ORGANIC MULCHING TO CONSERVE SOIL NUTRITIONAL QUALITY AND ENHANCE WHEAT YIELD

Nutritional degradation of soil is an alarming issue of present agriculture due to extensive farming to overcome food security. A field experiment was conducted during rabi season 2020-21 at the research area of Arid Zone Research Centre (AZRC), Dera Ismail Khan to assess the efficiency of two types of mulches (farm manure (FM) and wheat straw (WS) to conserve soil nutrient capacity with improving wheat yield. Wheat variety “AARI-2011” was sown @ 150 kg/ ha and fertilizers were applied @ 120-90-60 kg ha -1 of NPK. The soil was sampled from 0-60 cm depth after the wheat crop harvesting and was examined for soil NO 3 -1 nitrogen, available P and extractable K. Wheat straw and grain yields were taken at maturity showing significant improvement with increasing mulch application. Plant grain samples were also analyzed for nutrient (N, P and K) concentrations. The data were statistically analyzed using the ANOVA technique and the means of the treatments were compared using HSD (Tuckey’s) test with 5% significance. An eloquent increase in nutritional components NO 3 -1 , P and K of the top 30 cm soil layer and crop grain was observed. It was concluded that the application of organic wastes as soil cover not only conserves soil but also enhances its productivity. Therefore, it is recommended to use mulching materials to conserve soil and enhance productivity.


INTRODUCTION
The staple foodstuff of Pakistani nationals is Wheat (Triticum aestivum L.) fulfilling almost half the calories and protein requirements of a normal diet (Khalil and Jan, 2002). Rapidly increasing populations in developing countries like Pakistan have exploded food security problems. 11 million hectares of land is bound for wheat cultivation yielding yields 26 million tons of grains annually with a 3056 kg/ha average (GoP, 2021). It is consumed after harvesting because it is the cheapest feed source of all other alternate grain sources at present. According to a study that was conducted by Mustafa et al. (2004), the highest annual consumption per person is 125 kg. In addition to its usage in the agricultural sector to produce animal feed, wheat straw is also put to use in the industrial production of paper and power (Iqtidar et al., 2006). In Pakistan, many different cropping patterns are practiced, but around 60% of the land that is used for wheat cultivation is covered by rice-wheat and cotton-wheat patterns. Agriculture is the primary source of employment for around 60% of the workforce and contributes approximately 20% of GDP. At the farm gate, there are only 102 billion cubic meters of water available, which is sufficient to irrigate 82% of the cultivated land (14.64 M/ha) (GoP, 2022). Smallholding insists a farmer go for extensive cultivation to meet the food requirements of the family and the nation. In developing countries like Pakistan, it is becoming a major issue due to increased population the land holding is limiting resulting in more land degradation. Sustaining nutritional health of soil conservation agriculture is stated to be a solution with three main pillars i.e. (i) least disturbance using zero tillage or seed drilling, (ii) permanent covering of soil using organic or synthetic materials, and (iii) viable crop (exhaustive, restorative) rotations (Derpsch, 2005;Hobbs, 2007). Perturbed soils can be protected by mulch application that indirectly also water and nutrient content of soil (Barajas-Guzman et al., 2006). Established nutrient patterns with improved soil structure and organic matter on the application of mulch have also been established (Tiquia et al. 2002). Dry areas' agricultural systems have majorly focussed attention on mulch use (Adekalu et al., 2007). Mulching is highly fruitful in low rainfall areas and steep lands with high precipitation; however, variation in materials can be observed depending upon the objective of application i.e. improvement of soil physical condition or soil nutritional quality (Cook et al., 2006). Mulching alters the soil environment by regulating biochemical processes that lead to various nitrogen availability, N-use efficacy, and residual N accumulation in soil (Gao et al., 2009). N uptake is better synchronized with the slow release of N by decomposition of organic mulch residues that enhance N use efficacy and yields of the crop as leaching losses are prohibited than inorganic application (Stagnari and Pisante, 2010). Inorganic fertilizers in our environments are mostly broadcasted especially nitrogen on 2 nd and 3 rd splits that get exposed to air and irradiation resulting in more losses as compared to beneficial impacts (Malhi and Nyborg, 1990) while mulching may reduce volatilization losses on N (Bhagat and Verma, 1991) hereby increasing nitrogen use efficacy. Total uptake of N, p, and K by plant got enhanced by the application of mulch as compared to intensive tillage (Acharya and Sharma, 1994;Bhagat, 1990). Organic mulch application increases crop yields enhancing N uptake efficacy by up to 10 percent as compared to control treatments (Limon et al., 2000). Soil phosphorus is said to be unaffected by tillage because it is strongly dependent upon the clay mineralogy and soil pH (Lal, 2000) reported increased P content in the uppermost layers of soil by continuous application of organic residues as mulches. The same was the case observed for potassium with increased availability by application of straw mulches (Matowo et al., 1999). In light of the information presented above, the current investigation was devised to determine not only the amount of nutrients that wheat can absorb but also the amount of nutrients that can be preserved in the soil by the topsoil application of organic mulches.

