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1.
In Jiangsu province, Southeast China, high irrigated rice yields (6–8000 kg ha−1) are supported by high nitrogen (N) fertilizer inputs (260–300 kg N ha−1) and low fertilizer N use efficiencies (recoveries of 30–35%). Improvement of fertilizer N use efficiency can increase farmers’ profitability and reduce negative environmental externalities. This paper combines field experimentation with simulation modeling to explore N fertilizer management strategies to realize high yields, while increasing N use efficiency. The rice growth model ORYZA2000 was parameterized and evaluated using data from field experiments carried out in Nanjing, China. ORYZA2000 satisfactorily simulated yield, crop biomass and crop N dynamics, and the model was applied to explore options for different N-fertilizer management regimes, at low and high levels of indigenous soil N supply, using 43 years of historical weather data.On average, yields of around 10–11,000 kg ha−1 were realized (simulated and in field experiments) with fertilizer N rates of around 200 kg ha−1. Higher fertilizer doses did not result in substantially higher yields, except under very favorable weather conditions when yields exceeding 13,000 kg ha−1 were calculated. At fertilizer rates of 150–200 kg ha−1, and at the tested indigenous soil N supplies of 0.6–0.9 kg ha−1 day−1, high fertilizer N recovery (53–56%), partial N productivity (50–70 kg kg−1) and agronomic N use efficiency (20–30 kg kg−1) were obtained with application in three equal splits at transplanting, panicle initiation and booting. Increasing the number of splits to six did not further increase yield or improve any of the N use efficiency parameters.  相似文献   

2.
Efficient N management is essential to optimize yields and reduce degradation of the environment, but requires knowledge of deficit irrigation effects on crop yields and crop N outputs. This study assessed the N content and N-use efficiency of cotton over the 2008 and 2009 growing seasons in a single field site of the Thessaly Plain (central Greece). The experiment consisted of nine treatments with three fertilizer rates (60, 110 and 160 kg N ha−1) split into three irrigation levels (approx. 1.0, 0.7 and 0.4 of the amount applied by the producer). Reduced water supply induced a shift in the distribution of N within the plant with seeds becoming an N sink under conditions of water stress. Total crop N increased linearly with irrigation level and reached a maximum average of 261 and 192 kg N ha−1 in 2008 and 2009, respectively. Fertilizer application did not trigger a crop N or yield response and indicated that N inputs were in excess of crop needs. Variation in weather patterns appeared to explain annual differences of nitrate-N in the top soil and N uptake by the crop.The index of lint production efficiency (iNUE) detected crop responses caused by irrigation and annual effects, but failed to account for excessive N inputs due to mineral fertilizer applications. A maximum average iNUE of 9.6 was obtained under deficit irrigation, whereas an iNUE of 8.1 was obtained under 40 cm irrigation when crop N uptake was not excessive (192 kg ha−1 in 2009). In contrast, NUE, as an estimator of N recovery efficiency, identified excessive fertilizer inputs as N losses to the environment and indicated that 60 kg N ha−1 was a rate of high N removal efficiency and long-term N balance. However, NUE failed to account for crop N responses to irrigation and weather/management patterns. In this case study, neither index was able to detect all the factors influencing the N mass balance and both were required in order to provide a comprehensive evaluation of the environmental performance of our cropping system.  相似文献   

