Effect of Tillage, Residue and Fertilizer on Yields within a Wheat-Maize Cropping System
Effect of Tillage, Residue and Fertilizer on Yields within a Wheat-Maize Cropping System
Aqila Shaheen* and Nadia Sabir
Department of Soil and Environmental Sciences, The University of Poonch, Rawalakot Azad Jammu and Kashmir-Pakistan.
Abstract | The field study was carried out to determine the effect of tillage with and without residues and organic and inorganic fertilizers on yield of wheat-maize cropping systems in the erosion-vulnerable sub-humid area. Treatments included tillage levels i.e. ST (shallow tillage), STR (shallow tillage with residues), DT (deep tillage) and DTR (deep tillage with residues). Sub plots had three fertilizer’s levels viz. F1 (control), F2 (inorganic fertilizers) and F3 (farm yard manure; FYM+ inorganic fertilizers). Deep tillage increased wheat yield by 60%, 37% and 29% over ST, STR and DTR, respectively. F2 and F3 increased grain and straw yield compare to F1. In the case of maize, DT increased grain yield by 53%, 20% and 15%, over ST, STR and DTR, respectively. Deep tillage showed statistically higher water use efficiency (WUE) of 4.56 kg ha-1 mm-1 and 4.02 kg ha-1 mm-1 for both wheat and maize, respectively. However, similar WUE of wheat and maize was recorded for F2 and F3. Soil nitrogen, phosphorus and potassium after wheat-maize cropping rotations significantly responded to tillage, residues and organic and inorganic fertilizers. These results suggest that deep tillage has the potential to increase crop yield and WUE of wheat-maize cropping system in mountainous and sub-humid conditions.
Received | July 12, 2016; Accepted | February 17, 2017; Published | March 09, 2017
*Correspondence | SAqila Shaheen, Department of Soil and Environmental Sciences, The University of Poonch, Rawalakot Azad Jammu and Kashmir-Pakistan; Email: firstname.lastname@example.org
Citation | Shaheen, A. and N. Sabir. 2017. Effect of tillage, residue and fertilizer on yields within a wheat-maize cropping system. Sarhad Journal of Agriculture. 33(1): 127-138.
Keywords | Farm yard manure, Residues incorporation, Tillage practices, Wheat-maize
Eroded areas have lower yield due to climatic factors, land configuration and faulty conventional soil and crop management practices. The erratic and higher intensity rain, gentle to steep slopes and the lower addition of organic amendments cause less productivity. The mountainous topographic features in humid and sub-humid conditions result in higher runoff losses and low infiltration. Water erosion causes soil losses and nutrients removal with both runoff and sediments. It ultimately declines soil fertility, productivity, causes economic losses and environmental pollution (; ). The total amount, intensity and duration of rainfall, soil properties, land configuration, crops, soil and crop management practices determine the rate of erosion from agriculture farm lands (; ; ). The rate of erosion gets increase with low infiltration, crusting and compaction, less addition of crop residues ().
Among soil management practices crop residues incorporation has improved soil properties viz. biological, physical and chemical and conserved soil moisture and increased crop production (). Residues retention protects top soil and reduces soil nutrient losses (). Numerous studies (, , ; ; ; ) have shown higher maize yield with crop residues maintenance in soil. Crop residues incorporation increase SOM, soil N, P and K (). However, the effects of tillage vary according to different soil type and properties, cropping sequence, residue addition and climate. Few studies (; ) illustrated that tillage causes SOM decomposition and accelerates OM degradation which results less OM build up in soil. The additions of crop residues in soil at the sowing time mostly immobilize the inorganic nitrogen (). However, this can be reduced with incorporation of nitrogen as starter dose along with straw incorporation (). Tillage also affects soil water content by affecting surface runoff, infiltration rate and evaporation ().
The water use efficiency (WUE) of eroded areas also increases with available water contents and nutrients. The use of organic amendments (including farmyard manure (FYM) not only supply nutrients but also improves soil properties and conserves soil water (; ; ; ). The integrated application of FYM with inorganic fertilizers has increased wheat and maize yield (; ). Similarly, straw incorporation with organic manure has improved soil physical properties and increased wheat yield (; ). Studies (; and ) have shown higher crop productivity with the integrated addition of organic and inorganic amendments.