MATERIALS AND METHODS
A field experiment using a Randomized complete block design (RCBD) was conducted during 2020-2021 at the research site of the Arid Zone Research Center (AZRC), D.I. Khan, to ascertain the impact that different mulches, applied at varying rates, had on the physicochemical properties of the soil and the quantity of wheat that was harvested. Random samples of the composite soil were taken from the experiment field before the planting of the crop. The soil samples were ground up, well mixed, and then sieved through a 2 mm screen before being assessed for their varied qualities after being air dried (Table 1).
The recommended amounts of NPK were administered at a rate of (120:90:60) kg/ha. Before planting and again at harvest, soil samples were taken using an auger to determine the nutrient content of the soil at depths ranging from 0 to 60 cm at intervals of 15 cm for each treatment. Using a spectrophotometer and chromotropic acid, the amount of nitrate-N in the soil was measured (Sims and Jackson, 1971). Spectrophotometric analysis was used to measure phosphorus (US Salinity Lab. Staff, 1954). The potash was measured using flame photometry using a potash filter (US Salinity Lab. Staff, 1954). The grain and straw yield (Mg/ha) was measured using standard agronomic procedures at the time of crop harvest and straw and grain samples were collected, digested (Moore and Chapman, 1986), and analyzed for N, P, and K contents using (US Salinity Lab. Staff, 1954) procedures. The experiment was conducted using RCBD. The significance of data was tested using the ANOVA technique and the treatment means were compared using (Tuckey's) HSD test (Steel and Torrie, 1980).

Grain yield (Mg/ha)
Grain yield is the main output of a crop because of Two mulches (Farm manure and Wheat straw) at levels i.e. CTRL = Control, WS 5 = WS mulch @ 5 Mg/ha, WS 10 = WS mulch @ 10 Mg/ha, FM 5 = FM mulch @ 5 Mg/ha FM 10 = FM mulch @ 10 Mg/ha which the whole headache is taken. As wheat grains are used as a staple diet, so, their increment is badly needed for every newer technique. It is discovered from ( Table 2) that mulching had a substantial boosting impact on the grain yield of wheat crops. Data regarding farm manure (FM) treatments shows that a notable upsurge of 0.86 and 0.49 Mg/ha in the grain yield of FM 10 and FM 5 than control was observed, respectively. This considerable increase in the grain yield is because of improvements in soil physical health due to the least outside commotion by (climatic factors i.e., rain and air or anthropogenic activity i.e., the applied irrigation), increasing soil nutrients by organic mulch mineralization along with uptake capacity because of water conservation in soil. Wheat straw mulch showed lesser but a considerable increase of 0.50 and 0.22 Mg/ha in WS 10 and WS 5 compared with the CTRL treatment.
Farm manure applications such as mulch improved the yield of grains more as compared to wheat straw because of nutrient enrichment and easy decomposition. The wheat straw having a high carbonto-nutrient ratio have a lower decomposition rate and lesser nutrient in the soil resulting in lesser yield. Huang et al. (2005) configured the same type of significant influence of straw mulch on wheat yield with 37%, 52% and 20, 26% increases in plant biomass and grain yields in 1997 and 1998, respectively. Bonfil et al. (1999) observed higher rooting depth and soil moisture contents in upper soil layers that improved grain yield. In addition, Glab and Kulig (2008) demonstrated that using mulched treatment resulted in greater grain production of around 6.79 tonnes/ha in comparison to the non-mulched treatment's 5.54 tonnes/ha. (Liu et al., 2002;Tolk et al., 1999) concluded that there was a net increase in the soil moisture contents, which made it easier for plant roots to access nutrients, which increased crop output. In the province of K.P.K. in Pakistan, where Shafi et al. (2007) conducted tests on the integration of residue and mulch, they found that grain yield increased by 23.7%.

