Effect of spot tillage on maize crop growth parameters

Introduction

Maize (Zea mays) is one of the most crucial cereal crops globally, serving as a staple food for millions of people. The Maize is the third most significant food crop after rice under Indian scenario (Murdia et al., 2016) [1] . Due to one of the most resilient developing crops, maize (Zea mays L.) has a larger range of adaptation under a variety of agro climatic situations. Due to its highest genetic production potential among all cereals, maize is referred to as the "queen of cereals" worldwide. It accounts for 39% of the world's grain production and is grown over approximately 190 million hectares across 165 nations with a greater diversity of soil, climate, biodiversity, and management techniques (APEDA, 2020). Excessive soil compaction is considered as the prime reason for the physical degradation of agricultural soils (Nawaz et al., 2013) [2] . The soil compaction was induced wheel load of agricultural machinery, tire dimensions, tire-soil contact characteristics and number of wheel passes (Obour and Ugarte 2021 and Gao et al., 2007) [3,4] . Severe soil compaction hindered substantial nutrition and moisture absorption, reducing root development and distribution (Bengough et al., 2011 and Schjønning et al., 2016) [5,6] . The yield penalties caused by compaction in maize fields have been documented to reach 43% (Voorhees, 2000) [7] . The way that various crops react to compacted soil varies greatly. The emergence of maize, barley, and soybean seedlings is more impacted by soil compaction. According to a recent study, the compaction of agricultural tractor tyre systems decreased corn height in the first two years, while for soybeans, this effect became considerable in the third year (Shaheb, 2020) [16] . According to studies, soil compaction increases the soil's mechanical strength and decreases its porosity, which has the greatest effects on the root penetration capability (Kirby & Bengough 2002; Kristoffersen and Riley 2005) [17,18] . Tillage is the mechanical manipulation of soil to create a favorable environment for seed germination. Tillage is one of the most important methods to reduce the soil compaction (Daniells, 2012) [9] . Soil physical properties were greatly influenced by tillage practices (Mosaddeghi et al., 2009) [11] .

Crop yield, root distribution, plant population density, and seedling emergence were all impacted by changes in the physical properties of the soil (Khurshid et al., 2006) [15] . Different tillage practices create different soil conditions which may affect the growth and yield of maize. Deep tillage and continuous tillage over a period of time leads to soil erosion, soil degradation, soil structure gets diminished, reducing soil productivity and soil organic carbon and also it consumes lot of fossil fuels adding up to greenhouse gas emissions. Although zero or no tillage had given good results in conserving soil moisture and other resources in field but long-term effects may leads to increase in bulk density, which is not conducive to maize growth ultimately ending up in reduced yields. To address the problems of deep tillage and zero tillage, a minimum tillage concept called spot tillage was introduced in the present study. Spot tillage is one type of tillage practice where a specific and minimum area, which influences the effective root zone of maize plant, is disturbed to a particular depth and width for seed placement. This tillage practice ensures resource conservation, avoids soil erosion and also reduces draining of nutrients from soil. There were only few studies are available about spot tillage, so a study is needed on spot tillage. The present study is aimed to understand the effect of spot tillage on maize growth parameters.

Material and methods

Site description

The study was conducted at the experimental field of the Division of Agricultural Engineering, ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi. The maize variety Pusa HQPM-1 was selected for the study. The experimental field had sandy loam soil and covered a total area of 108 m², with dimensions of 6 m × 18 m (width × length). Maize was sown at a spacing of 60 cm between rows and 20 cm between plants. A Randomized Complete Block Design (RCBD) was adopted to evaluate manual sowing under different tillage combinations, and the experimental design and statistical analysis were performed using SAS software. The experimental layout for manual sowing of maize under the selected tillage combinations is presented in Table 1. These treatments combinations included variations in seed placing zones, seed placement depth, and consecutive tillage activities for manual sowing, as detailed in Table 2. The three levels of diameter selected were 5, 10 and 15 cm, depth selected were 5, 10 and 15 cm and tillage types selected were one time tilling, two time tilling and three-time tilling. Diameters of 5, 10 and 15 cm, depth of 5, 10 and 15 cm and tillage types of one-time tilling, two time tilling and three-time tilling were involved in the experiment respectively. A series of operations carried out were mentioned in the figures a, b and c. Agronomical practices like nutrient application, irrigation, weed removal were precisely carried out to ensure proper growth of maize plants. The critical soil parameters for the measurement of tilth index of the spot tillage zone in manual sowing methodology were bulk density (BD), cone index (CI), aggregate uniformity coefficient (AUC), soil organic matter (SOM), and plasticity index (PI).

