The effects of deep tillage, straw mulching and farmyard manure on maize growth in loamy ... Deep tillage and straw mulch effects varied with soil type and.
P.R. Gajri
15
rt u l .
Soil Usr unll Manrrgrmmt (1994) 10, 15-20
Maize growth responses to deep tillage, straw mulching and farmyard manure in coarse textured soils of N.W. India P.R.Gajri, V.K. Arora & M.R. Chaudhary Abstract. The effects of deep tillage, straw mulching and farmyard manure on maize growth in loamy sand and sandy loam soils were studied in experiments lasting three years. Treatments included all combinations of conventional tillage (10 cm deep) and deep tillage (35-40 cm deep), two farmyard manure rates (0 and 15 t/ha) and two mulch rates (0 and 6 t/ha), replicated three times in a randomized block design. Deep tillage decreased soil strength and caused deeper and denser rooting. Mulching decreased maximum soil temperature and kept the surface layers wetter resulting in better root growth. Farmyard manure also improved root growth, and the crop then extracted soil water more efficiently. All three treatments increased grain yield in the loamy sand, but in the sandy loam only tillage and farmyard manure increased yields significantly. Deep tillage and straw mulch effects varied with soil type and amount of rainfall in the growing season. In the loamy sand the mean responses to deep tillage and mulching were largest in a dry year. A tillage-mulch interaction was significant in the loamy sand.
INTRODUCTION
C
OARSE textured alluvial soils developed under a hyperthermic regime in semi-arid subtropical regions of north west India contain very little organic matter and are structurally unstable. They are not only poor in available plant nutrients, but also retain little water and are very permeable. Super-optimal temperatures, rapid evaporation and increased transpirational demand during the cropping season dry the surface layers rapidly, causing an increase in mechanical impedance and restricted rooting. Because of these soil and climatic constraints and restricted rooting, crops grown on these soils suffer water and nutrient stresses leading to yield decreases. For efficient utilization of water and nutrients and improved crop yields, the zone of nutrient concentration must be moist and contain actively growing roots. This can be achieved by regulating the nutrient/water supply and/or accelerating root growth through modification of the soil physical environment. Subsoiling decreases bulk density and soil strength (Campbell et af., 1974; Bradford & Blanchar, 1977; Chaudhary et af., 1985) and increases root proliferation into the subsoil (Bennie & Botha, 1986; Arora et al., 1991; Gajri et a/., 1991). Organic mulches conserve moisture, decrease the soil temperature (Bansal et al., 1971; Khera et al., 1976) and improve root growth (Chaudhary & Prihar, 1974). Application of farmyard manure (FYM) improves nutrition and increases yields. However, there is little information on the combined effects of these practices on crop performance in India. This paper reports the effects of deep tillage, straw mulching and FYM on growth and yield
Department of Soils, Punjab Agricultural University, 1.udhiana-141004 India.
of maize on loamy sand and sandy loam soils in a semi-arid subtropical environment in N.W. India. METHODS AND MATERIALS Our field experiments from 1988 to 1990 were on deep alluvial loamy sand (Typic Ustipsamment) and sandy loam (Typic Ustochrept) soils at Punjab Agricultural University, 1,udhiana (30"50'N, 75^52'E, 247 m above sea level). The sandy loam retained 108 mm more water in a 1.8 m deep profile between field capacity and - 1.5 MPa matric potential than the loamy sand (Table 1). Both soils have little organic Table 1. Particle size distribution and water retention characteristics of the evperimental soils Particle size distribution (weight '%I) Soil depth (cm)
I m m y sand 0-30 30-60
Sand
Silt
xx x7
7 7
Clay
5
Water retention (volume, I%) Field capacity?
