Recycling of crop residues for sustainable crop production in wheat-peanut rotation system

Transcription

1 Symposium no. 59 Paper no. 373 Presentation: poster Recycling of crop residues for sustainable crop production in wheat-peanut rotation system SAFWAT M.S.A. (1), SHERIF M.A. (2), ABDEL-BARY E.A. (3), SAAD O.A.O. (1) and El MOHANDES M.A. (4) (1) Department of Agric. Microbiology, Fac. of Agric., Minia Univ., Egypt (2) Department of Soil Science, Fac. of Agric., Minia Univ., Egypt (3) Department of Soil Science, Fac. of Agric., Zagazig Univ., Egypt (4) Dept.of Environment and Biological Agric., Fac. of Agric., Al-Azhar Univ.Egypt Abstract Field experiments were conducted in sandy soil of West-Samalout, Minia, Egypt, under the auspices of (FAO/IAEA), Vienna, Austria, from December 1996 to October The main objectives of these experiments are (i) to obtain long-term effects of applications of crop residues on crop nutrition, yields and soil fertility; (ii) improve process level understanding of nutrient flows through the use of isotopic techniques and (iii) to enhance the efficiency of using nutrients by wheat-peanut rotation system. The experiment consisted of four treatments: (i) T1-15 N labelled (NH 4 ) 2 SO 4, 60 kg N ha -1 at 9.82% 15 N with unlabelled residues; (ii) T2-15 N labelled wheat residues 26 kg N ha -1 at 1.94% 15 N a.e, applied at the end of the first season; (iii) T3 to generate unlabelled residues and yield and (iv) T4-15 N labelled (NH 4 ) 2 SO 4, 60 kg N ha -1 at 9.82% 15 N a.e., applied at the beginning of the first season, without residues. The Ndff recoveries during the first season in T1 and T4 treatments were 26.8% and 25.6% respectively, while 15 N remaining in soil was 24.6% and 24.5% for T1 and T4, respectively. Thus, the total 15 N accounted (in plant and soil) were 51.4% for T1 and 50.2% for T4. After the second crop, the total 15 N recovery was 24.9% and 13% for T1 and T4 treatments, respectively. The application of the crop residues seems to decrease the N losses from the soil. Recoveries of %Ndfr by wheat from the labelled residue (T2) were 1.0% and 0.4% during the seasons 3 and 5, respectively, while recoveries of %Ndfr by peanut from T2 treatments were 3.7, 4.1 and 0.3 during the seasons 2, 4 and 6 respectively. In the following five seasons (peanut-wheat-peanut-wheat-peanut) total 15 N recovery by plant and soil were 66.7, 52.5, 34.3, 24.9 and 16.4%, respectively. Keywords: isotope techniques, crop residues, nutrient turnover, sustainable agriculture Introduction In Egypt as one of the developing countries, both soil quality and productivity have declined as a result of the intensive agriculture rotation system, and hence organic matter amendments throughout the available organic residues can be used to enhance soil fertility, crop productiuon and agricultural sustainability. In general, due to the extensive cultivation processes, Egyptian soils are poor in their organic matter content. In newly reclaimed sandy soils, less than 1% organic matter was recorded. To meet future demands, the crop production area cultivated must increase by 50% in the next 25 years, which is possible only if soil and water resources and inputs are used more 373-1

