Effect of Tillage , Residue Management and Cropping System on the Properties of Soil

A field experiment was conducted to evaluate the effect of tillage practices, residue management and cropping system on soil properties at NMRP, Rampur, Chitwan from November 2015 to April 2016. The experiment was laid on Strip split design with combination of 12 different treatments i.e, zero tillage & conventional tillage as main plot in the strip, residue retention & residue removal as sub-plot factor and maize – wheat, maize + soybean – wheat & soybean – wheat cropping system as subsub plot factor. Three replications of the treatments were made. Soil sample before experiment and after harvest of wheat was taken (0-15cm). The experiment showed significant effect of zero tillage on organic carbon (2.169%) and on total soil nitrogen (0.112 %). Zero tillage with retention of residues is valuable tool for the conservation agriculture and helps in sustainability of soil however long-term research for the tillage management and residue retention should be conducted to highlight the major effects on change in properties of soil.


Introduction
Sustainable agriculture simply implies farming with wisdom.In sustainable farming, no any serious damage is caused to the soil, plant, environment, water bodies, human beings and animals.A profitable farm producing high quality of food in adequate amount, protecting its resources being environmentally safe and independent to purchasing of materials such as fertilizers is said to be sustainable.Sustainable farm relies much on the renewable resources drawn from the farm itself (Papendick & Parr, 1990).erosion (Wolkowski, 1996).Aim of tillage is to create soil environment favorable for plant growth (Klute, 1982).
Different tillage system and tillage intensity has different effect on soil physical, chemical and biological properties of soil (Ishaq et al., 2002).The contradictory results on soil properties as effect of different tillage system 'may be due to differences in crop species, soil properties, climatic characteristics and their complex interactions (Ishaq et al., 2002).Thus, study on effect of tillage on soil properties should be done for long-term so that more accurate generalizations can be made regarding the conditions required for sustainable tillage systems (Ishaq et al., 2002).Therefore, it is necessary to examine the long-term effects of tillage at different locations and under various environmental and soil conditions so that more accurate generalizations can be made regarding the conditions required for sustainable tillage systems (Ishaq, et al., 2002).
Minimum tillage generally coincides with the retention of crop residues, and it can play major role in improving the sustainability of cropping.Crop residues act as a sink and source for the plant nutrients (Hubbard & Jordan, 1996).Different crop residues have different capacity to serve as sink and source of nutrients for crop yield depends largely on climatic conditions, soil properties, crop characteristics and tillage practices (Doran & Smith, 1991).

Layout and Experimental Design
The field layout was done in strip split plot design with altogether of 12 treatments and 3 replications.The treatment includes, types of tillage system as main plot (a.zero tillage & b. conventional tillage), residue retention as sub plot (a. residue kept & b. residue removed) and cropping system as sub-sub plot (a.maize, b. soybean & c. maize + soybean).
The individual plot size was 6 m x4 m (24m 2 ).There was 0.5 m space between two plots and the distance of 1 m was maintained at each replication.The row spacing was maintained at 20 cm with continuous sowing in the row consisting of 30 rows in each plot.There were three destructive rows for taking plant samples for growth analysis.Further, one row was kept as a guard row between net plot and destructive rows from both sides.Outermost two rows of both sides of each plot were used as guard row.

Field Management Practices
The wheat variety Vijay was used as test crop for the research purpose, and the standard seed rate of 120 kg ha -1 was used.In conventional tillage strip, the field was plowed twice using the tractor drawn cultivator, double passing each time up to depth of 20 cm.Seed and basal fertilizers were separately applied in rows manually in the conventional tillage strip.In zero tillage strip, the field was sprayed with glyphosate 47% SL before 10 days of sowing with the rate of 10 ml per liter.Wheat seed and fertilizer was drilled at depth of 3 cm by a using tractor drawn inclined plate zero-till drill.
All the plots were fertilized using same level of nitrogen, phosphorous, and potassium.Nitrogen (N) was applied @ 100 kg ha -1 , Phosphorus (P2O5) @ 50 kg ha -1 and potassium (K2O) @ 50 kg ha -1 was applied in rows.Half dose of Phosphorous and potassium and only half dose of the nitrogen was applied at the time of sowing.Remaining nitrogen was applied in two equal splits as top dressings.

