Corn growth and yield responses to starter fertilizers in conservation-tillage systems

Soil & Tillage Research, 7 (1986) 135--144 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

CORN GROWTH AND YIELD RESPONSES IN CONSERVATION-TILLAGE SYSTEMS

TO STARTER

135

FERTILIZERS

J.T. TOUCHTON and F. KARIM

Agronomy and Soils Department, Alabama Agricultural Experiment Station, Auburn University, AL 36849 (U.S.A.) (Accepted for publication 16 August 1985)

ABSTRACT Touchton, J.T. and Karim, F., 1986. Corn growth and yield responses to starter fertilizers in conservation-tillage systems. Soil Tillage Res., 7 : 135--144. The purpose of this 3-year field study, which was conducted on a Norfolk sandy loam (Typic Paleudult), was to determine if initial growth and final yield of corn (Zea mays L.) grown in conservation-tillage systems (chisel plow and strip tillage) could be improved by the application o f starter fertilizer. Treatments consisted o f six starter fertilizer combinations (0--0--0, 24--0--0, 0--26--0, 0--0--66, 24--26--0, 24--26--66 kg ha-' of N--P--K, respectively). The initial soil pH was 6.0 and soil test P and K levels were high. Side-dress N (224 kg ha-') was applied 6 weeks after planting. The corn was planted with an in-row subsoiler planting unit and the fertilizers were placed in the subsoil tracks. Plant heights 6 weeks after planting were greater with than without starters, but this difference was primarily due to N. Concentrations of N, P and K in the young plant tissue, regardless of tillage, were increased when these nutrients were included in the starter combinations. Nitrogen concentrations in the ear leaf were not affected by treatments. Leaf K was higher with than without K-containing starters each year, but leaf P was higher with than without P-containing starters in only 1 year. Grain yields were increased b y the N-containing starter fertilizers each year. The yield increases were more closely related to differences in early-season plant growth than to differences in nutrient concentrations in plant and leaf tissue. In 2 years, the N--P--K combination resulted in highest yields, but in the other year, N--P was adequate. Higher grain yields were obtained with the striptillage than chisel-plow system in 2 of the 3 years.

INTRODUCTION Although many advantages have been reported for conservation tillage, t h e s h i f t f r o m c o n v e n t i o n a l t o c o n s e r v a t i o n - t i l l a g e c o r n p r o d u c t i o n is s l o w in m a n y a r e a s . T h i s s l o w s h i f t m a y b e d u e t o p o o r e r c o r n g r o w t h in c o n s e r v a tion than conventional-tillage systems during the early part of the growing season and to lower yields sometimes obtained with conservation tillage. T h e s e d i s a d v a n t a g e s a r e s e l d o m r e p o r t e d in t h e l i t e r a t u r e a n d m a y b e s o m e what limited to the Southern Coastal Plains of the U.S.A. (Austin, 1972).