2 efficiently. Consequently, there is more interest in utilizing soils of low marginal productivity for crop production. The total yield of agricultural residues in Egypt has been as much as 24 millions tons per year, which is equivalent to 120 million kg N, 130 millions kg P, and 1,300 million kg K. of the used crop residues in the field which not only enhanced the content of organic matter in soil and increased the crop production, but also decreased the total amounts of chemical fertilizer consumption, as well as the environmental concerns. Understanding how crop residues decompose and how the resulting released nutrients are recycled or lost is important for more efficient residue and fertilizer management practices. The decomposition rate and nutrient release from crop residues are influenced by a number of soils environmental and crop residue factors. Soil microorganisms play a major role in crop residue decomposition and the subsequent fate of the nutrients is derived from this process. The amount of N supplied to the crop from an organic input is dependent on the mineralization of plant unavailable organic forms, to plant available inorganic forms of N, ammonium and nitrate. Mineralization is a complex process dependent on many environmental factors, (Azam et al., 1993; Thomas and Asakwa, 1993). Isotopic studies using 15 N labelled plant materials have been useful in estimating crop N uptake from organic N inputs (Azam et al., 1985; Jenkinson et al., 1985; Kirchmann, 1990). The objective of this study is to understand the nitrogen dynamics after a single input of the nutrient into the soil (via fertilizer or via crop residues) and how soil N dynamics are affected by adding carbon to the soil, in the form of crop resiudues. Materials and Methods The experiments were conducted in sandy soil (newly reclaimed land in Minia Governorate, Egypt) at the Experimental Farm of Minia University during , and winter seasons (November-May) and the summer seasons (May-October) in the system of annual wheat-peanut rotation. Mean day and night temperatures were 22 o C and 10 o C in the winter, and 43 o C and 20 o C in the summer, respectively. The relative humidity varied between 60% and 50% during winter and summer, respectively. Soil samples were collected from three depths (0-15, and cm). The collected samples were air dried and crushed to pass a 2-mm sieve. Physical and chemical analyses of soil samples are presented in Table 1. Soil moisture content, bulk density, total N, exchangeable NH 4, NO 3, extractable P and K, EC, CEC, ph, organic carbon were determined, according to the procedure (Page et al., 1982). Table 1 Initial physical and chemical soil characteristics in different depths (cm). Coarse sand % Fine sand % Silt % Clay % Texture Soil moisture % Bulk density (g/cm 3 ) ph CEC EC (ms/cm) sandy sandy sandy Organic matter Total nitrogen % Organic carbon % C/N ratio Available P (ppm) Available K (ppm) Available NH 4 (ppm) Available NO 3 (ppm) Biomass N (µg/g) Biomass C (µg/g)

3 Experimental design was a randomized complete block with 4 treatments, replicated 4 times. Individual plot size was 8x20 m (160 m 2 ) with a 15 N micro plot of 4x4 m (16 m 2 ). The experiment consisted of four treatments: (i) T1-15 N labelled (NH 4 ) 2 SO 4, 60 kg N ha -1 at 9.82% 15 N with unlabelled residues; (ii) T 2-15 N labelled wheat residues 26 kg N ha -1 at 1.94% 15 N a.e, applied at the end of the first season; (iii) T3 to generate unlabelled residues and yield and (iv) T4-15 N labelled (NH 4 ) 2 SO 4, 60 kg N ha -1 at 9.82% 15 N a.e., applied at the beginning of the first season, without residues. Wheat seeds (Triticum aestivum L.) var. Seds-1 and/or Beni Suef-6 and (Arachis hypogeae L) var. Giza-5 were used. During the first year, at seeding of the growing season 1 of wheat, micro plots of T1 and T4 were amended with 15 N at a rate of 60 kg N ha -1 (9.82% atom excess equivalent 5.89 kg 15 N ha). 15 N fertilizer (as ammonium sulphate) was split into four applications on T1 and T4 as follows: 25% at time of seeding, 25% 2 weeks after seeding, 25% 4 weeks after seeding and the last dose 6 weeks after seeding. Plots of T1-T4 received 60 kg N ha -1 as unlabelled ammonium sulphate. At the harvest of the growing season 1, 5 kg of labelled wheat straw (1.94% atom excess with 1.14% N) from micro plot of T1 was applied (5 kg plot -1 equivalent to 3,125 kg ha -1 or N kg ha -1 ) to micro plot of T2 after land preparation. Unlabelled wheat straw from plot T3 was applied at the same rate to micro plot of T1. Micro plot of T4 without addition labelled or unlabelled wheat straw was also included. Growing season 2, peanut seeds were inoculated before sowing with Bradyrhizobium that were grown on yeast extract mannitol (YEM) broth Medium 79 described by Allen (1959) for 6 days incubation at 39 o C then cultivated with normal cultural practices that were conducted as recommended and practiced by farmers in the area. Fertilizers were applied for three years as ammonium sulphate (20.6% N), superphosphate (15.5% P 2 O 5 ) and potassium sulphate (48% K) at a rate of 192 kg N ha -1, 125,75 kg P ha -1 and 99.5 kg K ha -1, respectively, for wheat experiment and at a rate of 72 kg N ha -1, 87.5 kg P ha -1 and 99.5 kg K ha -1, respectively for peanut experiment.sprinkle irrigation system was used.in the winter season, wheat plants received an average of 4,560 m ha -1. In the summer season, peanut plants received an average of 7,915 m 3 ha -1. At the harvest, 15 N- labelled peanut residues from 15 N microplots of T1 and T2 were removed and replaced with unlabelled peanut residues from T3. 15 N-labelled peanut residues from 15 N microplots of T4 were removed without unlabelled peanut replacement. The same sequence was conducted in the following seasons 3, 4, 5, and 6 in the second and third years. From the wheat-peanut rotation for three years, soil and plant samples were collected every season for peanut or wheat. Percentage of N-derived from fertilizer %Ndff, wheat residue %Ndfr, total 15 N recovery % in soil, plant and losses, were calculated according to the equations by IAEA (1990). Total N and 15 N in Plant and soil samples were analyzed at IAEA Soil Laboratory,Vienna,Austria. Data were statistically analyzed by the computer SAS package. Results and Discussion Total wheat and peanut yield (kg ha -1 ) for 6 seasons In the first year, growing season 1 of wheat crop, only T1 and T4 received 15 N in their microplots. The data obtained from both are represented in Figure 1. The total yield was 5, and 5, (kg ha -1 ) for T1 and T4, respectively. There was no 373-3