Due to global change in rainfall pattern, the humid areas having uncertain conditions of rainfall and winter rains are becoming less during the wheat germination period. For efficient utilization of rain water focus on more infiltration and less runoff is required. Research on tillage system is necessary to lessen land degradation and to get potential crop yields as average yield production of wheat-maize in mountainous, erosion-vulnerable areas region of Rawalakot (Latitude 33◦ 51’ to 33◦ 85’ N and longitude 73◦ 48’ to 73◦ 80’ E) Azad Kashmir-Pakistan is 1 Mg ha-1 to 1.5 Mg ha-1.
Wheat and maize are major cereal crops of the state of Azad Jammu and Kashmir-Pakistan and studies have not been conducted so far on tillage practices of wheat-maize cropping system. Due to the importance of wheat and maize crop for nation’s economy, lack of research on soil management and conservation practices, a study was conducted to determine (i) whether higher grain yield and water use efficiency due to deep tillage with and without residue incorporation is greater than shallow tillage with and without crop residues incorporation (ii) Response of crop yield and WUE to organic and inorganic fertilizers.
Materials and Methods
The field experiment of wheat-maize cropping system was carried out in 2009 and 2010 on clay loam soil at experimental research fields, Faculty of Agriculture, Univeristy of Poonch, Azad Jammu and Kashmir- Pakistan. The average annual precipitation of study area (Latitude 33◦ 51’ to 33◦ 85’ N and longitude 73◦ 48’ to 73◦ 80’ E) is 1481 mm; 33% rainfall is received in winter (Dec. to March), and parent material is residuium-colluvium from shales. Mean winter soil temperature is 15◦C. The monthly rainfall and temperature (minimum and maximum) during wheat and maize growing period is given in .
Description of field operations and treatments
The pre-sowing composite soil samples were collected for characterization of study area. The properties of experimental area are given in . The experimental plot was ploughed thoroughly twice by tractor and according to tillage depth field was tilled. The experiment lay out was split plot arranged in randomized complete block design with three replications. The treatments of main plots consists of: shallow tillage (0-15 cm; ST), shallow tillage with wheat straw incorporation @ 4 Mg ha-1 (STR), Deep tillage (0-30 cm; DT) and deep tillage with wheat straw incorporation @ 4 Mg ha-1 (DTR). The sub-plots were having three fertilizers levels viz. F1: Control (no application of fertilizers), F2: Recommended rate of fertilizer application (120 kg N, 60 kg P2O5 and 90 kg K2O per hectare) and F3: integrated application of inorganic and organic fertilizers (8 Mg farm yard manure (it provided 60 kg N, 60 kg P2O5 and 90 kg K2O per hectare). The fertilizers urea, diammonium phosphate (DAP) and sulphate of potash (SOP) were applied as source of nitrogen, phosphorus and potassium, respectively. All inorganic fertilizers were broadcasted at sowing and half nitrogen was applied at sowing and half after germination. The FYM was collected from neighboring house’s pens and its analysis showed total nitrogen percent was 0.78%. FYM was mixed thoroughly and spread evenly and applied to the experimental plots at sowing. Wheat straw in specified treatments according to layout plan was incorporated and properly mixed up to 15 cm depth at the time of sowing.
Wheat and maize as test crops were sown in winter and summer, respectively in rotation. Wheat (Triticum aestivum L.) variety “Saher” was sown on October 25, 2009 and harvested on May 20, 2011. Maize (Zea mays L.) variety “Sarhad white” was sown on June 24, 2010 and harvested on October 18, 2010. All cultural practices were adopted during whole growing period of crop.
Threshing was done manually and yield data was recorded at 12% water contents after harvesting middle rows of each plot. Leaf area (LA) measurements were taken at the flowering stage in wheat and at silking stage in maize.