Sample collection Bulk density

The bulk density was measured by core sampler method as delineated by Arshad et al. (1997) [19] . The specific volume of core was inserted into the soil, removed slowly without the loss of any soil contents and then it was weighed. This soil sample subsequently dried in oven for 105 o C and its weight was measured. It was calculated by equation 1:

BD(g/ cm 3 )= (Weight of oven-dry soil in grams) (Volume of soil in core sampler in cm 3 )

Cone Index (CI)

The cone index was measured by cone penetrometer. The process involved placing the cone (3 mm base diameter and an apex angle of 60 degrees) on the soil surface with the shaft held vertically, and the cone's base securely positioned on the soil (Perumpral, 1987) [21] . The determination of soil cone index utilized the expression (Equation 2) recommended by Macmillan (2002), assessing the resistance encountered by the cone during penetration.

CI, kPa= Force on the cone Base area of the cone

Aggregate uniformity coefficient (AUC)

Sieve analysis is fundamental technique used for determining aggregate uniformity coefficient (AUC). It involves standard set of sieves (No. 4 sieve (4.75 mm) to the No. 200 sieve (0.075 mm) were shaked thoroughly with progressively smaller square openings. For interpretation convenience, parameters like D 10 , D 30 , and D 60 , corresponding to grain diameter (in mm) at 10%, 30%, and 60%, respectively, were utilized. Additionally, the coefficient of uniformity (Cu), acting as a shape parameter, was computed according to the method outlined by Kaliakin (2017) [20] using Equation 3.

Plasticity Index (PI)

For the present study Liquid limit and Plastic Limit were calculated to obtain the Plasticity index (PI). The plastic limit (PL) was determined by rolling out a thread of the fine soil portion on a flat, non-porous surface, following ASTM Standard D 4318. The liquid limit was find out by Casagrande's apparatus. The test follows ASTM standard, allowing interpolation for the moisture content requiring 25 blows or using a correction factor for liquid limit determination from a single moisture content test. Plasticity index was calculated by Equation 5 (Kaliakin, 2017) [20] .

The soil descriptions basedon PI categorize the non-plastic soils with a PI of 0, slightly plastic soils with PI less than 7, medium plastic soils with PI between 7-17, and highly plastic soils with a PI exceeding 17. The soils with a high PI predominantly consist of clay, while those with a lower PI tend to be silt-dominated. Soils with a PI nearing zero typically lack significant clay or silt content, indicating minimal fines.

Soil organic matter

In our present study, soil organic carbon (OC) was determined using the Walkley-Black (WB) method established by Walkley and Black in 1934. This method involved oxidizing carbon with acidic dichromate (Cr 2 O 7 2-) followed by titration with ferrous sulphate to determine the amount of unreacted dichromate (Plate 3.11). The OC was then calculated from the difference between the total dichromate added and the unreacted amount. This methodology provides an estimate of soil organic matter (OM) based on OC determination. The calculation of OC, followed the Equation 6.

OC, % = (mL b -mL s ) 0.195

Where, mL B is the Blank value and mL S is for soil sample

Tilth index (TI) Calculations

In this study, a scientific approach was employed to develop a "tilth index" by integrating five key soil physical properties: bulk density, cone index, aggregate uniformity coefficient, organic matter content, and plasticity index. The resulting index, ranging from zero (indicating conditions unusable for plants) to one (representing a nonlimiting environment for plant growth), offers a comprehensive assessment of soil tilth. (Karlen et al., 1990). Hence, the tilth index is a vital indicator of soil quality and structure and it was calculated systematically using the all gathered soil parameters mentioned above. The derived tilth index values provided valuable insights into soil tilth and health as provided in the Equation 7.