Chemical Properties of Soil before Experiment
The result of the chemical properties of soil is presented in Table 2.The Table shows the data on pH of soil, total nitrogen (%), available phosphorous, available potash and organic carbon (%).
Before experiment, all the soil chemical properties were found to be non-significant to each individual treatment.This is due to short term trial.This result was also similar to the research of (Comia, Stenberg, Nelson, Rydberg, & HaÊkansson, 1994).However, the highest soil pH (4.375) was recorded in maize + soybeanwheat cropping system and the least soil pH (4.275) was recorded in soybean-wheat cropping system.Total nitrogen (0.081%), available phosphorous (61 kg ha -1 ) and organic carbon (1.691%) was observed to be highest in no tillage methods and they were observed to be least in conventional tillage methods.Highest available potassium (257.645kg ha -1 ) was recorded in plot kept with residue and least was recorded in the plot where there was no retention of residue.No any other interaction effects were observed in between different treatments.Average soil pH, total nitrogen (in percentage), available phosphorous, available potassium and organic carbon (in percentage) was calculated to be 4.331, 0.074%, 59.491 kg ha -1 , 277.453 kg ha -1 and 1.493 % respectively.Fig. 1: Total nitrogen % in soil was influenced by interaction of (A) tillage methods and cropping system, and available phosphorous (kg ha -1 ) in soil was influenced by interaction of (B) residue management and cropping system at Rampur, Chitwan, Nepal during winter season of 2015/16 B. Thapa et al. (2018) Int. J. Appl. Sci. Biotechnol. Vol 6(2): 164-168 This paper can be downloaded online at http://ijasbt.org&http://nepjol.info/index.php/IJASBTInteraction effect between tillage and cropping system was observed for total nitrogen (%) in the experiment.Significantly higher LAI was observed in maize-wheat cropping system (under no tillage) which was statistically at par with soybean-wheat cropping system (under no tillage).The opposite effect was observed under conventional tillage (Fig. 1A).
For available phosphorous, interaction effect was observed between, residue and cropping system.Under both the residue management, available phosphorous was observed to be significantly higher in soybean-wheat cropping system, which was statistically at par with maize + soybean -wheat in residue kept plot and, it was also statistically at par with maize-wheat cropping system under residue removed plot (Fig. 1B).

Chemical Properties of Soil after harvesting of wheat
Result of chemical properties of soil is illustrated in Table 3.After harvest of wheat, chemical properties of soil, only total nitrogen percentage and organic carbon was found to be significant to tillage and rest of the other were nonsignificant.Total nitrogen was found to be significantly different in regard to tillage practice with significantly higher total nitrogen percentage being available in no till plot (0.112%) to conventionally tilled plot (0.093%).Soil nitrogen availability might have been influenced by tillage system due to its impact on soil organic carbon and nitrogen mineralization and subsequent plant nitrogen use or accumulation (Al-Kaisi & Licht, 2004).Likewise, organic carbon was significantly higher in no tilled plot (2.169%) in comparison to conventionally tilled plot (1.862%).Retention of residue leads to slow decomposition of the residues on the surface and increased organic carbon and total nitrogen in the top 5-15 cm of the soil but, this was not observed in the experiment as, the residue might not have decomposed in the given time frame.
Though other soil chemical properties were found to be non-significant, after harvest, higher pH was observed in plot with maize-wheat cropping system (4.733),higher available potassium was found in no plot with maize + soybeanwheat cropping system (243.735kg ha -1 ).This might be as a result of decarboxylation of organic anions on decomposition by microorganisms in undisturbed soil.But in long-term experiments (6±18 years) a decrease in the pH by 0.2± 0.3 pH-units in the topsoil (0±5 cm) was found after shallow tillage (Rasmussen, 1988).In contrast, higher available phosphorus was found in conventionally tilled plot (86.633 kg ha -1 ).B. Thapa et al. (2018) Int. J. Appl. Sci. Biotechnol. Vol 6(2): 164-168 This paper can be downloaded online at http://ijasbt.org&http://nepjol.info/index.php/IJASBTOnly soil pH was found to have interactive effect by management of crop residue and cropping system.There were no significant differences in the pH level in regard to either of cropping system for residue removed plot whereas, the plot managed with maize-soybean-wheat cropping system in residue retained plot were found to be significantly lower to rest of the plots in experiments (Fig. 2).

Fig. 2 :
Fig. 2: Soil pH after harvest of wheat was influenced by interaction of (A) residue management and cropping system at Rampur, Chitwan, Nepal during winter season of 2015/16 [Note: Mean separated by DMRT, and bar column represented with same letter (s) are non-significant at 0.05 level of significance.]

Table 1 :
Details of the treatments detail in a single replication with symbol

Table 2 :
Effects of tillage methods, residue management and cropping system on soil chemical properties before Note: Mean separated by DMRT and column represented with same letter(s) are non-significant at 0.05 level of significance.

Table 3 :
Effects of tillage methods, residue management and cropping system on soil chemical properties after experimentation at Rampur, Chitwan, Nepal during winter season of 2015/16 Note: Mean separated by DMRT and column represents with same letter(s) are non-significant at 0.05 level of significance.