3.
Questions as to which crop to grow, where, when and with what management, will be increasingly challenging for farmers in the face of a changing climate. The objective of this study was to evaluate emergence, yield and financial benefits of maize, finger millet and sorghum, planted at different dates and managed with variable soil nutrient inputs in order to develop adaptation options for stabilizing food production and income for smallholder households in the face of climate change and variability. Field experiments with maize, finger millet and sorghum were conducted in farmers’ fields in Makoni and Hwedza districts in eastern Zimbabwe for three seasons: 2009/10, 2010/11 and 2011/12. Three fertilization rates: high (90 kg N ha−1, 26 kg P ha−1, 7 t ha−1 manure), low (35 kg N ha−1, 14 kg P ha−1, 3 t ha−1 manure) and a control (zero fertilization); and three planting dates: early, normal and late, were compared. Crop emergence for the unfertilized finger millet and sorghum was <15% compared with >70% for the fertilized treatments. In contrast, the emergence for maize (a medium-maturity hybrid cultivar, SC635), was >80% regardless of the amount of fertilizer applied. Maize yield was greater than that of finger millet and sorghum, also in the season (2010/11) which had poor rainfall distribution. Maize yielded 5.4 t ha−1 compared with 3.1 t ha−1 for finger millet and 3.3 t ha−1 for sorghum for the early plantings in the 2009/10 rainfall season in Makoni, a site with relatively fertile soils. In the poorer 2010/11 season, early planted maize yielded 2.4 t ha−1, against 1.6 t ha−1 for finger millet and 0.4 t ha−1 for sorghum in Makoni. Similar yield trends were observed on the nutrient-depleted soils in Hwedza, although yields were less than those observed in Makoni. All crops yielded significantly more with increasing rates of fertilization when planting was done early or in what farmers considered the ‘normal window’. Crops planted early or during the normal planting window gave comparable yields that were greater than yields of late-planted crops. Water productivity for each crop planted early or during the normal window increased with increase in the amount of fertilizer applied, but differed between crop type. Maize had the highest water productivity (8.0 kg dry matter mm−1 ha−1) followed by sorghum (4.9 kg mm−1 ha−1) and then finger millet (4.6 kg mm−1 ha−1) when a high fertilizer rate was applied to the early-planted crop. Marginal rates of return for maize production were greater for the high fertilization rate (>50%) than for the low rate (<50%). However, the financial returns for finger millet were more attractive for the low fertilization rate (>100%) than for the high rate (<100%). Although maize yield was greater compared with finger millet, the latter had a higher content of calcium and can be stored for up to five years. The superiority of maize, in terms of yields, over finger millet and sorghum, suggests that the recommendation to substitute maize with small grains may not be a robust option for adaptation to increased temperatures and more frequent droughts likely to be experienced in Zimbabwe and other parts of southern Africa.  相似文献   

4.
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   

5.
Data from a field experiment (1995–2000) conducted on a fertile sandy loess in the Hercynian dry region of central Germany were used to determine the energy efficiency of winter oilseed rape (Brassica napus L.) as affected by previous crop and nitrogen (N) fertilization. Depending on the previous crop, winter oilseed rate was cultivated in two different crop rotations: (1) winter barley (Hordeum vulgare L.)–winter oilseed rape–winter wheat (Triticum aestivum L.), and (2) pea (Pisum sativum L.)–winter oilseed rape–winter wheat. Fertilizer was applied to winter oilseed rape as either calcium ammonium nitrate (CAN) or cattle manure slurry. The N rates applied to winter oilseed rape corresponded to 0, 80, 160 and 240 kg N ha−1 a−1.Results revealed that different N management strategies influenced the energy balance of winter oilseed rape. Averaged across years, the input of energy to winter oilseed rape was highly variable ranging from 7.42 to 16.1 GJ ha−1. Lowest energy input occurred when unfertilized winter oilseed rape followed winter barley, while the highest value was obtained when winter oilseed rape received 240 kg N ha−1 organic fertilization and followed winter barley. The lowest energy output (174 GJ ha−1), energy from seed and straw of winter oilseed rape, was observed when winter oilseed rape receiving 80 kg N ha−1 as organic fertilizer followed winter barley. The energy output increased to 262 GJ ha−1 for winter oilseed rape receiving 240 kg N ha−1 as mineral fertilizer followed pea. The energy efficiency was determined using the parameters energy gain (net energy output), energy intensity (energy input per unit grain equivalent GE; term GE is used to express the contribution that crops make to the nutrition of monogastric beings), and output/input ratio. The most favourable N rate for maximizing energy gain (250 GJ ha−1) was 240 kg N ha−1, while that needed for minimum energy intensity (91.3 MJ GE−1) was 80 kg N ha−1 and for maximum output/input ratio (29.8) was 0 kg N ha−1.  相似文献   