- 1.5 MPaI 7.3 8.0 7.8 6.3 6.3 6.2
10.1 10.1 8.7 x.7 8.7
xx
6
90-120 120-150 150- I XO Sand) loam 0-30 30-60 60-90 90- 120 120- 150
90 Yl
7 6
Yl
6
3 3
17.5 1x.5 17.2 143 14.7 14.7
1.50-1x0
74
1 -5 IX IX 20 20 17
I0 14 I4 I2 12 9
24.0 24.9 24.9 24.5 24.5 24.0
60-90
7.i 68 68 6X 6X
6 6 3
tlletermined I N SIIU 24 h after thorough wetting. 1Determined in a pressure plate extractor.
x.9
Maize growth responses in coarse textured soils of N.W. India
Ih
carbon ( < 0.4%). Mean monthly minimum and maximum air temperatures, United States Weather Bureau (USWR) class A open pan evaporation and solar radiation during the three cropping seasons are given in Table 2. T h e three years differed markedly in amount and distribution of rainfall (Fig. I ) . 'I'rcatments included all combinations of two tillage systems: ( I ) conventional tillage (CT) comprising one discing to 10 cm depth and two runs of a cultivator followed by packing and levelling with a wooden plank (2) deep tillage (DT) comprising 35-4Ocm deep subsoiling with a single tine chisel at 40 cm spacing followed by CT, t w o rates of farmyard manure: (3) 0 P"), (4) 15 t/ha (F), and two rates of mulch: (-5) 0 (M"), (6) 0 t/ha (M) paddy straw mulch spread between rows. Tahle 2. Mauinium and minimum temperatures, class A open pan e\anoration and \ o h radiation during the cronninv season Solar radiation (langleydday)
Air temperature (' C) Pan evaporation
\lonth
hlaximum
Minimum
(nim/day)
1988
1989
Junet July
37.3*1.2 33.3+1.3 32.0kO.l 33.1 kO.5
27.x*2.0 26.2+1.3 25.4k0.6 23.5k0.6
9.2k1.7 5.Xk1.2 5.1 k0.X 4.7+0.3
_ 316 458 402
_ 441 48X 476
AUguht
Septeniher
t\lid-end of June
1200
-
1100
-
loo0
-
800-
E 5700
-
400,1980
300-
The FYM consisted of cattle dung and remnants of straw and plant stacks fed to the cattle, and contained 1.0% N, 0.3%) P and 0.9% K on a dry mass basis. All trcatmcnt combinations were replicated three times in a randomized block design. Each plot measured 5.4 x 8 m. Sutticicnt buflir was kept on both sides of each plot to avoid wheeling and to maintain the same depth of tillage. Part of each buffer was used for irrigation channels and the rcmairrdcr was planted to maize. The fields were irrigated in the last week of May and subsoiled in the second week of June, by which time the subsoil had dried enough to permit maximum shattering. Immediately before sowing, FYM was spread uniformly over the appropriate plots, the whole of the field was irrigated and the seedbeds were prepared by conventional tillage. All plots were fertilized by drilling 25 kg P/ha as single superphosphate, 25 kg K/ha as potassium chloride and 5 kg Zn/ha as zinc sulphate. Maize (cv. Partap) was dibbled 22.5 cm apart in rows 60 cm apart between June 2 0 and 22 each year. Nitrogen (urea) was broadcast in three split applications of 50 kg N/ha each at seeding, 20 days after seeding (DAS) and 40 DAS. After a common irrigation of 75 mm at 15 DAS, irrigations of 7.5 mm werc applied after 50 mm evaporation from a USWR class A open pan. Unchopped paddy straw was spread o n appropriate plots immediately after sowing. Weeds were checked by preemergence herbicide and hand weeding. The crop was protected against insects and other pests. Areas of 10 mz were harvested in the last week of September to rccord dry matter and grain yield at 15% moisture. Soil penetration resistance was measured manually at tield capacity water content with a proving-ring cone penctrometer (30" cone angle and 1.33 cmz base area) ;it 30-40 random sites in all C T and D T plots (regardless of FY%I and mulch treatments) before seeding in 1988. Soil cores for determining root growth were taken a t 5 X ])AS in 19XX and 60 DAS in 1989 in the loamy sand. Soil samples were taken at 0.10 m depth increments down to maximurn rooting depth with a 0.05 m diameter auger from 4 sites on one side of a crop row by centering the auger 0, 10, 20 and 30 cm away from the base of the plants. The roots from each composite set of 4 cores were washed over a 1 mni screen and their length was measured by the line intercept technique (Newman, 1966). At harvest time in 1989, soil water content was determined gravimetrically in 0.3 m dcpth increments down to 1.5 m in the loamy sand. Soil temperature was measured with a mercury thermometer at 14.00 h at 5-8 day intervals during 1990 in the top 0.10 ni of D T M o F and D T M F plots. T h e statistical signiticance of treatment effects on dry matter and grain yield was inlirred from least significant difference (L.S.D.) tests, using analysis of variance for a three factor factorial randomized block design.