|Bulk density||g cm-3||1.15||1.3|
|Volumetric water contents||mm||22.43||33.9|
|Textural class||-||clay loam||sandy loam|
|Phosphorus (extractable)||mg kg-1||10.8||8.9|
|Potassium (⸗)||mg kg-1||74||86|
|Copper (⸗)||mg kg-1||0.71||0.77|
|Iron (⸗)||mg kg-1||2.3||1.9|
|Manganese (⸗)||mg kg-1||3.571||4.616|
|Zinc (⸗)||mg kg-1||1.344||1.372|
Water use efficiency was computes as:
Total water supplied = water at sowing – water at harvesting + growing season precipitation
The harvest index was computed as:
The composite pre-sowing soil samples and post-harvest soil samples from every treatment were collected from 0-15 cm and 15–30 cm soil depth. Soil samples were air dried and processed by grinding in pestle and mortar and sieved with 2 mm sieve. The analyses for texture, pH1:2, EC1:10, OM, CaCO3, total N, P, K, Cu, Fe, Mn and Zn were done. Soil texture was determined by Bouyoucos hydrometer method (). Soil pH was measured saturated 1:2 of soil water suspension using pH meter (). Electrical conductivity was measured by preparing 1:10
Straw / Stover yield
Water use efficiency
(kg ha-1 mm-1)
|Tillage practices (T)|
|ST||1.79 c||2.0 b||3.99 ns||4.75 ns||0.33 ns||28.20 ns||26 c||5386.7 b||2.79 b||2.55 b|
|2.08 bc||2.55 ab||3.76||5.36||0.37||32.40||29 bc||5619 b||3.31 b||
|DT||2.86 a||3.06 a||5.10||5.59||0.34||35.96||34 ab||6093 a||4.56 a||4.02 a|
|2.21 b||2.67 a||4.23||6.22||0.34||29.41||36 a||6064 a||3.45 b||3.51 a|
|Fertilizers levels (F)|
|F1||1.64 b||1.22 b||2.68 b||3.92 b||0.37 ns||24.97 b||27 b||4717 c||2.57 b||1.60 b|
|F2||2.39 a||3.30 a||4.88 a||6.38 a||0.33||34.46 a||32 a||6521 a||3.78 a||4.33 a|
|F3||2.68 a||3.15 a||5.28 a||6.15 a||0.33||35.05 a||34 a||6134.8b||4.24 a||4.14 a|
ST: Shallow tillage 0-15 cm; STR: Shallow tillage with wheat straw residues @ 4 Mgha-1; DT: Deep tillage 1-30 cm; DTR: Deep tillage with wheat straw residues @ 8 Mgha-1; F1: No fertilizers application; F2: 120:90:60kg ha-1 NP2O5 K2O;F3: 60:90:60 kg ha-1 NP2O5 K2O + FYM @ 8 Mgha-1; NS/ns = non significant at P ≤ 0.05; Columns / rows sharing same letters are non-significant at P ≤ 0.05
soil suspension (soil and water) (). Soil OM was determined by a modified Mebius method (). Percent CaCO3 was determined by titration (). Total nitrogen in the soil was determined by Kjeldahl method (). Available P by method using spectrophotometer and extractable K by method using flame photometer. Micronutrients (Zn, Cu, Fe and Mn) soil extract was measured using atomic absorption spectrophotometer (). Soil water contents and bulk density were measured at sowing and after harvest by gravimetric () and core method () respectively, up to depth of 30 cm. The water contents were expressed as volumetric water contents by multiplying with bulk density.
The statistical analyses were done by MSTAT C software, treatment differences were calculated at the 5% probability by least significant difference (LSD) test.
Results and discussions
Yield, harvest index and leaf area of wheat
Tillage practices and fertilizers levels () showed statistically (p ≤ 0.05) significant effect on grain yield. Among tillage treatments; DT gave higher yield (2.86 Mg ha-1) while the lowest yield of 1.79 Mg ha-1 was found in ST. Deep tillage increases grain yield by 60%, 37% and 29% over ST, STR and DTR, respectively. Among fertilizers levels, F2 and F3 showed statistically (p ≤ 0.05) similar grain yield relative to the control (F1). The maximum higher straw yield was observed under DT that is statistically at par with DTR, STR and ST. However, percent increase of straw yield in DT over ST, STR and DTR was 28%, 36% and 21%, respectively. Among fertilizers levels, the trend of increase was similar as recorded for grain yield. Interactive effect of TxF was non-significant. Both tillage practices and fertilizers levels and their interactions showed statistically (p ≤ 0.05) similar harvest index (HI) values.
Leaf area response for both tillage and fertilizers practices () is statistically significant. Treatments DT and DTR showed significantly (p ≤ 0.05) higher LA than ST and STR. Both F2 and F3 showed significantly (p ≤ 0.05) higher LA than F1. Interaction of TxF was non-significant.