6.
In the rainfed mid-hill region of Nepal, most fields receive 2–3 t ha−1 of organic compost application every year. Despite efficient recovery and use of organics in the mixed crop-animal systems that predominant in the mid-hills, depleted soil fertility is widely understood to be a significant constraint to crop productivity, with most farmers achieving maize grain yields below 2 t ha−1. Increased use of fertilizer may arrest and even reverse long-term soil quality degradation, but few farmers in the mid-hills use them at present and existing recommendations are insufficiently responsive to site, varietal, and management factors that influence the productivity and profitability of increased fertilizer use. Moreover, policy makers and development practitioners often hold the perception that returns to fertilizer use in the mid-hills are too low to merit investment. In this study, on-farm experiments were conducted at 16 sites in the Palpa district, Nepal to assess the responsiveness of a maize hybrid (DKC 9081) and an ‘improved’ open-pollinated maize variety (‘OPV’, Manakamana-3) to four nitrogen (N) rates, i.e., 0, 60, 120 and 180 kg ha−1, with each N rate response evaluated at 30:30 and 60:60 kg ha−1 rates of phosphorus (P2O5) and potassium (K2O), respectively. With sound agronomy and high rates of fertilizer (180:60:60 kg N:P2O5:K2O ha−1), grain yields observed in the field experiments exceeded 8 t ha−1 with hybrids and 6 t ha−1 with OPV. Yield levels were lower for OPV than hybrid at every level of applied N, but both genotypes responded linearly to N with partial factor productivity for N (PFPN) ranging from 14 to 19 for OPV versus 26–30 for hybrid, with improved N efficiencies obtained when P and K rates were significantly higher. Averaged across phosphorus (P) and potassium (K) levels, a $ 1 incremental investment in fertilizer increased the gross margin (GM) by $ 1.70 ha−1 in OPV and by $ 1.83 ha−1 in the hybrid. For the full response of N, requires higher rate of P2O5:K2O and vice-versa and full response to P2O5:K2O does not occur if N is absent. These results suggest that, i) degraded soils in the mid-hills of Nepal respond favorably to macronutrient fertilizers – even at high rates, ii) balanced fertilization is necessary to optimize returns on investments in N but must be weighed against additional costs, iii) OPVs benefit from investments in fertilizer, albeit at a PFPN that is 36–47% lower than for hybrids, and, consequently iv) hybrids are an effective mechanism for achieving a higher return on fertilizer investments, even when modest rates are applied. To extend these findings across years and sites in the mid-hills, crop growth simulations using the CERES-maize model (DSSAT) were conducted for 11 districts with historical weather and representative soils data. Average simulated (hybrid) maize yields with high fertilizer rate (180:60:60 kg N:P2O5:K2O ha−1) ranged from 3.9 t ha−1 to 7.5 t ha−1 across districts, indicating a high disparity in attainable yield potential. By using these values to estimate district-specific attainable yield targets, recommended N fertilizer rates vary between 65 and 208 kg N ha−1, highlighting the importance of developing domain-specific recommendations. Simulations also suggest the potential utility of using weather forecasts in tandem with site and planting date information to adjust fertilizer recommendations on a seasonal basis.  相似文献   