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136 The poor early-season growth in conservation-tillage systems may be associated with early planting in cold soils (Unger, 1978; Warrington and Kanemasu, 1983). In the Lower Coastal Plains, optimum corn planting dates range from late February to mid-March (Ball, 1981). During this period, the soil temperature fluctuates widely and is often low for several consecutive days. Conservation tillage, especially when large amounts of mulch are left on the soil surface, results in lower soil temperatures than conventional tillage (Blevins and Cook, 1970; Phillips, 1974), which can compound problems associated with low soil temperatures. Slower than normal growth with low soil temperatures is probably due to a combination of poor root growth (Knoll et al., 1964; Beauchamp and Lathwell, 1967) and low nutrient availability (Ketcheson, 1968; Reyes et al., 1977). Poor seedling growth, resulting from low nutrient availability in cold soils, can occur irrespective of residual soil fertility levels (Touchton and Hargrove, 1983). Placing small amounts of soluble fertilizers in close proximity to the seed at planting, commonly referred to as starter fertilizer applications, will help alleviate the detrimental effects of cool weather on early plant growth. In both greenhouse and field studies, Bates et al. (1966) reported increased nutrient uptake, faster growth, earlier maturity and higher corn (Zea mays L.) yields with the use of seed-placed fertilizers. Similar results from field studies with grain sorghum (Sorghum bicolor L. Moench) were reported by Touchton and Hargrove (1983). Ketcheson (1968) reported that the beneficial effects of starter fertilizers on corn yield were greatest when temperature conditions favored low corn yields (low soil temperature--high air temperature). Nutrients used in starter fertilizer studies have consisted of various N-P--K combinations, but a strict definable starter fertilizer combination does not exist. Both N and P are considered to be primary ingredients in starter fertilizers because of the slow mineralization of organic to inorganic N (Cassman and Munns, 1980; Blevins et al., 1983; Dick, 1983), and slow release of solid- to solution-phase-P (Arambarri and Talibudeen, 1959a,b; Wallingford, 1978) in cold soils. Slower plant growth in untilled than tilled soils may also be due to poorer aeration or the lack of tillage-induced aeration in untilled soils. Poor aeration results in both poor root growth (Bertrand and Kohnke, 1957; Luxmoore and Stolzy, 1972; Bauder et al., 1981) and slow mineralization rates (Doran, 1980; Bauer and Black, 1981; Blevins et al., 1983; Dick, 1983). A combination of lower soil temperatures and poorer aeration in untilled than tilled soils may well enhance the need for starter fertilizers in conservation-tillage systems. The objectives of this study were to determine if starter fertilizers would improve the growth and yield of corn grown in a conservation-tillage system and to determine if corn responses to various starter combinations would vary among tillage systems.

137 MATERIALS AND METHODS This field study was conducted for 3 years in the Southern Coastal Plains o f the U.S.A. (Austin, 1972) (latitude 32 ° 26' N and longitude 85 ° 54' E) on a Norfolk sandy loam (Typic Paleudult). The soil was cropped in soybeans {Glycine max (L.) Merr.] in 1980 and after corn harvest in 1981 and 1982, the experimental area was seeded in cowpeas [Vigna unguiculata (L.) Walp.]. The initial soil pH, cation exchange capacity and organic matter content were 6.0, 4 meq per 100 g and 1.0%, respectively. Double acid extractable P, K, Ca and Mg levels were 1 5 0 , 1 1 0 , 9 0 0 and 100 kg ha -1, respectively. Soil test levels for P and K were high (Cope et al., 1981). Dolomitic limestone (2.2 t ha -1) was applied to the experimental area after harvesting corn in 1981. Treatment variables consisted of 2 tillage systems and 6 starter fertilizers. Tillage treatments were chisel plow (CP) and strip tillage (ST). In the chiselplow system, the soil was disked, chiseled, disked and rotary tilled 1 day prior to planting. The distance between the chisel blades was 15 cm and the depth o f chiseling was 20 cm. In the strip-tillage system, corn was planted in the previous crop stubble, which was soybeans in 1981 and cowpeas in 1982 and 1983. In both tillage treatments, the corn was planted with an in-row subsoil planting unit. The use of the in-row subsoiler resulted in a tilled strip 15--20-cm wide at the soil surface and tapering to 5 ~ m wide at the 20-cm soil depth. The starter fertilizer treatments were: (1) 0--0--0, (2) 24--0--0, (3) 0--26--0, (4) 0--0--66, (5) 24--26--0 and (6) 24--26--66 kg ha-' of N--P--K, respectively. Ammonium nitrate (34--0--0), concentrated superphosphate (CSP, 0--46--0) and muriate of potash (KCI, 0--0--62) were used for the N, P and K starters. Diammoniumphosphate (DAP, 18--46--0) was used for the N--P combination and DAP plus KCI was used for the N--P--K combination. The fertilizers were mixed with 10-mesh-size crushed dolomitic lime so that a constant volume of material would be applied to each plot. The application rate was 336 kg ha-' of material. The 0--0--0 treatment consisted of 336 kg ha-' of crushed dolomite. The fertilizers were applied in the in-row subsoil track at planting and the effective mixing zone was approximately 50 mm wide and 150 mm deep. Fertilizer concentrations within the mixing zone were approximately 15 times higher than the field equivalent rates. The experimental design was a split plot within a randomized complete block replicated 4 times. Tillage systems were in whole plots and starter fertilizers were in sub-plots. Plot size consisted of 6 rows (76-cm row width) of 10 m length. Corn (Zea mays L. cv. "Pioneer 3369A") was planted on 20 March 1981, 16 March 1982 and 2 May 1983. Seedingrate was 80 000 seeds ha-I and the population was thinned to 60 000 plants ha-' after stand establishment. Weeds were effectively controlled each year with a tank mix of paraquat (I,