4 significant difference in the wheat yield among T1 and T4 in the first season, where they had received the same rate of Nitrogen fertilizer (60 kg N ha -1 ) and % N). In Year 1, growing season 2, the total peanut yield kg ha -1 recorded almost identical yield and there was no significance among T1 ( ), T2 (626.88) and T4 ( ). High values were recorded in treatment T4 as compared with the treatments T1 and T2, but still they were not significant. This may be due to the wide C/N ratrio of wheat straw and a slow decomposition of wheat straw that is affected the nutrient availability for plant growth. In Year 2, growing season 3, high total yield of wheat (kg ha -1 ) was obtained from T1 (6662.5) followed by T2 ( ) and T4 ( ) in Figure 1. This may be due to the decomposition of peanut residues with narrow C/N ration in both T1 and T2 as compared with T4 without residues of peanut. In Year 2,growing season 4, after 2 years and 4 growing seasons, the highest yield kg ha -1 peanut was obtained from T2 (737.5), followed by T4 (4491.8) and T1 (4192.5). In general, the total yield of peanut was lower as compared to the first year, growing season 2. This may be due to extreme climatic conditions, especially the high temperature of 43 C during the summer growing season. In Year 3,growing season 5, the total wheat yield kg ha -1 was high in T2 (5,593.1) followed by T4 (4,890.6) and T1 (4,859.4). It is also worth mentioning that low values were generally recorded to damage the wheat grain which may be due to the attack of some birds before harvest time. In Year 3, growing season 6. The total peanut yield (kg ha -1 ) recorded high value in T2 (4,046.75) as compared with T1 (3,778.05) and T4 (3,720.25), this my be due to the positive effect of decomposition of plant residues and the availability of nutrients for peanut growth kg/ha T1 T2 T Season 1 Season 2 Season 3 Season 4 Season 5 Season 6 Figure 1 Total yield kg ha -1 of wheat and peanut for 6 seasons (wheat peanut rotation system) of treatments (T1, T2 and T4). Total nitrogen yield (kg ha -1 ) of wheat and peanut for 6 seasons Regarding Year 1, growing season 1, in the total N yield of wheat there was no significant difference among the treatments of T1 (75.41) and T4 (69.86) in (Figure 2). In Year 1, growing season 2, total N yield kg ha -1 of peanut, higher values were recorded in both treatments of T1 (124.9) and T4 (124.53) as compared with T2 (118.08). In Year 2, growing season 3,total N yield of wheat was obtained by T