7.
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   

8.
One experiment lasting for two years was carried out at Pegões (central Portugal) to estimate the impact of mature white lupine residue (Lupinus albus L.) on yield of fodder oat (Avena sativa L. cv. Sta. Eulalia) as the next crop in rotation, comparing with the continuous cultivation of cereal, under two tillage practices (conventional tillage and no-till) and fertilized with five mineral nitrogen (N) rates, with three replicates. Oat as a first crop in the rotation provided more N to the agro-ecosystem (63 kg N ha−1) than did lupine (30–59 kg N ha−1). This was at a cost of 100 kg of mineral N ha−1, whereas lupine was grown without addition of N. A positive response of oat as a second crop was obtained per kg of lupine-N added to the system when compared with the continuous oat–oat. The cereal also responded positively to mineral N in the legume amended soil in contrast with the oat–oat sequence where no response was observed, partly due to the fast mineralization rate of lupine residue and a greater soil N immobilization in the continuous oat system. Each kg N ha−1 added to the soil through the application of 73 kg DM ha−1 mature lupine residue (above- and belowground material) increased by 72 kg DM ha−1 the oat biomass produced as the second crop in rotation when 150 kg mineral N ha−1 were split in the season, independent of tillage practice. Mature legume residue conserved in the no-tilled soil depressed the yield of succeeding cereal but less than the continuous oat–oat for both tillage practices, where the application of mineral N did not improve the crop response.  相似文献   

9.
High rates of nitrogen (N) fertilizer may increase N leaching with drainage, especially when there is no further crop response. It is often discussed whether leaching is affected only at levels that no longer give an economic return, or whether reducing fertilization below the economic optimum could reduce leaching further. To study nitrate leaching with different fertilizer N rates (0–135 kg N ha−1) and grain yield responses, field experiments in spring oats were conducted in 2007, 2008 and 2009 on loamy sand in south-west Sweden. Nitrate leaching was determined from nitrate concentrations in soil water sampled with ceramic suction cups and measured discharge at a nearby measuring station. The results showed that nitrate leaching per kg grain produced had its minimum around the economic optimum, here defined as the fertilization level where each extra kg of fertilizer N resulted in a 10 kg increase in grain yield (85% DM). There were no statistically significant differences in leaching between treatments fertilized below this level. However, N leaching was significantly elevated in some of the treatments with higher fertilization rates and the increase in nitrate leaching from increased N fertilization could be described with an exponential function. According to this function, the increase was <0.04 kg kg−1 fertilizer N at and below the economic optimum. Above this fertilization level, the nitrate leaching response gradually increased as the yield response ceased and the increase amounted to 0.1 and 0.5 kg kg−1 when the economic optimum was exceeded by 35 and 100 kg N ha−1, respectively. The economic optimum fertilization level depends on the price relationship between grain and fertilizer, which in Sweden can vary between 5:1 and 15:1. In other words, precision fertilization that provides no more or no less than a 10 kg increase in grain yield per kg extra N fertilizer can be optimal for both crop profitability and the environment. To predict this level already at fertilization is a great challenge, and it could be argued that rates should be kept down further to ensure that they are not exceeded due to overestimation of the optimum rate. However, the development of precision agriculture with new tools for prediction may reduce this risk.  相似文献   

10.
In organic agriculture, weeds and nitrogen deficiency are the main factors that limit crop production. The use of relay-intercropped forage legumes may be a way of providing ecological services such as weed control, increasing N availability in the cropping system thanks to N fixation, reducing N leaching and supplying nitrogen to the following crop. However, these ecological services can vary considerably depending on the growing conditions. The aim of this study was to identify early indicators to assess these two ecological services, thereby giving farmers time to adjust the management of both the cover crop and of the following crop.Nine field experiments were conducted over a period of three years. In each experiment, winter wheat was grown as sole crop or intercropped with one of two species of forage legumes; Trifolium repens L. or Trifolium pratense L. Two levels of fertilization were also tested (0 and 100 kg N ha−1). After the intercropping stage, the cover crop was maintained until the end of winter and then destroyed by plowing before maize was sown. Legume and weed biomass, nitrogen content and accumulation were monitored from legume sowing to cover destruction.Our results showed that a minimum threshold of about 2 t ha−1 biomass in the aboveground parts of the cover crop was needed to decrease weed infestation by 90% in early September and to ensure weed control up to December. The increase in nitrogen in the following maize crop was also correlated with the legume biomass in early September. The gain in nitrogen in maize (the following crop) was correlated with legume biomass in early September, with a minimum gain of 60 kg N ha−1 as soon as legume biomass reached more than 2 t ha−1.Legume biomass in early September thus appears to be a good indicator to predict weed control in December as well as the nitrogen released to the following crop. The indicator can be used by farmers as a management tool for both the cover crop and following cash crop. Early estimation of available nitrogen after the destruction of the forage legume can be used to adjust the supply of nitrogen fertilizer to the following crop.  相似文献   