Where, CFx is the tilth coefficient for the soil property (X), and A 0 , A 1 , A 2 are constants. The tilth index (TI), was estimated as the multiplicative combination of the tilth coefficients (Equation 8), and tilth coefficients were normalized to range between 0 and 1. This normalization technique was considered based on the productivity index developed by Neill (1979). Table 3 provides the insights into the limiting, non-limiting and critical values of tilth coefficient.

Where, TI is the tilth index, CF x is tilth coefficient for soil property (X). The critical crop parameter which helps in determining optimum tilth index were plant height, leaf area index, root length and cumulative root volume. In the present study, crop parameters were systematically assessed at three distinct intervals-30, 60, and 90 days after sowing.

Plant height

The measurement of PH, a crucial indicator of growth, was conducted using a precise measuring tape or metric rulers to accurately determine the vertical distance from the plant base to the apex of the tallest shoot.

Leaf area index

The leaf area was precisely quantified using a LI-3100C area meter. This equipment accurately measured the leaf area in square centimeters (cm²).

Root parameters

The root samples were systematically collected from crop rows at 30, 60, and 90-day intervals during their growth period using a root auger. Root parameters such as root length and root volume were measured. This involved scanning the washed roots using a LA2400 scanner (Plate 3.14a), a tool recommended by the Division of Plant Physiology, ICAR-IARI, New Delhi, and employing winRIZHO software (Plate 3.14b) for analysis. This scientifically sound methodology ensured accurate assessment and quantification of root characteristics in our research, aligning with established practices in the field. All these above findings were analysed later by the application of statistical tools in the context of tilth index calculation and plant growth analysis under the experimental conditions.

Results and Discussion

Effects of soil parameters on the tilth index in manual tilling and sowing experiment.

The statistical analysis of manual tilling and sowing experiments reveals substantial variations in soil properties among different treatments. The calculated coefficients and tilth index values indiactes significant differences, providing valuable insights for informed agricultural soil management decisions. Continuing the analysis, the calculated bulk density ranged from 1.36 to 1. 4. Importantly, the tilth index, a key parameter reflecting overall soil quality, demonstrated variations among treatments. Specifically, Treatment T 1 consistently displayed the lowest tilth index of 0.32, while T 3 consistently showed the highest tilth index of 0.57. During the 30, 60, and 90-day plant growth period, a thorough investigation was conducted to assess the individual and interaction effects of key parameters, namely planting depth and tilled zone diameter. The results indicated significant differences in these effects, highlighting the distinct impact of each factor on plant growth. The high R-square value of 0.965, 0.963994, and 0.963420 at 30, 60, and 90 days respectively underscores the reliability of the model in explaining the variation in plant height based on the specified parameters.

Effect on manual tilling and sowing on the plant height

Conclusion

This study was conducted thethe effects of spot tillage on maize crop growth parameters. Based on the results obtained, manual tilling and sowing yielded that the soil parameters, bulk density ranged from 1.36 to 1.68 g/cm³, cone index range of 1.37 to 2.97 MPa, aggregate uniformity coefficient varied from 1.90 to 4.52, soil organic matter content ranged from 0.027% to 0.048%, and plasticity index values ranged from 0.21 to 0.38. Manual tilling and sowing the treatment T 1 consistently displayed the lowest tilth index of 0.32, while T 3 consistently showed the highest tilth index of 0.57. Across the 10*15*T 3 and 15*15*T 3 treatment combinations, all crop parameters demonstrated higher values, indicating the overall effectiveness of thespot tilling instead of tilling the whole field for normal growth of maize crop.Thus, spot tillage is an effective and efficient alternated method of sitespecific tillage in which highest tilth index is obtained along with normal growth of maize crop.

Acknowledgement

AcknowledgementThe authors sincerely acknowledges the Division of Agricultural Engineering, ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi, for providing the necessary facilities and support to carry out this research work.

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