Yield, harvest index and leaf area of maize
Tillage and Integrated nutrient application practices significantly affected the grain yield of maize (). The significantly (p ≤ 0.05) higher grain yield (3.06 Mg ha-1) was found in DT and DTR (2.67 Mg ha-1) and the lowest of 2 Mg ha-1 in ST. DT showed 53%, 20% and 15% increase of grain yield over ST, STR and DTR, respectively. Integrated nutrient application practices also had statistically (p ≤ 0.05) significant impact on maize grain yield. The highest grain yield of 3.30 Mg ha-1 was recorded in F2 whereas in F3 it was 3.15 Mg ha-1 as compared to F1 (1.22 Mg ha-1) where no fertilizer was applied. The T×F interaction was non-significant (p ≤ 0.05). The effect of tillage treatments () on maize stover yield was non-significant. However, maximum yield of 6.22 Mg ha-1 was recorded in DTR and the lowest (4.75 Mg ha-1) in ST. Among fertilizers level inorganic nutrient alone or in integrated application with organic nutrients had significantly (p ≤ 0.05) higher stover yield than control. Higher stover yield of 6.38 Mg ha-1 and 6.15 Mg ha-1 was obtained in F2 and F3 treatments, respectively. The interaction of T×F was significant (p ≤ 0.05).
The tillage practices and integrated nutrient application had non-significant (p ≤ 0.05) effect on HI of maize (). The HI was 28.20% and 35.96% for ST and DT, respectively. Integrated nutrient application showed highly significant differences in HI. Maximum HI was recorded in F3 that was statistically at par with F2 while F1 gave a minimum HI. Interaction of tillage and fertilizers non-significantly (p ≤ 0.05) affected the HI.
The higher LA () was recorded in DT and DTR and minimum was in shallow tilled plots. Application of inorganic fertilizer and FYM in integration and separate had a statistically significant (p ≤ 0.05) effect on maize LA. The higher LA was recorded in F2 treatments followed by F3.
Water use efficiency of wheat and maize
shows that statistically higher (p ≤ 0.05) WUE of wheat was recorded for DT (4.56 kg ha-1 mm-1) and lower with ST (2.79 kg ha-1 mm-1). Deep tillage showed 63, 38 and 32% increase of WUE over ST, STR and DTR, respectively. Among fertilizers levels, F3 gave 4.24 kg ha-1 mm-1 WUE which is statistically higher than F1 (2.57 kg ha-1 mm-1) and similar to (p ≤ 0.05) F2 (3.78 kg ha-1 mm-1). Interaction of T×F WUE was statistically non-significant.
The WUE of maize significantly responded to tillage and fertilizers levels (). The higher WUE was recorded in DT (4.02 kg ha-1 mm-1) and DTR (3.51 kg ha-1 mm-1) and it was statistically similar with STR (3.35 kg ha-1 mm-1) and higher than (p ≤ 0.05) ST (2.55 kg ha-1 mm-1). The increase of WUE of DT over ST, STR and DTR was 58%, 20%, 15%, respectively. Application of inorganic and integrated nutrients has significant effect on the WUE and higher WUE was found in F2 (4.33 kg ha-1 mm-1) and it was followed by F3 (4.14 kg ha-1 mm-1). Interaction of T×F non-significantly affected WUE.
Soil characteristics after wheat-maize cropping system
Tillage system showed a significant impact on soil bulk density (BD) (). The higher BD was found in ST than other tillage systems. The lowest BD was found in DTR. Integrated nutrient application showed highly significant effect on the bulk density. The higher BD was in F1 and the lowest in F3 treatment. The TxF interaction significantly affected the BD at 15-30 cm depth but non-significantly at 0-15 cm depth at maize harvest.
Data of volumetric water contents is presented in . Tillage and fertilizer levels had statistically non-significant impact (p ≤ 0.05) on soil water at 0-15 and 15-30 cm depths. However, maximum water contents were found in DT and DTR than ST and STR. In integrated nutrient application the higher water contents were in F3 treatments. Interaction of TxF had non-significant effect on soil water contents at both depths.
Data pertaining to soil pH at 0-15 and 15-30 cm is given in . Statistically non-significant effect of tillage practices as well as fertilizers levels were found on soil pH at 0-15 and 15-30 cm soil depth. Interactive effect of TxF was statistically significant on soil pH.