11.
The sustainability of growing a maize—winter wheat double crop rotation in the North China Plain (NCP) has been questioned due to its high nitrogen (N) fertiliser use and low N use efficiency. This paper presents field data and evaluation and application of the soil–vegetation–atmosphere transfer model Daisy for estimating crop production and nitrate leaching from silty loam fields in the NCP. The main objectives were to: i) calibrate and validate Daisy for the NCP pedo-climate and field management conditions, and ii) use the calibrated model and the field data in a multi-response analyses to optimise the N fertiliser rate for maize and winter wheat under different field managements including straw incorporation.The model sensitivity analysis indicated that a few measurable crop parameters impact the simulated yield, while most of the studied topsoil parameters affect the simulated nitrate leaching. The model evaluation was overall satisfactory, with root mean squared residuals (RMSR) for simulated aboveground biomass and nitrogen content at harvest, monthly evapotranspiration, annual drainage and nitrate leaching out of the root zone of, respectively, 0.9 Mg ha−1, 20 kg N ha−1, 30 mm, 10 mm and 10 kg N ha−1 for the calibration, and 1.2 Mg ha−1, 26 kg N ha−1, 38 mm, 14 mm and 17 kg N ha−1 for the validation. The values of mean absolute deviation, model efficiency and determination coefficient were also overall satisfactory, except for soil water dynamics, where the model was often found erratic. Re-validation run showed that the calibrated Daisy model was able to simulate long-term dynamics of crop grain yield and topsoil carbon content in a silty loam field in the NCP well, with respective RMSR of 1.7 and 1.6 Mg ha−1. The analyses of the model and the field results showed that quadratic, Mitscherlich and linear-plateau statistical models may estimate different economic optimal N rates, underlining the importance of model choice for response analyses to avoid excess use of N fertiliser. The analyses further showed that an annual fertiliser rate of about 300 kg N ha−1 (100 for maize and 200 for wheat) for the double crop rotation with straw incorporation is the most optimal in balancing crop production and nitrate leaching under the studied conditions, given the soil replenishment with N from straw mineralisation, atmospheric deposition and residual fertiliser.This work provides a sound reference for determining N fertiliser rates that are agro-environmentally optimal for similar and other cropping systems and regions in China and extends the application of the Daisy model to the analyses of complex agro-ecosystems and management practices under semi-arid climate.  相似文献   

12.
The expansion of biogas production from anaerobic digestion in the Po Valley (Northern Italy) has stimulated the cultivation of dedicated biomass crops, and maize in particular. A mid-term experiment was carried out from 2006 to 2010 on a silt loamy soil in Northern Italy to compare water use and energy efficiency of maize and sorghum cultivation under rain fed and well-watered treatments and at two rates of nitrogen fertilization. The present work hypothesis were: (i) biomass sorghum, for its efficient use of water and nitrogen, could be a valuable alternative to maize for biogas production; (ii) reduction of irrigation level and (iii) application of low nitrogen fertilizer rate increase the efficiency of bioenergy production. Water treatments, a rain fed control (I0) and two irrigation levels (I1 and I2; only one in 2006 and 2009), were compared in a split–split plot design with four replicates. Two fertilizer rates were also tested: low (N1, 60 kg ha−1 of nitrogen; 0 kg ha−1 of nitrogen in 2010) and high (N2, 120 kg ha−1 of nitrogen; 100 kg ha−1 of nitrogen in 2010). Across treatments, sorghum produced more aboveground biomass than maize, respectively 21.6 Mg ha−1 and 16.8 Mg ha−1 (p < 0.01). In both species, biomass yield was lower in I0 than in I1 and I2 (p < 0.01), while I1 and I2 did differ significantly. Nitrogen level never affected biomass yield. Water use efficiency was generally higher in sorghum (52 kg ha−1 mm−1) than in maize (38 kg ha−1 mm−1); the significant interaction between crop and irrigation revealed that water use efficiency did not differ across water levels in sorghum, whereas it significantly increased from I0 and I1 to I2 in maize (p < 0.01). The potential methane production was similar in maize and sorghum, while it was significantly lower in I0 (16505 MJ ha−1) than in I1 and I2 (21700 MJ ha−1). The only significant effect of nitrogen fertilization was found in the calculation of energy efficiency (ratio of energy output and input) that was higher in N1 than in N2 (p < 0.01). These results support the hypothesis that (i) sorghum should be cultivated rather than maize to increase energy efficiency, (ii) irrigation level should replace up to 36% of ETr and (iii) nitrogen fertilizer rate should be minimized to maximize the efficiency in biomass production for anaerobic digestion in the Po Valley.  相似文献   