RESULTS AND D I S C U S S I O N
0
1
0
2
0
3
0
4 0 50 6 0 7 0 Days after ewdlng
I:ig 1. (:umulative rainfall distrihution in each year.
8 0 9 0
Soil strength Tillage decreased soil strength in the tilled layer (Fig. 2); the mean cone index (CI) in the 0-0.15 m layer was 0.63 MPa in DT plots and 0.99 MPa in C T plots in the loamy sand, and 0.58 MPa (DT) and 1.14 MPa (CI') in the sandy loam. In the 0.15-0.30 m layer it was 1.60 MPa ( I l l ' )
17
P.R. Ciajri rt ul. Cone index. MPa
0
1
2
3
r
I
I
I
E
d
P
3OL
I Sandy loam
Loamy sand -c conventional tillage
4deep Ullage standard deviation
I
Fig. 2. Soil strength profiles in top 30 cm of two tillage systems on the two soils at sowing. 1988.
and 2.52 MPa (CT) in the loamy sand, and 1.59 MPa (DT) and 2.75 MPa (CT) in the sand! loam.
Soil tetnperuturr In the loamy sand, straw mulch decreased the maximum soil temperature at 10 cm depth by 1.3-6.5 'C (Fig. 3). T h e decrease was larger during the early stages of crop growth and lessened with the development of crop canopy. Similar trends were observed in the sandy loam though the magnitude of temperature decrease was less (data not reported). Root growth
Table 3 gives treatment effects on rooting depth and root length index (RLI, cm root/cm* surface area in the rooted
-c
A
1
37
-
IE :
I-
343332 31
-
-
4 0
1
10
20
30
50 80 Days after seeding
40
70
Root length index 'Treatment
Whole profile
9.6k1.8 11.8+2.0
12.6+ 1.0 14.0k2.6 17.2 f 2.2 21.8 f 2 . 6 15.8k3.2 I8.4f 2.0 6.4 f I .4 13.2k3.2 10.8 f3.0 17.4k3.t 14.6f 3.0 18.4+2.6 1 l.8k 1.4 15.4+2.2
nomulch mulch standard deviation
38-
Y
Table3. Treatment effects on r w t length index (cm rwt/cmz surface area) in the rcxoting profile and depth of rooting of maize at silking on the loamv sand soil
80
90
Fig. 3. Maximum soil temperature at 10 cm depth in the loamy sand in 1990.
Helow 10 cm depth
3.0 f0.6 6.9 f 1.2 7.0 k 0.8 9.2f 1.4 8.9 & 1.2 13.7k 1.8 8.9f 1.5 11.4+ 1.4
1.8f0.4 7.3 1.6 s.n+ 1.2 11.5 f 1.8 8.3 f 2.0 12.7 f 2 . 3 7.2 k 1 .O 9.6+1.5
Rooting depth (cm)
60 60 60 60 60
80 60 80
60 100
80 100
I (m 120 100 120
profile) of maize at silking (60 DAS) in the loamy sand during 1988 and 1989. All three treatments affected these root growth factors. In 1988, when there were frequent rains during the first month of crop growth, tillage effects on depth of rooting were less pronounced than in 1989, when the crop was subjected to long drying cycles. In 1989, the root system in D T grew 40cm deeper than in C T without FYM and mulch, and 20 cm deeper than C T with FYM and mulch. T h e RLI was increased considerably by deep tillage in both years, but more so in 1989 than 1988. In 1988, RLI in the entire profile in DT was 23, 11, 27 and 16% greater
Maize growth responses in coarse textured soils of N.W. India
18