Electrical conductivity of soil at depths 0-15 cm and 15-30 cm was statistically non-significant by tillage practices (). Integrated nutrient application effect on soil EC in surface plow layer was non-significant but had a significant effect on sub soil layer.
|Bulk Density (g cm-3)||Volumetric water Contents (mm)||Soil pH||Electrical Conductivity (dSm-1)||Calcium carbonate (%)||Organic matter (%)|
|0-15 cm||15-30 cm||0-15 cm||15-30 cm||0-15 cm||15-30 cm||0-15 cm||15-30 cm||0-15 cm||15-30 cm||0-15 cm||15-30 cm|
|Tillage practices (T)|
|ST||1.48 a||1.54 a||17.27 ns||17.22 ns||7.77 ns||7.86 ns||0.08 ns||0.08 ns||9.0 ns||8.92 ns||0.97 b||0.66 ns|
|1.44 ab||1.51 bc||17.37||17.316||7.89||7.95||0.08||0.08||9.25||9.25||1.23 a||0.73|
|DT||1.46 a||1.53 ab||17.63||18.05||7.91||7.89||0.08||0.08||10.2||10.21||1.21 a||0.68|
|1.39 b||1.49 c||18.29||17.37||7.80||7.99||0.07||0.07||10.61||10.61||1.00 b||0.70|
|Fertilizers levels (F)|
|F1||1.49 a||1.57 a||16.96 ns||17.58 ns||7.80 ns||7.93 ns||0.07 ns||0.07 b||9.37 b||8.92 b||0.99 b||0.60b|
|F2||1.44 b||1.51 b||17.37||17.33||7.83||7.92||0.08||0.08 ab||10.82 a||10.33 a||1.12 ab||0.69ab|
|F3||1.39 c||1.47 c||18.59||17.56||7.90||7.92||0.08||0.09 a||10.73 a||9.98 ab||1.20 a||0.78a|
ST: Shallow tillage 0-15 cm; STR: Shallow tillage with wheat straw residues @ 4 Mgha-1; DT: Deep tillage 1-30 cm; DTR: Deep tillage with wheat straw residues @ 8 Mgha-1; F1: no fertilizers application; F2: 120:90:60kg ha-1 NP2O5 K2O; F3: 60:90:60 kg ha-1 NP2O5 K2O + FYM @ 8 Mgha-1; NS/ns = non significant at P ≤ 0.05; Columns / rows sharing same letters are non-significant at P ≤ 0.05
The maximum EC was recorded in F3 which was statistically at par to F2. The small difference in EC of both soil depths was found and soil was free from salinity problem. Interaction of TxF was non-significant.
Data regarding CaCO3 are given in at both 0-15 and 15-30 cm depth. The CaCO3 did not show any statistical difference at both depths 0-15 and 15-30 cm to tillage types. Integrated nutrient application had statistically significant (p ≤ 0.05) impact on CaCO3 at both 0-15 and 15-30 cm depth. The higher CaCO3 contents were found in F2 at 0-15 cm and 15-30 cm depth. Interaction of TxF showed significant effect.
The tillage practices had a significant effect on OM in surface plow layer but had a non-significant effect on sub soil layer (). The highest OM (1.23%) was recorded for STR at surface plow layer and the same was at sub soil layer. Integrated nutrient application practices had a significant impact on OM at both 0-15 and 15-30 cm depth. The highest OM (1.20%) was found in F3 and it was statistically (p ≤ 0.05) at par with F2 at surface plow layer. Same trend was at sub soil layer. Interaction of TxF non-significantly affected the organic matter at both depths.
Soil Concentration of nutrients after wheat-maize harvest
Tillage systems did not have significant effect on soil N concentration (). However, the integrated nutrient application significantly (p ≤ 0.05) affected soil N concentration. The higher N was observed in F2 (0.07 %) at 0-15 cm depth and in F3 (0.06 %) at 15-30 cm soil depth. The TxF interaction had non-significant effect on N contents.
Soil phosphorous contents of different tillage practices were found statistically non-significant at both 0-15 and 15-30 cm depths. More soil P concentration (5.54 mg kg-1) was found at surface plow layer compared to sub soil layer. Integrated nutrient application showed significant (p ≤ 0.05) effect at both depths (0-15 and 15-30 cm) and maximum soil P concentration (5.88 mg kg-1) was found in F3 at 0-15 cm depth and F2 (4.91 mg kg-1) at sub soil layer (15-30 cm) as compared to F1. TxF interaction showed significant effect at both depths 0-15 and 15-30 cm.