13.
Poor soil and drought stress are common in semiarid areas of China, but maize has a high demand for nitrogen (N) and water. Maize production using the technique of double ridges and furrows mulched with plastic film are being rapidly adopted due to significant increases in yield and water use efficiency (WUE) in these areas. This paper studied N use and water balance of maize crops under double ridges and furrows mulched with plastic-film systems in a semiarid environment over four growing seasons from 2007 to 2010. To improve precipitation storage in the non-growing season, the whole-year plastic-film mulching technique was used. There were six treatments which had 0, 70, 140, 280, 420 or 560 kg N ha−1 applied in every year for maize. In April 2011, spring wheat was planted in flat plots without fertilizer or mulch following four years of maize cultivation. After four years, all treatments not only maintained soil water balance in the 0–200 cm soil layer but soil water content also increased in the 0–160 cm soil layer compared to values before maize sowing in April 2007. However, under similar precipitation and only one season of spring wheat, soil water content in the 0–160 cm soil layer sharply decreased in all treatments compared to values before sowing in April 2011. Over the four years of maize cultivation, average yield in all treatments ranged from 4071 to 6676 kg ha−1 and WUE ranged from 18.2 to 28.2 kg ha−1 mm−1. In 2011, the yield of spring wheat in all treatments ranged from 763 to 1260 kg ha−1 and WUE from 3.5 to 6.5 kg ha−1 mm−1. The potential maximum grain yield for maize was 6784 kg ha−1 with 360 kg N ha−1 applied for four years, but considerable NO3N accumulated in the soil profile. A lesser application (110 kg N ha−1) to this tillage system yielded in 82% of the maximum, increased nitrogen use efficiency and mitigated the risk of nitrogen loss from the system. This study suggests that double ridge–furrow and whole-year plastic-film mulching could sustain high grain yields in maize with approximately 110 kg N ha−1 and maintain soil water balance when annual precipitation is >273 mm in this semiarid environment.  相似文献   

14.
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   

15.
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   

16.
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   

17.
To identify the best practice for nitrogen (N) fertilization of overwinter processing spinach, two field experiments were carried out in the Foggia plain (Southern Italy), one of the most vocated area for leafy vegetables production. The field trials were aimed to define and suggest the proper fertilizer dose, typology and the right time of application. Experiment 1 evaluated four N fertilizer doses (0, 150, 225, 300 kg ha−1) in a two-year field trial. Experiment 2 was aimed to assess the effect of the split distribution of prilled urea fertilizer in comparison with the application of nitrification inhibitor (DMPP) containing urea fertilizer, broadcasted at sowing.Spinach yield, yield quality (nitrate – NO3− – and carotenoids content), N-use efficiency and risk of soil nitrate (NO3−-N) leaching were evaluated. The processing spinach yielded 37.8 and 3.6 t ha−1 of fresh and dry yield, respectively (average of the two experiments). Fresh and dry yield among the fertilizing treatments were similar. Also the β-carotene and the lutein content of spinach leaves (19.5 and 38.1 mg kg−1, respectively) were not affected by the N fertilizer dose. Conversely, the N dose strongly influenced the NO3− content of the leafy vegetable tissues (1286 mg kg−1 on average, 58% lower than the limits imposed by the EC regulation). As expected, the different rainfall pattern influenced both the leaf NO3− content and the risk of soil NO3−-N leaching. The results achieved demonstrated that, in order to get a favorable trade-off, among yield, yield quality, N-use efficiency and environmental impact, the processing spinach growers of the Foggia plain area should be encouraged to apply 225 kg N ha−1 as maximum fertilization rate. Also, the split urea fertilizer application appeared as the more effective strategy for N fertilization of overwinter spinach in comparison with the use of the nitrification inhibitor containing urea fertilizer, being the last strategy not able to adequately match the N crop demand.  相似文献   