Straw yield (Mg/ha)
Wheat straw is also an important part of the plant as it is used as livestock feed in fodder-scarce days of the year and it is also used as an organic amendment for agricultural field operations. But nowadays it has also become important as being used as a fuel for power generation in Pakistan. According to statistics shown in Table 2, mulching has a considerable impact on straw yield, increasing it by 0.75 and 0.44 Mg/ha in WS 10 and WS 5 from the control treatment. More farm manure application increases straw yield incidentally. For example, in FM 10 , straw yield increases by a mean of 0.78 Mg/ha, whereas in FM 5 , the increase is just 0.67 Mg/ha. Therefore, it can be concluded that treatments using farm manure result in much higher straw yields than controls, while these values are still lower than those of treatments using wheat straw. The performance of farm manure mulch is superior to that of wheat straw, as shown by the percentage increase in straw yield relative to control, even if wheat straw treatments result in higher overall straw yields. As more plant height was seen in farm manure mulches, they should produce more straw, but materials may have accumulated if wheat straw produced heavier straw than the farm manure, which might be the result of a flawed weight balance or a human error. According to Huang et al. (2005), the wheat crop experienced increases in grain yield and biomass on the order of (37 and 52%) and (20 and 26%), respectively, for two years. When comparing the control treatment with no mulch to the experiment with mulch, Bhatt et al. (2004) found that the trial with mulch produced a mean biological yield of maize crops that was 138% higher than the control treatment. According to Pervaiz et al. (2009), increasing the mulch level led to an 8.7% increase in crop biological yield, which was a substantial increase when compared to the level of control.

Grain nitrogen (g/kg)
The statistical behavior of the effects of the different mulching manures on the uptake of nitrogen by the wheat crop is shown in detail in (Table 2). Calculations revealed that the farm manure mulch treatment FM 10 produced grains with N content that were substantially more abundant (3.56 g/kg) than the WS 10 (3.41 g/kg). In the presence of farm manure mulch, the wheat crop greatly enhanced its uptake of nitrogen. Although its quantity is considerably lesser than farm manure but still wheat straw has radically enhance the nitrogen amount absorbed by the wheat crop. The results of Chaudhary et al. (1994), which demonstrate that increased soil health combined with well-aerated conditions can boost N uptake efficiency and increase crop yields, are consistent with our own. Limon et al. (2000) discovered that mulch application increased the crop's ability to efficiently absorb nitrogen by 10%. Bhagat (1990) carried out several research to determine the ideal proportion of conventional tillage and mulch for the greatest nitrogen absorption.

Grain phosphorus contents (mg/kg)
The distinct statistical behaviors of the wheat crop's ability to absorb phosphorus under the influence of the various mulch treatments are demonstrated in (Table  2). When compared to the wheat straw mulch treatment WS 10 , the amount of phosphorus found in wheat grain that was exposed to the farm manure mulch treatment FM 10 (0.19 g/kg) was found to be significantly greater (0.16 g/kg). The mulching lower the pH in the microenvironment around the plant root, releasing P that has been trapped in the soil and forming complexes with calcium compounds. All of these increases are thought to be the result of the release of P from the mulch's decomposed constituents.

Grain potassium contents (%)
Both mulching materials had a statistically significant impact on the potassium quantity in the wheat grains shown in (Table 2). Although there is no discernible difference between the two mulching materials when it comes to the evaluation of potassium concentration in wheat grains, both mulches outperformed the control treatment due to the large increase in K concentration. Regarding wheat straw mulch, the concentration of K in the grain increases significantly under WS 5 and WS 10 , by 15.08% and 28.26%, respectively. While the potassium content of grains under FM 5 and FM 10 increased by 17.3 and 31.4%, respectively, when farm manure mulch was used. The most logical explanation for the rise in potassium content is thought to be the soil's ability to hold onto moisture. Even though the soils of Pakistan are rich in potassium, the real issue is its release from the interlayer gaps of other soil minerals, such as mica.
When the soil contains more water, it flows to the interlayer gap where K's position causes it to be thrown into the soil solution and made available to the plant. Therefore, the same effect was considered here since mulch saved a significant amount of soil water that may have otherwise evaporated and released K from the interlayer gap, increasing its availability. Since K is not a plant structural component, little is thought to be released from the decomposition of mulching material, which is of no real significance.