5 (79.57), followed by T1 (78.57) and T2 (64.93). In Year 2, growing season 4, the total N yield of peanut was high in T2 (87.24) as compared with T1 (73.83) and T4 (73.41). During Year 3, growing season 5, the same trend prevailed, the total N yield of wheat recorded high values in T2 (84.87), followed by T1 (70), and the lowest values were obtained by T4 (60.64). In Year 3, growing season 6, regarding the total N yield of peanut as expected, the highest values were recorded in T2 (111.46), followed by T1 (99.4) and T4 (79.78). In most cases, in T1 and T2, highest values were obtained in both treatments where crop residues were added of wheat straw or peanut leaves, as compared with T4 (no crop residues added). This may be due to the release of nutrients from both crop residues of wheat or peanut as it has a favourable effect on the soil properties and plant growth.soil decomposing crop residues were added to the soil and nutrients present in the residues may be released to the soil and be further available to the crop.several factors affect the turnover processes involved,such as the residue quality, the population of decomposers, incorporation of crop residues,weather and soil attributes, among others. kg/ha Season 1 Season 2 Season 3 Season 4 Season 5 Season 6 T1 T2 T4 Figure 2 Total N-yield kg ha -1 of wheat and peanut for 6 seasons (wheat peanut rotation system) of treatments (T1, T2 and T4). Total 15 N recovery % in soil, plant and losses during 3 years of wheat-peanut rotation system In year 1, growing season 1, the total percent of 15 N recovery in soil was in T1 (24,605%) and in T4 (24.56%). As expected, there was no significant difference among the treatments. The same trend was observed in the total 15 N recovery of wheat, T1 (26.75%) and T4 (26.61%). Regarding the losses, the total 15 N recovery % in both treatments of T1 and T4 recorded similar values in T1 ((48.65%) and in T4 (49.82%) Figure 3. In Year 1, growing season 2, the total 15 N recovery in soil was in T1 (20.57%), high value in T2 (63.05%), and low value in T4 (8.58%). On the other hand, 373-5

6 low values of the total 15 N recovery of peanut were recorded in T1 (4.305), in T2 100% 90% Total 15 N recovery % 80% 70% 60% 50% 40% 30% 20% 10% 0% T1 T4 T1 T2 T4 T1 T2 T4 T1 T2 T4 T1 T2 T4 T1 T2 T4 Season 1 Season 2 Season 3 Season 4 Season 5 Season 6 Loss Plant Soil Figure 3 Total 15 N recovery % in soil, plant and losses for 6 seasons (wheat peanut rotation system) of treatments (T1, T2 and T4). (3.67%) and in T4 (4.38%). The total 15 N recovery losses were obtained in T1 (75.13%), T %) and in T4 (87.04%). In Year 2, growing season3, the total 15 N recovery in soil was low in both T1 (17.59%) and T4 (9.73%) but high value was recorded int2 (51.48%). The total 15 N recovery in wheat recorded very low values in all treatments under study, T1 (0.44%), T2 (0.99%) and T4 (0.485%). The total 15 N recovery losses recorded high values in both treatments T1 (81.97%) and T4 (89.79%) as compared with T2 (47.53%). In Year 2, growing season 4, the total 15 N recovery recorded high values in T2 (30.23%) as compared with low values in both T1 (12.41%) and T4 (7.095%). The total 15 N recovery in peanut was in T1 (2.67%), T2 (4.07%) and T4 (2.78%). On the other hand, the total losses of 15 N recovery were high in T1 (84.92%) and T4 (90.135%) as compared with T2 (65.7%). In Year 3, growing season 5,the total 15 N recovery in the soil was relatively low in all treatments T2 (24.50%), followed by T1 (11.30%) and T4 6.04%). The total 15 N recovery in peanut recorded very low values, T1 (0.09%).T2 (0.37%) and T4 (0.098%). As expected, the total 15 N recovery losses were high in T4 (93.58%), followed by T1 (88.61%) and in T2 (75.73%). In Year 3, growing season 6, the total 15 N recovery in soil was relatively low in T2 (16.06%), followed by T1 (12.215%) and by T4 (6.58%). Low values were also obtained in the total plant part of wheat T1 (0.8%), T2 (0.31%) and T4 (0.47%). As expected, high total 15 N recovery losses were recorded in T4 (92.95%), T1 (86.47%) and T2 (83.63%). 6 cropping seasons after an application of labelled fertilizer, N recovery in the crop-soil system. ranged from 7 to 51% of the fertilizer N applied (losses varied between 16 and 66% of the fertilizer N applied ), when crop residues were added, and from 39 to 49% (losses between 33 and 88%), when no crop residues 373-6