18.
The agricultural sector is highly affected by climate change and it is a source of greenhouse gases. Therefore it is in charge to reduce emissions. For a development of reduction strategies, origins of emissions have to be known. On the example of sugar beet, this study identifies the main sources and gives an overview of the variety of production systems. With data from farm surveys, calculations of greenhouse gas (GHG) emissions in sugar beet cultivation in Germany are presented. Emissions due to the production and use of fertilizers and pesticides, emissions due to tillage as well as field emissions were taken into account. All emissions related to the growing of catch crops during fall before the cultivation of sugar beet were also included. The emissions are related to the yield to express intensity.The median of total GHG emissions of sugar beet cultivation in Germany for the years 2010–2012 amounted to 2626 equivalents of CO2 (CO2eq) kg ha−1 year−1 when applying mineral plus organic fertilizer and to 1782 kg ha−1 when only organic fertilizer was applied. The CO2eq emissions resulting from N fertilization exclusively were 2.5 times higher than those caused by diesel and further production factors. The absence of emissions for the production of organic fertilizers led to 12% less total CO2eq emissions compared to the use of mineral fertilizer only. But by applying organic fertilizer only, there were more emissions via the use of diesel due to larger volumes transported (126 l diesel ha−1 vs. 116 l ha−1 by applying mineral fertilizer exclusively).As there exists no official agreement about calculating CO2eq emissions in crop production yet, the authors conclude that there is still need for further research and development with the aim to improve crop cultivation and crop rotations concerning GHG emissions and the therewith related intensity.  相似文献   

19.
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   

20.
The aim of the present work was to evaluate the effect of soil water availability and nitrogen fertilization on yield, water use efficiency and agronomic nitrogen use efficiency of giant reed (Arundo donax L.) over four-year field experiment.After the year of establishment, three levels for each factor were studied in the following three years: I0 (irrigation only during the year of establishment), I1 (50% ETm restitution) and I2 (100% ETm restitution); N0 (0 kg N ha−1), N1 (60 kg N ha−1) and N2 (120 kg N ha−1).Irrigation and nitrogen effects resulted significant for stem height and leaf area index (LAI) before senescence, while no differences were observed for stem density and LAI at harvest.Aboveground biomass dry matter (DM) yield increased following the year of establishment in all irrigation and N fertilization treatments. It was always the highest in I2N2 (18.3, 28.8 and 28.9 t DM ha−1 at second, third and fourth year growing season, respectively). The lowest values were observed in I0N0 (11.0, 13.4 and 12.9 t DM ha−1, respectively).Water use efficiency (WUE) was significantly higher in the most stressed irrigation treatment (I0), decreasing in the intermediate (I1) and further in the highest irrigation treatment (I2). N fertilization lead to greater values of WUE in all irrigation treatment.The effect of N fertilization on agronomic nitrogen use efficiency (NUE) was significant only at the first and second growing season.Giant reed was able to uptake water at 160–180 cm soil depth when irrigation was applied, while up to 140–160 cm under water stress condition.Giant reed appeared to be particularly suited to semi-arid Mediterranean environments, showing high yields even in absence of agro-input supply.  相似文献   

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