than C1' in F,M,, FM,, FoM and F M plots, respectively, whereas in I989 the increases were 100, 64, 26 and 39'10, respectively. Tillage effects on RLI were greater below 10cni depth than those in the surface IOcm. T h e RLIs below 10 cm with D T were 130, 31, 54 and 28%)greater in F,M,, FM,, F,M and F M than with CT in 1988 and 306, 153, 66 and 36% greater in 1989. These data suggest that 111' effects on RIA were less in the presence of FYM and mulch. In the absence of FYM, mulching (averaged over tillage treatments) increased total RLI by 9.4 and 6.7 cm/cm2 in 1988 and 1989, respectively. Ikcause of their small water retention capacity, these soils dry quickly with a sharp increase in soil strength. Gajri rt (11. (1991) observed that each weight percent decrease in moisture increases their CI by 0.21 MPa. Denser rooting in D T compared to C T is attributable to decreased soil strength (Fig. 2), as root growth is often inversely related to cone indev (Taylor rt ( i l . , 1966). Mulching decreased the soil temperature and kept the surface layers wetter. In 1988, the water content of the surface 10cm layer of the mulched plots at 45 DAS was 1.4% greater than that of the unmulched plots. Thus mulching decreased soil strength through its effect on soil water, and thereby alleviated constraints to root growth and proliferation. lliitrr use A s a consequence of better rooting, the crop in the D T plots utilized the profile water more efficiently, as is evident from 1989 harvest time water profiles of the loamy sand soil
(1;ig. 4). The crop in D T extracted 29 mm more soil water than that in CT in the unmulched and 17 mm more in the mulched plots. ).rr1r/ Grain yields were significantly affected by year and treatments, particularly in the loamy sand (Table 4), where yields Soil water, weight percent 0
30
6
7
8
9
10
1
I
I
1
-
60-
E
f
-
I
90-
120
-
'T Fig. 4. 'l'illage and mulch effects on 1989 harvest-time soil water profiles in the loamy sand.
Table 4. Effect of tillage, Farmyard manure (I:),and SITJ~V niulch ( \ I ) main yield (t/ha) of maize (in loamv sand and sand\ Iuun wil\
I .oam! sand
Sandy loam I:,,
1:
1:,1
oii
1.'
Year
Tillage
h4,
hl
hi,,
bl
%I,,
11
\I,
\I
I988
(3' lYl*
1.4 2.x 0.5 3.4 1.0 2.1
2.7 2.9 3.9 4.8 2.0 2.x
2.3 3.6 1.3 4.9
3.5 3.4 4.2 2.7 3.3
4.0 4.0 4.j 5.1 3.7 3.8
4.0 4.x 4.9 4.9 3.4 4.2
4.5 4.x
1.9
5.0 4.6 3.x 4.7 2.7 3.0
1989
c:r
1Y1' 1990
C'r IN'
2.x
5.5
4.0
S.2 4.3 4.2
Means
Year
I9XX
2.9
1Y X') 3.6
I090
IYXX
2.4
4.7
(:I. 1x1. 2.3 3.5 Mulch h'" hl 2.3 3.i I'Y rvl I:, 1: 2.5 3.3 Ixast significant differences (P=O.O5) Years 0.34 Tillage 0.27 Mulch 0.27 IYM 0.27 Year x tillage 0.46 Year x mulch 0.46 'lillage x mulch 0.3X 'IUage
1YX') 4.x
(:I' 4.2
~4, 4.3
IYIJO 3.X
I SI' 4 .5 \I 4. 5. 1: 4i
4.2 0.4') 0.2 I N.S. 0.2 I N.S. 0.37 l.S.