138

l
Soil pH values in the subsoil tracks (mixing zone o f starter fertilizers) of the no starter checks were 5.5 and 6.2 in 1981 and 1982, respectively. This difference was due to autumn application of lime (2.2 t ha -I) in 1981. In 1981, N in the starter reduced soil pH levels by 0.4 units, but these reductions were not found in 1982. Soil P and K levels reflected starter fertilizer applications. Average soil-test P levels for treatments with and without P were 98 and 71 pg g-l, respectively and both were in the "very high" soil test TABLE I Plant h e i g h t ( c m ) 6 w e e k s a f t e r p l a n t i n g as a f f e c t e d b y s t a r t e r fertilizer a n d tillage systems a S t a r t e r fertilizer

Year

N--P--K

1981

1982

1983 b

(kg ha-' )

0--0--0 24--0--0 0--26--0 0--0--66 24--26-0 24--26--66 FLSD (0.10)

CP

ST

47 65 52 53 68 71

43 48 48 47 58 46

36 37 37 37 50 49

30 44 29 25 48 48

7

5

5

5

a All values are averaged over tillage systems, except where interactions existed between tillage a n d s t a r t e r fertilizers. b C p = chisel-plow tillage; ST = strip tillage.

139

rating (Cope et al., 1981). Soil-test K levels for treatments with and without K averaged 105 and 40 ~g g-', respectively, in 1981 and 70 and 35 ug g-' in 1982. Concentrations of 40 ~g g-1 and higher are required for a "high" soil test rating. Early season plant height (6 weeks after emergence) was affected by starter fertilizer treatments each year {Table I). Interactions between tillage systems and starter fertilizers occurred only in 1983. In 1981, differences in plant heights among starter fertilizers were due primarily to N. Average plant height was 51 cm when N was n o t included in the starter fertilizer and 68 cm when it was included. In 1982, the primary plant height response was to the N--P combination, but there was no response when K was included with the N--P starter. In 1983, plant heights were greater with the chisel-plow than strip-tillage system, except when N-containing starters were applied. In the chisel-plow system, only the N--P-containing starters improved heights, but N alone was adequate with strip tillage. In 1981, concentrations of N, P and K in the y o u n g plant tissue were not affected by tillage systems or by tillage × starter fertilizer interactions, but the nutrient concentrations were directly related to nutrients applied in specific starter combinations (Table II). When N, P, or K were included in a starter fertilizer combination, concentrations of these nutrients averaged 3.03, 0.63 and 4.22% (w/w), respectively and when they were omitted from the combinations, average concentrations were 2.25, 0.43 and 3.33% (w/w), respectively. According to Plank's (1979) tissue elemental sufficiency range recommendations for y o u n g corn plants, N (which should range between 2.5 and 4.0%, w/w) was the only deficient element. T A B L E II Nitrogen, P and K c o n c e n t r a t i o n s (%, w / w ) in plant tissue 6 weeks after emergence in 1981 and 1982 as affected by starter fertilizer and tillage system a Starter fertilizer N--P--K ( k g h a -1)