Soil potassium contents were significantly affected by tillage practices at 0-15 and15-30 cm (). Maximum K contents (82.56 mg kg-1and 73.11 mg kg-1) were in ST than other tillage system at both depths (0-15 and 15-30 cm). The higher soil K concentration was found at 0-15 cm depth compared to that at subsoil (15-30 cm). Integrated nutrient application sig nificantly (p ≤ 0.05) affected K concentration at both depths (0-15 and 15-30 cm) and the maximum soil K contents (83.83 mg kg-1 and 76 mg kg-1) were found in F2 treatments at both depths (0-15 and 15-30 cm)
|Total N (%)||Phosphorus ( mg kg-1)||Potassium ( mg kg-1)|
|Treatments||0-15 cm||15-30 cm||0-15 cm||15-30 cm||0-15 cm||15-30 cm|
|Tillage practices (T)|
|82.56 a||73.11 a|
|0.06||0.06||5.39||4.40||78.56 b||72.78 a|
|DT||0.06||0.06||5.48||4.60||73.67 c||68.78 b|
|0.06||0.05||5.54||4.67||76.33 bc||72.00 a|
|Fertilizers levels (F)|
|F1||0.04 b||0.05 b||4.60 b||3.62 b||73.75 b||66.42 c|
|F2||0.07 a||0.05 b||5.81 a||4.91 a||83.83 a||
|F3||0.06 a||0.06 a||5.88 a||4.81 a||75.75 b||72.58 b|
ST: Shallow tillage 0-15 cm; STR: Shallow tillage with wheat straw residues @ 4 Mgha-1; DT: Deep tillage 1-30 cm; DTR: Deep tillage with wheat straw residues @ 8 Mgha-1; F1: no fertilizers application; F2: 120:90:60kg ha-1 NP2O5 K2O; F3: 60:90:60 kg ha-1 NP2O5 K2O + FYM @ 8 Mgha-1; NS/ns = Non significant at P ≤ 0.05; Columns / rows sharing same letters are non-significant at P ≤ 0.05
and lower in F1. Interaction of TxF also significantly affected K concentration at both depths (0-15 and 15-30 cm).
Residue incorporation with ST and DT did not show significant effect on crop yield that may be due to application of residues at the time of sowing i.e. residues had less time for decomposition altogether and nutrients of residues have not been into freely available form. Few studies had shown decreased grain yield of wheat due to crop residues incorporation because of poor seed germination (). Higher yield under DT compare to ST () could be due to less runoff and higher infiltration. Data of grain yield () suggests that integrated nutrient application was about as efficient as inorganic source of fertilizer. The combined use of FYM with inorganic fertilizers improve soil permeability, soil aggregates stability, checks N losses by organic mineral complexes and uptake of nutrients which in turn increase plant yield (). In long-term studies (; ) FYM @ 5 Mg ha-1 with 50% of the recommended rate of inorganic fertilizer has increased grain yield equivalent to 100% of the inorganic recommend rate of fertilizer. The results propose that integrated nutrient management can reduce 50 % usage of inorganic fertilizers. Earlier it was reported by that urea nitrogen + FYM in 75:25 ratios saved ≈25% (30 kg) of N fertilizer for wheat production.
In DT and DTR, the highest grain yield was obtained as compared to ST. It is attributed to the less soil compaction () and uniform distribution of soil nutrients (). and reported higher maize grain yield in deep tilled and conventional tillage practices than no tillage. The interaction of organic and inorganic sources and alone had higher grain yield than control. These results were in line with who demonstrated that the integrated application of FYM with NP fertilizers had similar maize grain as with recommended rate of inorganic fertilizers.
However, stover yield was statistically non-significant at all tillage treatments. Same results were found by . The higher stover yield with integrated management practices () might be due to availability of more nutrients that gave higher plant biomass and stover yield ().
Harvest index and leaf area of wheat and maize
Tillage practices had non-significant effect on wheat and maize harvest index (HI). reported significant effect of tillage on harvest index. Higher HI in application of inorganic source of nutrients and integrated organic and inorganic fertilizers application may be attributed to abundant root growth and higher water and nutrients uptake. It results in higher HI of maize crop ().