were generally less than in the sandy loam. Grain yields were also less in 1988 and 1990, when there were more frequent and heavier rains and solar radiation w a s less than in 1989 (Fig. 1 and Table 2). Farmyard manure increased the mean yield h y 0 . X t / h a in the loamy sand and by 0.3 t/ha in the sandy loam. Tillage and mulch affected the yield significantly, but the magnitude of response varied with soil type and year. Yield was 52";1 greater with DT than with C T in the loamy sand and 7",1 greater in the sandy loam. T h e maximum response to IYI' was observed in the dry year of 1989 in the loamy sand. Deep tillage increased grain yield over CT by 2X?/o in 198X, 88% in 1989 and 47% in 1990 in the loamy sand, whereas in the sandy loam yield increases with D'T weIc nil, 1 1 ' + ~ and 14% in the same three years. These observations support earlier findings (Unger, 1979; Arora rt ul., 1991; Gajri et d., 1991) that the benefits of deep tillage are greater on less retentive, coarse textured soils and under low rainfall. As with deep tillage, yield response to mulch was greater in the loamy sand in the drier year. In the sandy loam, mulch even decreased the yield slightly in 1988. From the analysis of 10 years' data on maize response to mulching under similar soil and climatic conditions, Prihar & Arora (1980) reported that mulching increases grain yield signiticantly (4-36%) in loamy sand in all years, but in sandy loam the response ranged from - 1 1 to 18%, depending upon the amount and pattern of rainfall. Deep tillage and mulching individually increased grain yield to almost equal extents in the loamy sand. A plot of grain and dry matter yield in different treatments (averaged over FYM) during the three years (Fig. 5) shows that harvest index (HI, the ratio of grain yield to abo\c-
P.K.Gajri ci ril. loamy sand
6r
sandy loam
CTM, 0 DTM,
8
..
A
A
CTM 0
5
19
DTM 0
4t
A"
3.
2l
2
3 3 3
A'
0
1
0 3
1
0 2
2
4
6
0
10
12
14
16
17
Dry matter, Vha
Fig. 5 . Influence of deep tillage and straw mulching on grain and dry matter yield of maize on the two soils. Numerals 1, 2 and 3 indicate 1988, 1989 and 1990 crop seasons, respectively.
ground dry matter) was least in CTM, in the loamy sand, indicating that the crop in this treatment suffered from water stress during grain-fill. Deep tillage and mulching helped the crop to overcome this stress and conserved HI. In the loamy sand, HI averaged 0.36 with DT and 0.35 with mulch but only 0.31 with CTM,. However, in the sandy loam, HI was 0.36 irrespective of tillage or mulch. Deep tillage and mulch affected yield through their influence on depth and density of rooting (Table 3). Even irrigated crops with restricted root systems are reported to be more susceptible to water stress than those with deeper, well developed root systems (Unger et d.,1981). Deeper and denser rooting in deep tilled or mulched soil helps plants to use water and nutrients from the subsoil more efficiently (Arora rt id., 1991). The three years' mean yield of 1.0 t/ha in CTF,Mo in the loamy sand soil was increased to 1.8 t/ha with FYM application, and to 2.8 t/ha with deep tillage or straw mulching (Table 4). T h e combination of FYM and deep tillage increased yield to 3.8 t/ha; FYM and mulching increased it to 3.5 t/ha. Farmyard manure supplemented nutrient supplies. Deep tillage improved the soil physical environment primarily by decreasing soil strength. Straw mulching decreased soil temperature and increased the moisture content of surface layers, thereby improving the root environment. The nutritional effects of paddy straw were assumed to be negligible as it has a wide C : N ratio (70-80: 1) and it was spread between plant rows as a mulch and not mixed into the soil. It seems that maize yield on the less retentive loamy sand soil is constrained more by the adverse soil physical environment than by nutrient supply. The alleviation of physical constraints by decp tillage and mulching significantly improved crop yield, though the improvement was less on the more retentive sandy loam than on the loamy sand.
CONCLUSIONS A proper combination of management practices like deep tillage, mulching and manuring, which increase depth and density of rooting, can enhance the crop productivity of less retentive coarse textured soils in arid and semi-arid environments by alleviating water and nutrient stresses.
REFERENCES v,k., G A J R I , P.K. & PRIHAR, S.S. 1991. 'I'ikIge effects on corn in sandy soils in relation to water retentivity, nutrient and water management, and seasonal evaporativity. Soil ritirl T'illqe Resrurrh 21, 1-21. I ~ A N S A I . . S.P.,G A J R I , P.K. & PRllIAR, S.S. 1971. Effect Of mulcheson water conservation, soil temperature and growth of maize and pearl-millet. InJiuti J~iiiniul~J.4gnculrwul .S&til.es 41, 467-473. H E ~ K I EA.T.P. , & ROTIIA, F.J.P. 1986. Effect of deep tillage and controlled traffic on root growth, water use efficiency and yield of irrigated maize and wheat. Soil und 7illugr Reseurdi 7 , 85-95, R n m F o R i ) , J.M. & hAK