Soil nitrate-nitrogen (mg/kg)
Mulch significantly affects soil NO 3 -1 nitrogen, according to the findings of statistical analysis of soil NO 3 -1 concentration (Fig. 1). Farm manure mulches FM 10 and FM 5 each increased soil nitrogen by 16.7 and 12.3% over control treatments, whilst WS 10 and WS 5 showed an increase in soil NO 3 -1 nitrogen concentration of 42.4 and 16.9% over control treatments. In light of the aforementioned findings, it is evident that wheat straw mulch increases soil NO 3 -1 levels more effectively than farm manure mulch. Except for WS 10 , the amount of nitrogen increases with depth under each treatment when the depth component is considered, while the significance of the results remains the same up to 30 cm. At a depth of 30 to 60 cm, there is no appreciable difference between the applied mulch treatments and the control in terms of NO 3 -1 nitrogen concentration. The increase in nitrogen content could be due to three different factors. One of them is the decomposition of organic mulches, which released nitrogen upon mineralization. Murungu et al. (2010) calculated that applying grazing vetch as mulch added around 111.5 kg N/ha to the field due to its fast decomposition and nitrogen release. Legume residues enhance the amount of N in the soil because they have a low C/N ratio and quickly break down to release N. The amount of inorganic nitrogen in the soil can be decreased by introducing additional carbon to the soil in the form of woody debris. However, until N availability is at its peak, this reduction only lasts for a few months to a year (Miller and Seastedt 2009;Perry et al. 2010). Mulch application enhanced soil moisture, according to Surya et al. (2000). This has important implications for crop water use, soil reactions that control the availability of nutrients in the soil, and better biological nitrogen fixation. Fig. 2 shows how mulching affects soil phosphorus (mg/kg) up to a depth of 30 cm. In the FM 10 and FM 5 treatment plots, the concentration of phosphorus rose by 141 and 34.14% in the 0-15 cm layer and by 119 and 31.9% in the 15-30 cm layer. The phosphorus content of soil does not increase at lower depths. In WS 10 plots 0-15 and 15-30 cm deep, wheat straw mulch increases phosphorus by 56.8 and 57.245%, respectively. WS 5 soil P content is 46.4% and 44.8% higher than the control under 0-30 cm. Results are not significant because there is no net increase in phosphorus concentration in the 30-60 cm deep range. P is released into the soil solution during mineralization because it is a structural component of applied organic matter. In Pakistan, calcareous soils that immobilize soil phosphorus due to high pH hinder growth. Olsen P fluctuated from year to year and was unaffected by altered tillage practices or variations in soil depth, according to Selles et al. (1999), but higher P concentrations were seen where mulch was applied. Mulch and P fertilizers increased soil P, according to Lal (2000).

Soil potassium (mg/kg)
Potassium in the soil is decidedly affected by mulching (Fig. 3). In FM 10 , WS 10 , and FM 5 , K concentrations of 12, 9.4, and 9% higher than CTRL were found, whereas other samples showed no appreciable difference. The concentration of K diminishes as we descend to the second depth. The following factors contribute to the greater K content of the top 30 cm of soil. In contrast to the upper layer, which has more extractable K because of its increased water content, Matowo et al. (1999) found that tillage treatments have no impact on this nutrient. Although Bhatnagar et al. (1983) observed no influence of residue incorporation on soil exchangeable K, Franzluebbers and Hons (1996) discovered more K in the top 5 cm of soil than in the subsoil.

CONCLUSION
The results of this study show that the application of organic mulches to the soil's surface during the transition phase ensures significant improvements in the soil nutrients' availability. The crop responded well to the better soil conditions, inducing fascinating physiological changes that ultimately led to higher yields. Following mulching, the plant's biomass and nutritional (N, P, and K) status both improved. Under the conditions of our experiment, 5 Mg/ha of wheat straw and farm manure added as mulching significantly increase yields, however, 10 Mg/ha of wheat straw and farm manure must be applied to ensure significantly positive effects on both the soil and several crop yield indicators. The findings presented lead one to the conclusion that the application of organic mulches to the soil's surface not only helps to cut down on the loss of soil nutrients but also helps plants take in more of those nutrients thanks to the mulch's slow and steady release of nutrients as they are mineralized.