Plant LA had direct impact on carbohydrate manufacturing and transpiration process. The increase in LA in DT and F2 and F3 treatments is attributed to the readily available form of inorganic N and due to higher root proliferation and utilization of nutrients during growing season.
Wheat and maize water use efficiency
Higher WUE under DT may be due to disruption of hard layers or disruption of naturally occurring dense pans, which develops due to ploughing at same for long time (). Similarly, DTR had statistically similar WUE of maize as DT. Crop residue management, especially in sub-humid and semiarid regions, is to improve soil water conservation () due to reduced runoff due to improved soil structure that allows more infiltration. The more availability of water and nutrients in the root zone had a positive impact on WUE (). In our study lower WUE in ST might be due to less conservation of soil water and lower grain yield.
Soil characteristics after wheat-maize cropping system
Tillage and residue application affected soil water contents and BD variably. The non-significant water contents under tillage and fertilizers treatments may results because of irregular dry days and/or because of low residue rates under rain-fed conditions. The tillage practices affect soil water contents by affecting infiltration rate, surface runoff, evaporation losses and reducing the rain-drop impact (). Some studies however, showed a non-significant variance in soil water content of conservation and conventional tillage practices (). The study indicated the effect of tillage-residue practices on soil bulk density is variable as some scientists showed no effect (), whereas others reported lower soil bulk density () and residue incorporation (). In F1 higher bulk density may be due to higher re-settling of soil separates due to less growth and less canopy to cover surface from impact of rain drop. Soil pH and EC were unaffected by the treatments, however, EC is below 4 dSm-1 which shows no salinity problem in these soils. Lower CaCO3 in post- harvest compare to pre- sowing may be attributed to redistribution of CaCO3 in soil profile. Post-harvest organic matter was less compare to pre-sowing and this reduction is due to exhaustive effect of wheat-maize cropping system. Interactive effect of tillage practices with N fertilization (organic and inorganic) had higher SOC and both active carbon and nitrogen fraction (; ). The highest OM (1.23%) at surface plow layer and lowest (0.66%) at sub soil layer might be due to wheat residue incorporation on upper surface which showed higher OM at 0-15 cm depth ().
Concentration of nitrogen, phosphorus and potassium in soil after wheat-maize harvest
The N contents were statistically non-significant among tillage practices, however, lower N was found in ST. The initial crop growth was significantly reduced by reducing the tillage intensity (). The non-significant difference in total N contents in soil at maize harvest was also reported by . Overall negative balance of total nitrogen when compared with pre-sowing total nitrogen is attributed to exhaustive cropping system and fates of nitrogen losses. Higher N contents in F2 and F3 at 0-15 cm depth is due to higher application rate of N compare to F1. However, statistically similar N contents in F2 and F3 may be due to slow mineralization and less leaching of N in F3. The synergistic effect of N and organic fertilizers maintain higher soil total N (). The nitrogen fertilizers contribute 18-34 % soil residual N () and 4-9.4% further mineralization from soil total N ().
Tillage system showed no effect on P contents however, P concentration was higher in surface plow layer than sub soil layer (; ). The response of organic and inorganic sources alone and in combination showed the same response of higher P at 0-15 cm depth. The higher P content in F2 and F3 due to application of P compare to F1. The organic manures slowly releases nutrients and had higher residual effect than inorganic fertilizers (). reported a higher P availability due to increase in soil OM contents. However, overall soil phosphorous was low at maize harvest; this again might be due to exhaustive crops or P fixation.
Combination of FYM and NPK (a mineral fertilizer) had higher soil nutrient (N, P, K) contents (). The K contents were higher in upper 0-15 cm soil as than 15-30 cm depth. and after long experimentation of different tillage systems reported higher K concentrations in the surface layer than subsoil.
The higher yield was obtained with deep tillage than shallow tillage. Crop residues incorporation with shallow and deep tillage practices did not give higher yield as deep tillage without residues incorporation but showed higher yield than shallow tillage. Farm yard manure application as integrated approach with inorganic fertilizers gave comparable yield and of both wheat and maize as inorganic fertilizers application. Continuous plouging at same depth and removal of all crop residues reduces the yield of major cereals wheat and maize in wheat-maize cropping system.
Aqila Shaheen designed the research, did the statistical analysis and wrote the manuscript. Nadia Sabir continued maize study, analysed the soil and plant samples and recorded the yield.
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