Nitrogen 1981

1982

Phosphorus

Potassium

1981

1981

1982

1982 b CP

ST

0--0--0 24--0--0 0--26--0 0--0--66 24--26--0 24--26--66

2.24 3.01 2.40 2.11 3.20 2.87

2.23 2.32 2.19 2.14 2.36 2.21

0.43 0.43 0.58 0.44 0.70 0.62

0.33 0.30 0.35 0.31 0.39 0.35

3.08 3.41 3.67 4.51 3.16 5.28

3.52 2.56 3.26 3.72 2.76 4.44

2.90 3.14 3.18 3.58 3.08 2.80

F L S D (0.10)

0.29

NS

0.53

NS

0.53

1.08

1.08

aAll values are averaged over tillage systems, e x c e p t w h e r e interactions existed between tillage and starter fertilizers. b CP c h i s e l - p l o w tillage; ST = strip-tillage. =

140

In 1982, N concentrations in the whole plant tissue did n o t vary among tillage systems or starter fertilizers. Phosphorus levels followed trends similar to those found in 1981. There was an interacting effect of tillage and starter on K concentrations, but this interaction was due entirely to a higher K level with the N--P--K fertilizer in the chisel-plow system than with any other starter fertilizer in the chisel-plow or strip-tillage system (Table II). Nitrogen concentration in the ear leaves at early silking averaged 2.80% (w/w) and was not affected by starter fertilizers or tillage systems in either year. In 1981 and 1982, the P concentration in the ear leaf averaged 0.35% (w/w) and was n o t affected by treatments. In 1983, however, there was a starter fertilizer effect {Table III), i.e., leaf P levels were higher with than without the P-containing starters (0.47 vs. 0.43%, w/w). None of the leaf P concentrations would be considered deficient. TABLE III Concentration of P and K (%, w/w) in the ear leaf at early silking as affected by starter fertilizers Starter fertilizer N --P--K (kg ha-')

P

K

1983

1981

1982

1983

0--0--0 24--0--0 0--26--0 0--0--66 24--26--0 24--26--66

0.41 0.44 0.48 0.43 0.46 0.46

1.67 1.47 1.53 2.03 1.49 1.98

1.23 1.23 1.25 1.56 1.16 1.70

1.82 1.88 1.91 2.29 1.68 2.17

FLSD (0.10)

0.03

0.16

0.16

0.11

Potassium concentrations in the ear leaf (Table III) varied among starter fertilizer treatments, but not between tillage systems. The K effects were similar to those found in the y o u n g plant tissue, in that the primary responses occurred between K and no-K fertilizer. Average ear-leaf K concentrations were 2.00, 1.63 and 2.23% (w/w) in 1981, 1982 and 1983, respectively, when K was included in the starter fertilizer and 1.54, 1.22 and 1.82% (w/w) when it was n o t included. The ear-leaf K concentrations were within the suggested sufficiency range {1.75--2.25%, w/w) in 1981 and 1983, but not in 1982. In 1981, higher grain yields were obtained with strip tillage (5.6 t ha 1) than chisel-plow tillage (4.4 t ha-~), b u t there was no interaction between tillage and starter fertilizers. There was a yield response to the starter fertilizers (Table IV), but this response was primarily to N. The N--P--K starter, however, resulted in 9% higher yields than the N and N--P starter. In 1982, there were no differences in grain yields among tillage systems

141

and each of the starter fertilizers resulted in higher yields than the no-starter control (Table IV}. The greatest yield increase was due to N, but the N--P combination resulted in 8% higher yields than N alone. The rainfall distribution (Table V) was much better in 1983 than in 1981 TABLE IV Corn grain yield (t h a -~) as a f f e c t e d b y s t a r t e r fertilizers a n d tillage Starter fertilizers

1981

1982

1983 Chisel p l o w

None N P K N--P N--P--K

4.4 5.2 4.6 4.7 5.3 5.7

3.8 4.5 4.1 4.1 4.9 4.6

9.2 9.0 9.2 8.9 9.2 9.8

FLSD (0.10)

0.33

0.24

0.66

Strip till 9.1 10.0 9.3 8.1 10.4 11.1 0.66

TABLE V Rainfall ( r a m ) d u r i n g t h e c o r n g r o w i n g season Month

Wee k

Year 1981

1982

1983

April

1 2 3 4

118 0 26 11

61 4 80 80

28 75 8 0

May

1 2 3 4

7 4 32 88

0 19 6 29

5 0 12 3

June

1 2 3 4

7 75 0 0

0 5 0 32

34 5 103 36

July

1 2 3 4

43 22 a 0 0

3 15 a 28 4

36 0 14 22 a

a p h y s i o l o g i c a l m a t u r i t y o c c u r r e d d u r i n g t h e first 2 weeks o f J u l y in 1981 a n d 1 9 8 2 a n d in t h e last w e e k of J u l y in 1 9 8 3 .

142

or 1982 and yields were much higher {Table IV). In 1983, the main effects of tillage were not significant (P=0.10), but there was a starter fertilizer X tillage interaction. Within the chisel-plow system, none of the starters resulted in higher yields than the no-starter control, b u t in the strip-tillage system, the N-containing starters improved yields. As in 1981, the N--P--K starter resulted in higher yields than N or N--P. The yield responses to the starter fertilizers were most probably a result of improved early-season plant growth rates. In 1981 and 1983, only the Ncontaining starters improved plant heights and these starters were the only ones that improved yields. In both years, however, the N--P--K combination resulted in higher yields than the N or N--P combination. In 1982, only the N and N--P combinations resulted in greater plant heights than the control, but all N-containing starters improved yields. Applying either P alone or K alone did not affect early-season plant heights, but in 1982 they slightly improved yields (7%). In 1983, K alone decreased yields (12%) in the striptillage system. There is a possibility that the starter fertilizers were correcting nutrient deficiencies. Soil K levels were in the upper part of the medium soil test rating and the lower part of the high soil test rating, so yield responses to applied K were conceivable. However, the K concentrations in whole plant tissue 6 weeks after planting were not in the suggested deficiency range and the K concentrations in the ear leaf at silking were low only in 1982. Also, yield responses to K did not occur, except in 1982, unless K was applied with N. Since N was the primary nutrient responsible for improving yields, there is a possibility that the small amount of N in the starter was correcting an early-season N deficiency. However, the corn was planted after legume crops each year and 224 kg ha -* N was applied 6 weeks after planting. Although the N concentration in whole plant tissue was low 1 year, ear-leaf N levels were in the sufficiency range each year and the ear-leaf N levels were as high with no-N starters as they were with N starters. CONCLUSIONS

(1) Starter fertilizers should be used when corn is grown in conservationtillage systems. (2) The starter fertilizer will increase early season growth rates. The improved growth will most likely be due to N and n o t P or K. (3) The probability of grain yield improvements with starter fertilizers increases as the a m o u n t of soil disturbed during pre-plant tillage decreases. (4) As with early-season plant growth, greatest grain yield improvements are due to N in the starter. However, additional yield responses can be obtained by including K and especially P in the starter, even if residual soil P levels are high. (5) Using P or K starters w i t h o u t N will n o t enhance early-season plant growth or grain yields at maturity.

143 REFERENCES Arambarri, P. and Talibudeen, O., 1959a. Factors influencing the isotopically exchangeable phosphate in soils. Part II. The effect of base saturation with sodium and calcium in non-calcareous soils. Plant Soil, 11 : 355--363. Arambarri, P. and Talibudeen, O., 1959b. Factors influencing the isotopically exchangeable phosphate in soils. Part III. The effect of temperature in some calcareous soils. Plant Soil, 11: 364--376. Austin, M.E., 1972. Land resource regions and major land resource areas o f the United States. Soil Conserv. Serv., U.S. Dep. Agric., Agriculture Handbook 296, 82 pp. Ball, D.M., 1981. Alabama 1981 production guide for non-irrigated corn for grain. Alabama Coop. Ex. Serv., Auburn Univ., Auburn, AL, 6 pp. Bates, T.E., Miller, M.H. and Singh, D., 1966. Fertilizer placed with corn seed reexamined. Crops Soils, 18: 20. Bauder, J.W., Randall, G.W. and Swan, J.B., 1981, Continuous tillage: What it does to the soil. Crops Soils, 34: 15--17. Bauer, A. and Black, A.L., 1981. Soil carbon, nitrogen, and bulk density comparisons in two cropland tillage systems after 25 years and in virgin grassland. Soil Sci. Soc. Am. J., 45: 1166--1170. Beauchamp, E.G. and Lathwell, D.J., 1967. Root-zone temperature effects on the early development of maize. Plant Soil, 26: 224--234. Bertrand, A.R. and Kohnke, H., 1957. Subsoil conditions and their effects on oxygen supply and the growth of corn roots. Soil Sci. Soc. Am. Proc., 21 : 135--140. Blevins, R.L. and Cook, D., 1970. No-tillage - - Its influence on soil moisture and soil temperature. Univ. of Kentucky College of Agriculture Exp. Stn. Prog. Rep. 187, 3 pp. Blevins, R.L., Smith, M.S., Thomas, G.W. and Frye, W.W., 1983. Influence o f conservation tillage on soil properties. J. Soil Water Cons., 38: 301--305. Cassman, K.G. and Munns, D.N., 1980. Nitrogen mineralization as affected by soil moisture, temperature, and depth. Soil Sci. Soc. Am. J., 44: 1233--1237. Cope, J.T., Jr., Evans, C.E. and Williams, H.C., 1981. Soil test fertilizer recommendations for Alabama Crops. Alabama Agric. Exp. Stn. Auburn Univ., AL, Circ. 251, 55 pp. Dick, W.A., 1983. Organic carbon, nitrogen, and phosphorus concentrations and pH in soil profiles as affected by tillage intensity. Soil Sci. Soc. Am. J., 47: 102--107. Doran, J.W., 1980. Soil microbial and biochemical changes associated with reduced tillage. Soil Sci. Soc. Am. J., 44: 765--771. Ketcheson, J.W., 1968. Effect of controlled air and soil temperature and starter fertilizer on growth and nutrient composition of corn (Zea mays L.). Soil Sci. Soc. Am. Proc., 32: 531--534. Knoll, H.A., Lathwell, D.J. and Brady, N.C., 1964. The influence of root-zone temperature on the growth and nutrient composition of corn (Zea mays L.). Soil Sci. Soc. Am. Proc., 28: 400--403. Luxmoore, R.J. and Stolzy, L.H., 1972. Oxygen diffusion in the soil--plant system. V. Oxygen concentration and temperature effects on oxygen relations predicted for maize roots. Agron. J., 64: 720--725. Phillips, R.E., 1974. Soil water, evapotranspiration and soil temperature in no-tilled soil. In: Proceedings of a No-tillage Research Conference, at the University of Kentucky, Lexington, pp. 6--14. Plank, C.O., 1979. Plant analysis h a n d b o o k for Georgia. Univ. of Georgia Coop. Ext. Serv. Bull. 735, 65 pp. Reyes, D.M., Stolzy, L.H. and Labanauskas, C.K., 1977. Temperature and oxygen effects in soil on nutrient uptake in jojoba seedlings. Agron. J., 69: 647--650. Touchton, J.T. and Hargrove, W.L., 1983. Grain sorghum response to starter fertilizers. Better Crops Plant Food, 67 : 1--3.

144 Unger, P.W., 1978. Straw mulch effects on soil temperatures and sorghum germination and growth. Agron. J., 70: 858--863. Wallingford, W., 1978. Phosphorus in starter fertilizer. In: Phosphorus for Agriculture. Potash/Phosphate Inst., Atlanta, GA, pp. 62--79. Warrington, I.J. and Kanemasu, E.T., 1983. Corn growth response to temperature and photoperiod. I. Seedling emergence, tassel initiation, and anthesis. Agron. J., 75: 749--754.