7 were added. Fertilizer N applied to a crop may follow several paths. It may be taken up by the crop and subsequently removed in the harvested part, or returned to the soil in crop residues. Another possibility is that part of the N may be lost from the crop-soil system by a variety of processes, including nitrate leaching, denitrification, and ammonia volatilization. The applied N may also be retained in soil, in plant roots or through immobilization into the soil microbial biomass and subsequent transformations into other organic forms. The use of 15 N may underestimate N recovery rates due to a dillution effect, since the N pool in soil is much larger than the amount of 15 N applied as a tracer for fertilizer N, Jenkinson et al. (1985), which may explain the results. Other probable reasons should be further studied. When N is applied via crop residues treatment (T2), it behaves in a very different manner. Retention in soil is much greater than when N is applied via inorganic fertilizers but the recovery in the crop-soil system is poor due to a very low uptake rate by the crop. There should probably be a lack of synchronization between N release from the residues and N demand by the crop. Nitrogen recovery during 3 years of wheat-peanut rotation system During the seasons of growing wheat-peanut system, it is clear that the addition of wheat and peanut residues has a beneficial effect on the growth in accordance of their organic matter and nitrogen content especially for peanut as a legume plant. The addition of residues causes more efficient N recovery than in the case without application (Figure 4). Nitrogen recovery was higher in the beginning seasons and it decreased after that (Figure 5). This is because the N contained in legume residues is only partially available to plants during the first growing season and the beneficial effect of these residues is due largely to the fact that they increase the long-term fertility of the soil, (Ladd et al., 1981). Several investigations have reported that the burying in soil of low nitrogen residues improves N mineralization, (Ladd, 1981; Azam et al., 1985; Smith and Sharpley, 1990). The results of these experiments support this trend. Residues management appears to be very important for maintaining and improving soil structure. This result was also consistent with Wani and Shinde (1980), who reported that the incorporation of wheat straw favors the growth of groundnut and gives higher yields of wheat as a successive crop. Conclusions In the newly reclaimed sandy soil, which is poor in organic matter (0.11% OM) and low in nitrogen content (0.014%), wheat straw and peanut leaves (as residues) maintain continuous N supply in the soil during most of the growing period of the wheat-peanut rotation system and can be utilized as a source of N for wheat-peanut production in such sandy soil. It appears that wheat straw and peanut leaves as N source have very little utility, especially during the seasons of application. The present investigation also shows that incorporation of organic materials improved soil fertility and hence increased the yields of wheat and peanut during the years of cultivation. Acknowledgement The authors would like to express their sincere gratitude to the FAO/IAEA, Vienna, Austria for the support rendered to the project on The use of isotope technique in the studies on the management of organic matter and nutrient turnover for increasing sustainable agricultural production and environmental preservation CRP/EGY

8 N recovery, % Loss Plant Soil 0 +R -R +R -R +R -R +R -R +R -R season 2 Wheat season 3 season 4 Wheat season 5 season 6 Figure 4 Effect of incoporation of crop residues (+R = with residues; -R = without residues) on the recovery of mineral 15 N. 100% 15 N recovery, % 80% 60% 40% 20% Loss Plant Soil 0% season Wheat season 3 season 4 Wheat season 5 season 6 Figure 5 Effect of incoporation of lablled crop residues on the recovery of 15 N

9 References Allen, O.N Experiments in Soil Bacteriology. Burgess Publ. Co. Minneapolis, USA. 69 p. Azam, F., K.A. Malik and M.I. Sajjad Transformation in soil and availability to plants of 15 N applied as in organic and legume residues. Plant and Soil 86:3-13. Azam, F., F.W. Simmons, R. L. Mulvaney Mineralization of N from plant residues and its interaction with native soil N. Soil Biol. Biochem. Acta. 78:1-62. International Atomic Energy Agency Use of Nuclear Technologies in Studies of Soil Plant Relationships-Series 2, IAEA Laboratories, Seibersdorf, Vienna, Austria. Jenkinson, D.S., R.H. Fox and J.H. Rayner Interactions between fertilizer nitrogen and soil nitrogen the so-called priming effect. J. Soil Sci. 35: Kirchmann, H Nitrogen interactions and crop uptake from fresh and composted 15 N labelled poultry manure. J. Soil Sci. 41: Ladd, J.N The use of 15 N in following organic matter turnover with specific reference to rotation system. Plant and Soil 58: Page, A.L., R.H. Miller and D.R. Heeney Methods of Soil Analysis: II. Chemical and Microbiological Properties (2 nd ed.). Madison, Wisconsin, USA. Smith, S.J. and A.N. Sharpley Soil nitrogen mineralization in the presence of surface and incorporated crop residues. Agron. J. 82: Thomas, R.J. and N.M. Asakwa Decomposition of leaf from tropical forage grasses and legumes. Soil Biol. Biochem. 24: Wani, S.P. and P.A. Shinde Studies on biological decomposition of wheat straw: IV. incorporation of wheat straw and its microbial decomposers on yield of groundnut followed by wheat. Plant and Soil 55: