and to predict the overall observed higher grain yield in 1995 compared to 1994, despite the better rainfall in 1994. The 23-year, long term scenario analysis combining different application rates of cattle manure, millet residue and mineral fertilizer, showed that moderate N application (15 kg N ha?1) improves both the long term average and the minimum yearly guaranteed yield without increasing inter-annual variability compared to no N input. Although it does imply a lower average yield than at 30 kg N ha?1, the application of 15 kg N ha?1 appears more appropriate for small-holder, subsistence farmers than the usual 30 kg N ha?1 recommendation as it guarantees higher minimum yield in worst years, thereby reducing their vulnerability.  相似文献   

14.
The Nitrates Directive (91/676/EEC, Anonymous, 1991) was developed in Europe to limit environmental threats from intensive livestock farming and N fertilizer applications to crops. It imposed several rules on farmers and public bodies, one of which was nutrient fertilization plan adoption. Here we use results from the Tetto Frati (Northern Italy) Long-Term Experiment to verify the terms and coefficients in the official Italian guidelines and evaluate the limitations imposed to organic fertilization amounts. For this purpose, we mined long-term experimental data of crop yield, N uptake, N use efficiency, and soil organic matter content from miscellanea cropping systems fertilized with farmyard manure (FYM) and bovine slurry (SLU), typical of a dairy farm in Northern Italy. N fertilization efficiency indicators (Removal to Fertilizer ratio, Apparent Recovery and Nitrogen Fertilizer Replacement Value) indicated that in the long run, FYM behaved similarly to urea, and better than SLU. Even N supply rates as high as 250 kg N ha−1 were justified by high rates of crop removal. In fact, among the terms of the mass-balance equation, SOM mineralization was found to be most relevant, followed by meadow rotation residual effects. We conclude that a revised Nitrates Directives application scheme could be more relaxed in its application limit of manure-N, but should be more ambitious in setting efficiency coefficients for manure fertilization.  相似文献   

15.
The efficient use by crops of nitrogen from manures is an agronomic and environmental issue, mainly in double-annual forage cropping systems linked to livestock production. A six-year trial was conducted for a biennial rotation of four forage crops: oat-sorghum (first year) and ryegrass-maize (second year) in a humid Mediterranean area. Ten fertilization treatments were introduced: a control (without N); two minerals equivalent to 250 kg N ha−1 year−1 applied at sowing or as sidedressing; dairy cattle manure at a rate of 170, 250 and 500 kg N ha−1 year−1 and four treatments where the two lowest manure rates were supplemented with 80 or 160 kg mineral N ha−1 year−1. They were distributed according to a randomized block design with three blocks. The highest N mineral soil content was found in the summer of the third rotation, in plots where no manure was applied. The yearly incorporation of manure reduced, in successive cropping seasons, the amount of additional mineral N needed as sidedressing to achieve the highest yields. Besides, in the last two years, there was no need for mineral N application for the manure rate of 250 kg N ha−1 year−1. This amount always covered the oat-sorghum N uptake. In the ryegrass-maize sequence uptakes were as high as 336 kg N ha−1 year−1. In the medium term, the intermediate manure rate (250 kg N ha−1 year−1) optimizes nutrient recycling within the farming system, and it should be considered in the analysis of thresholds for N of organic origin to be applied to systems with high N demand.  相似文献   

16.
The major objective for clover in a winter wheat/white clover intercropping system is to supply nitrogen (N) for the wheat. A field experiment was repeated in 2 years on a loamy sand in Denmark to investigate the possibilities for increasing N supply to the winter wheat by cutting and mulching the clover between the wheat rows. The clover was cut with a weed brusher on three different dates in each year.Intercropped wheat with unbrushed clover had a lower grain yield than wheat as a sole crop. Brushing increased wheat N uptake and wheat grain yields. Intercropping with two or three brushing dates gave higher wheat yields than wheat as the sole crop. The largest increases in grain N uptake, 21–25 kg N ha−1, were obtained for the brushings around wheat flag leaf emergence. The highest yield increases with a single brushing, 0.98–1.11 Mg DM ha−1, were obtained when brushing was performed during the stem elongation phase. The largest grain yields for treatments with two brushings were obtained with a first brushing at start of stem elongation and a second around flag leaf emergence. The first brushing probably provided N to increase the wheat leaf area index and thus the light interception, while the second brushing provided N to sustain the leaf area during grain filling and reduced clover biomass and therefore competition for water. Intercropping wheat and clover increased grain N concentrations by 0.11–0.39%-point compared with wheat as a sole crop. Intercropping may thus offer possibilities for improving the bread-making quality of organically grown wheat.  相似文献   

17.
Although producers’ prime objective may be to increase net returns, many are also interested in conserving and enhancing the quality the soil, water and air resources through adopting more environmentally friendly production practices. This study compared non-renewable energy inputs, energy output, and energy use efficiency of nine dryland cropping systems comprised of a factorial combination of three methods of input management [high (HIGH), i.e., conventional tillage plus full recommended rates of fertilizer and pesticides; reduced (RED), i.e., conservation tillage plus reduced rates of fertilizer and pesticides; and organic (ORG), i.e., conventional tillage plus N-fixing legumes and non-chemical means of weed and pest control]; and three crop rotation systems with varying levels of cropping diversity [a fallow-based rotation with low crop diversity (LOW); a diversified rotation using annual cereal, oilseed and pulse grains (DAG); and a diversified rotation using annual grains and perennial forages (DAP)]. The study was conducted over the 1996–2007 period on a Dark Brown Chernozemic soil (Typic Boroll) in the Canadian Prairies. As expected, total direct plus indirect energy input was the highest for the HIGH and RED input treatments (3773 MJ ha?1 year?1), and 50% less for ORG management. Most of the energy savings came from the non-use of inorganic fertilizers and pesticides in the ORG management treatments. Further, total energy use was the highest for the DAG treatments (3572 MJ ha?1 year?1), and similar but about 18% lower for the DAP and LOW crop diversity treatments compared to DAG. Thus, overall, the HIGH/DAG and RED/DAG systems had the highest energy requirements (4409 MJ ha?1 year?1) and ORG/DAP had the lowest (1806 MJ ha?1 year?1). Energy output (calorimetric energy content) was typically the highest for the HIGH input treatments (26,541 MJ ha?1 year?1), was about 4% less with RED, and 37% less with ORG management. The latter reflected the lower crop yields obtained with organic management. Similarly, energy output was the highest for the DAP treatments (25,008 MJ ha?1 year?1), about 5% less for DAG, and 20% less for the LOW crop diversity treatments. The higher energy output with the DAP treatments largely reflected that the entire harvested biomass of the forage crops was included in energy output, while for grain crops only the seed was included. The straw and crop residues from annual crops were returned to the land to protect the soil from erosion and to maintain soil organic matter as this is the recommended practice in this semi-arid region. In contrast to energy output and to net energy produced, energy use efficiency (measured as yield of grain plus forage produced per unit of energy input or as energy output/energy input ratio) was the highest for the ORG input treatments (497 kg of harvested production GJ?1 of energy input, and an energy output/energy input ratio of 8.8). We obtained lower, but generally similar energy use efficiency for the HIGH and RED input treatments (392 kg GJ?1 and ratio of 7.1). Thus, overall, ORG/DAP was the most energy efficient cropping system, while RED/LOW and RED/DAG generally ranked the lowest in energy use efficiency. Our findings support the current movement of producers toward ORG management as a means of reducing the reliance on non-renewable energy inputs and improving overall energy use efficiency of their cropping systems. Our results also suggest that moving away from traditional monoculture cereal rotations that employ frequent summer fallowing, toward extended and diversified crop rotations that use reduced tillage methods, although resulting in an increase in energy output, will not significantly reduce the overall reliance on non-renewable energy inputs, nor enhance energy use efficiency, unless perennial legume forages and/or legume grain crops are included in the cropping mix.  相似文献   

18.
APSIM Nwheat is a crop system simulation model, consisting of modules that incorporate aspects of soil water, nitrogen (N), crop residues, and crop growth and development. The model was applied to simulate above- and below-ground growth, grain yield, water and N uptake, and soil water and soil N of wheat crops in the Netherlands. Model outputs were compared with detailed measurements of field experiments from three locations with two different soil types. The experiments covered two seasons and a range of N-fertiliser applications. The overall APSIM Nwheat model simulations of soil mineral N, N uptake, shoot growth, phenology, kernels m−2, specific grain weight and grain N were acceptable. Grain yields (dry weight) and grain protein concentrations were well simulated with a root mean square deviation (RMSD) of 0.8 t ha−1 and 1.6 protein%, respectively. Additionally, the model simulations were compared with grain yields from a long-term winter wheat experiment with different N applications, two additional N experiments and regional grain yield records. The model reproduced the general effects of N treatments on yields. Simulations showed a good consistency with the higher yields of the long-term experiment, but overpredicted the lower yields. Simulations and earlier regional yields differed, but they showed uniformity for the last decade.In a simulation experiment, the APSIM Nwheat model was used with historical weather data to study the relationship between rate and timing of N fertiliser and grain yield, grain protein and soil residual N. A median grain yield of 4.5 t ha−1 was achieved without applying fertiliser, utilising mineral soil N from previous seasons, from mineralisation and N deposition. Application of N fertiliser in February to increase soil mineral N to 140 kg N ha−1 improved the median yield to 7.8 t ha−1 but had little effect on grain protein concentration with a range of 8–10%. Nitrogen applications at tillering and the beginning of stem elongation further increased grain yield and in particular grain protein, but did not affect soil residual N, except in a year with low rainfall during stem elongation. A late N application at flag leaf stage increased grain protein content by several per cent. This increase had only a small effect on grain yield and did not increase soil residual N with up to 40 kg N ha−1 applied, except when N uptake was limited by low rainfall in the period after the flag leaf stage. The economic and environmental optima in winter wheat were identified with up to 140 kg N ha−1 in February, 90 kg N ha−1 between tillering and beginning of stem elongation and 40 kg N ha−1 at flag leaf stage resulting in a median of 8.5 t ha−1 grain yield, 14.0% grain protein and 13 kg N ha−1 soil residual N after the harvest. The maximum simulated yield with maximum N input from two locations in the Netherlands was 9.9 t ha−1.  相似文献   

19.
Different preceding crops interact with almost all husbandry and have a major effect on crop yields. In order to quantify the yield response of winter wheat, a field trial with different preceding crop combinations (oilseed rape (OSR)–OSR–OSR–wheat–wheat–wheat), two sowing dates (mid/end of September, mid/end of October) and 16 mineral nitrogen (N) treatments (80–320 kg N ha−1) during 1993/1994–1998/1999, was carried out at Hohenschulen Experimental Station near Kiel in NW Germany. Single plant biomass, tiller numbers m−2, biomass m−2, grain yield and yield components at harvest were investigated. During the growing season, the incidence of root rot (Gaeumannomyces graminis) was observed. Additionally, a bioassay with Lemna minor was used to identify the presence of allelochemicals in the soil after different preceding crops.Averaged over all years and all other treatments, wheat following OSR achieved nearly 9.5 t ha−1, whereas the second wheat crop following wheat yielded about 0.9 t ha−1 and the third wheat crop following 2 years of wheat about 1.9 t ha−1 less compared with wheat after OSR. A delay of the sowing date only marginally decreased grain yield by 0.2 t ha−1. Nitrogen fertilization increased grain yield after all preceding crop combinations, but at different levels. Wheat grown after OSR reached its maximum yield of 9.7 t ha−1 with 210 kg N ha−1. The third wheat crop required a N amount of 270 kg N ha−1 to achieve its yield maximum of 8.0 t ha−1.Yield losses were mainly caused by a lower ear density and a reduced thousand grain weight. About 4 weeks after plant establishment, single wheat plants following OSR accumulated more biomass compared to plants grown after wheat. Plants from the third wheat crop were smallest. This range of the preceding crop combinations was similar at all sampling dates throughout the growing season.Root rot occurred only at a low level and was excluded to cause the yield losses. The Lemna bioassay suggested the presence of allelochemicals, which might have been one reason for the poor single plant development in autumn.An increased N fertilization compensated for the lower number of ears m−2 and partly reduced the yield losses due to the unfavorable preceding crop combination. However, it was not possible to completely compensate for the detrimental influences of an unfavorable preceding crop on the grain yield of the subsequent wheat crop.  相似文献   

20.
Depending on soil and management, ploughing up grassland for use as arable land can lead to an increase in the release of mineralized nitrogen and a high risk of nitrogen leaching during winter. The amount of N leaching is also dependent on the N efficiency of following crops and the level of N fertilization.In a field experiment in northwest Germany permanent grassland was ploughed and used as arable land. The experiment was conducted over 2 years at three sites and investigated two main factors: (i) succeeding crops, either spring barley (and catch crop)–maize or silage maize–maize; and (ii) N-fertilization either nil or moderate (120 kg N ha−1 for barley or 160 kg for maize). Plant yields, the soil mineral nitrogen (SMN) content and the nitrate leaching losses over winter were determined. On average for the 2-year period, the SMN in autumn and the nitrate leaching losses during winter for the rotation barley–maize were 76 kg ha−1 SMN and 81 kg N ha−1 N leaching losses, and for maize–maize they amounted to 108 and 113 kg ha−1, respectively. The SMN and N leaching losses for the plots with no N fertilizer were 49 and 52 kg N ha−1 and for the plots fertilized at a moderate N level they were 135 and 142 kg N ha−1, respectively.We conclude that although the extent of nitrate leaching is influenced by the site conditions and management of the grassland prior to ploughing, the management after ploughing is the decisive factor. The farmer can significantly reduce nitrate leaching with his choice of succeeding crop and the amount of N fertilization.  相似文献   

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